JP4015350B2 - Methods for cyclization and trimerization of alkynes - Google Patents

Description

（式中、Ｒ^１及びＲ^２はそれぞれ独立して水素原子、アルキル基、シクロアルキル基、シクロアルケニル基、アリール基、アラルキル基、シリル基、置換シリル基又は複素環基を表し、Ｒ^４，Ｒ^５，Ｒ^６及びＲ^７はそれぞれ独立してアルキル基を表し、また、Ｒ^４とＲ^６とでメチレン鎖を形成していてもよく、更にまた、Ｒ^４，Ｒ^５及びＹとで、及び／又は、Ｒ^６，Ｒ^７及びＹとで複素環を形成していてもよく、Ｘはハロゲン原子を表し、Ｙは酸素原子、−ＮＲ^８−、硫黄原子、−ＰＲ^９−又は−Ｐ（＝Ｚ）Ｒ^１０−を表す（但し、Ｒ^８、Ｒ^９、及びＲ^１０はそれぞれ独立して水素原子又はアルキル基を表し、Ｚは酸素原子又は硫黄原子を表す。）。］
で示されるタンタル錯体を触媒として用いることを特徴とするアルキンの環化三量化方法に関する。
また、本発明は、前記タンタル錯体からなるアルキンの環化三量化用触媒に関する。
【０００５】
本発明者らは、従来の問題点を克服し得る新規なアルキンの環化三量化用触媒を開発してきたところ、五塩化タンタルから容易に誘導することができる、炭素−炭素三重結合を有する化合物を配位子として有するタンタル錯体が、アルキンの環化三量化反応において優れた触媒作用を有することを見出した。
【０００６】
本発明における炭素−炭素三重結合を有する化合物としては、炭素−炭素三重結合を分子中に有するものであって、当該三重結合の周囲がタンタル原子と結合するために立体的な障害を有さないものであればよく、好ましい炭素−炭素三重結合を有する化合物としては、次式［３］
Ｒ^１−Ｃ≡Ｃ−Ｒ^２ ［３］
（式中、Ｒ^１及びＲ^２はそれぞれ独立して水素原子、アルキル基、シクロアルキル基、シクロアルケニル基、アリール基、アラルキル基、シリル基、置換シリル基又は複素環基を表す。）
で表される化合物が挙げられる。
【０００７】
本発明のタンタル錯体は、さらにエーテル化合物、アミン類、スルフィド化合物、有機リン化合物などのタンタル原子に配位可能な原子を有する化合物を配位子として有することができる。好ましい配位子としてはエーテル化合物を挙げることができ、エーテル化合物としては、例えば、ジアルキルエーテル、ジアルコキシアルカンなどの鎖状エーテル、１，４−ジオキサンなどの環状エーテルなどが挙げられる。
【０００８】
上記一般式［３］及び［１］において、Ｒ^１，Ｒ^２で示されるアルキル基としては、例えば、炭素数が１〜２０、好ましくは１〜１０、より好ましくは１〜６の直鎖状又は分枝状のアルキル基が挙げられ、より具体的には、例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、第二級ブチル基、第三級ブチル基、ペンチル基、ヘキシル基などが挙げられる。
また、シクロアルキル基としては、例えば、炭素数３〜３０、好ましくは３〜２０、より好ましくは３〜１０の単環、多環又は縮合環式のシクロアルキル基が挙げられ、より具体的には、シクロプロピル基、シクロペンチル基、シクロヘキシル基、シクロオクチル基等が挙げられる。
シクロアルケニル基としては、前記したシクロアルキル基に１個以上の二重結合などの不飽和基を有するものが挙げられる。
アリール基としては、例えば、炭素数６〜３０、好ましくは６〜２０、より好ましくは６〜１５の単環、多環又は縮合環式の芳香族炭化水素基が挙げられ、より具体的には、例えば、フェニル基、トリル基、キシリル基、ナフチル基、メチルナフチル基、ビフェニル基等が挙げられる。
【０００９】
アラルキル基としては、例えば、炭素数７〜３０、好ましくは７〜２０、より好ましくは７〜１５の単環、多環又は縮合環式のアラルキル基が挙げられ、より具体的には、例えば、ベンジル基、フェネチル基、ナフチルメチル基、ナフチルエチル基等が挙げられる。
置換シリル基としては、シリル基の水素原子の１〜３個がアルキル基、アリール基等に置き換わったものが挙げられ、中でもトリアルキル置換体が好ましく、より具体的には、トリメチルシリル基、トリエチルシリル基、ｔ−ブチルジメチルシリル基等が挙げられる。
複素環基としては、環中に少なくとも１個以上の窒素原子、酸素原子又は硫黄原子を有し、１個の環の大きさが５〜２０員、好ましくは５〜１０員、より好ましくは５〜７員であって、シクロアルキル基、シクロアルケニル基又はアリール基などの炭素環式基と縮合していてもよい飽和又は不飽和の単環、多環又は縮合環式のものが挙げられ、より具体的には、例えば、ピリジル基、チエニル基、チアゾリル基、フリル基、ピペリジル基、ピペラジル基、モルホリノ基、イミダゾリル基、インドリル基、キノリル基、ピリミジニル基等が挙げられる。
【００１０】
一般式［１］において、Ｒ^４，Ｒ^５，Ｒ^６，Ｒ^７で示されるアルキル基としては、例えば、炭素数が１〜２０、好ましくは１〜１０、より好ましくは１〜６の直鎖状又は分枝状のアルキル基が挙げられ、より具体的には、例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、第二級ブチル基、第三級ブチル基、ペンチル基、ヘキシル基などが挙げられる。また、Ｒ^４とＲ^６とでメチレン鎖を形成している場合としては、例えば、Ｒ^４とＲ^６とでエチレン基、トリメチレン基、テトラメチレン基等を形成している場合が挙げられる。更にまた、Ｒ^４，Ｒ^５及びＹとで、及び／又は、Ｒ^６，Ｒ^７及びＹとで複素環を形成している場合としては、例えば、Ｒ^４，Ｒ^５及びＹとで、及び／又は、Ｒ^６，Ｒ^７及びＹとでピリジン環、テトラヒドロフラン環、テトラヒドロチオフェン環、チオフェン環、ホスホラン環等を形成している場合等が挙げられる。
【００１１】
一般式［１］において、Ｘで示されるハロゲン原子としては、例えば、塩素、臭素、沃素等が挙げられる。
また、一般式［１］において、Ｙで示される−ＮＲ^８−、−ＰＲ^９−、−Ｐ（＝Ｚ）Ｒ^１０−におけるＲ^８，Ｒ^９，Ｒ^１０で示されるアルキル基としては、前記Ｒ^４，Ｒ^５，Ｒ^６，Ｒ^７で示されるアルキル基と同様のものが挙げられる。
【００１２】
一般式［１］で示されるタンタル錯体の具体例としては、例えば、下記の如きものが挙げられる。
【００１３】
【化４】

【００１４】
一般式［１］で示されるタンタル錯体は、例えば五塩化タンタル、五臭化タンタル等から容易に合成することが出来る。
即ち、例えば、五塩化タンタルをトルエン等の炭化水素系溶媒中、亜鉛の存在下、１，２−ジメトキシエタン（ＤＭＥ）、ピリジン、テトラヒドロフラン（ＴＨＦ）、テトラヒドロチオフェン等と室温で３０〜６０分間反応させた後、一般式［３］
Ｒ^１−Ｃ≡Ｃ−Ｒ^２ ［３］
（式中、Ｒ^１，Ｒ^２は前記と同じ。）
で示されるアルキン類と２０〜８０℃で数時間反応させれば目的とするタンタル錯体触媒が容易に得られる。生成したタンタル錯体触媒は、これを単離した後、環化三量化反応に用いても良いが、単離せずにそのまま環化三量化に使用することもできる。
【００１５】
本発明の方法により環化三量化されるアルキンとしては、末端アルキンが好ましい。末端アルキンとしては、例えば下記一般式［２］
Ｒ^３−Ｃ≡ＣＨ ［２］
（式中、Ｒ^３はアルキル基、シクロアルキル基、シクロアルケニル基、アリール基、アラルキル基、シリル基、置換シリル基又は複素環基を表す。）
で示される末端アルキンが挙げられる。
なお、一般式［２］において、Ｒ^３で示されるアルキル基、シクロアルキル基、シクロアルケニル基、アリール基、アラルキル基、置換シリル基及び複素環基の定義及び具体例等はＲ^１，Ｒ^２のそれらと全く同じである。
【００１６】
本発明に係る環化三量化反応は、先ず、反応溶媒となる有機化合物中に一般式［１］で示されるタンタル錯体を添加し（或いは、タンタル錯体に反応溶媒となる有機化合物を加え）、これにアルキンを加えることにより進行する。反応溶媒としては、例えばベンゼン、トルエン、キシレン等の芳香族炭化水素、例えばヘキサン、石油エーテル等の脂肪族炭化水素、例えば塩化メチレン、ジクロルメタン、クロロホルム等のハロゲン化炭化水素、例えばジエチルエーテル、ジイソプロピルエーテル、ＴＨＦ等のエーテル系溶剤等が挙げられるが、同じアルキンを用いた場合の比較では、脂肪族炭化水素が反応が一番速く進行するので好ましい。
なお、アルキンそのものを反応溶媒として使用することも可能である。
タンタル錯体触媒の使用量は、反応に供するアルキンに対し、通常１ｍｏｌ％程度で充分である。
反応温度は、０〜２００℃の範囲の何れでもよいが、通常は室温付近の温度で行われる。反応時間は反応温度やアルキンの種類、その他の反応条件等により異なり、遅いものでは十数時間〜数十時間を要するものもあるが、速いものでは１〜２時間程度で充分である。
【００１７】
本発明の環化三量化反応は高い触媒活性で進行し、目的とする芳香族化合物のみを高収率で合成することができ、直鎖のアルキンオリゴマーは全く副生しない。 また、目的生成物は、反応液をシリカゲルカラムに通して触媒を除去した後、溶媒を減圧下留去するだけで簡単に単離することができる。
なお、本発明の環化三量化方法を実施するに際し、一般式［１］で示されるタンタル錯体として、Ｒ^１及びＲ^２が一般式［２］で示されるアルキンのＲ^３と同じ基である錯体を用いれば、目的生成物（１，３，５−トリ置換体と１，３，４−トリ置換体の合計）の収率はほぼ１００％となる。
【００１８】
【実施例】
次に実施例、参考例により本発明をより詳細に説明するが、本発明はこれらの実施例、参考例に限定されるものではない。
【００１９】
参考例１［ＴａＣｌ_３（ＥｔＣ≡ＣＥｔ）（ｄｍｅ）（タンタル錯体１）の合成］
シュレンク型反応容器に、アルゴン雰囲気下で五塩化タンタル９５９ｍｇ（２．６８ｍｍｏｌ）を仕込み、トルエンとＤＭＥをそれぞれ１３ｍＬ加えて撹拌した。薄黄色になった溶液に、五塩化タンタルに対して亜鉛を１．５当量（２７５ｍｇ、４．２１ｍｍｏｌ）加えると深緑色の懸濁液となった。２５℃で１時間撹拌した後、３−ヘキシンを五塩化タンタルに対して１当量（０．３０５ｍＬ、２．６８ｍｍｏｌ）加え、５０℃で２時間撹拌した。反応終了後、反応液を遠心分離して塩化亜鉛などの不溶物を除き、上澄液（橙色）の溶媒を減圧下で留去した。残渣をトルエン４５ｍＬに溶解し、その溶液を３０ｍＬまで濃縮して、遠心分離し、上澄液を−２０℃で２日間静置した。析出晶を濾取し、橙色のタンタル錯体１ ８０１ｍｇ（１．７４ｍｍｏｌ、６５％）を得た。
ｍｐ：１２９−１３０℃(dec)。
ＩＲ（nujol/CsI、ｃｍ^−１）：１６２２（^νＣ≡Ｃ，coordinated）、３１２（^ν Ｔａ−Ｃｌ）。
^１Ｈ ＮＭＲ（Ｃ_６Ｄ_５ＣＤ_３）δ：
1.37(t, J=7.5Hz, 6H), 3.10-3.17(m, 4H), 3.13(s, 3H), 3.59(s, 3H), 3. 60(q, J=7.5Hz, 4H)。
^１３Ｃ ＮＭＲ（ＣＤ_２Ｃｌ_２）δ：
13.2, 33.3, 62.1, 68.9, 70.6, 76.4, 256.0。
元素分析（Ｃ_１０Ｈ_２０Ｏ_２ＴａＣｌ_３として）
計算値：Ｃ，２６．１４； Ｈ，４．３９
実測値：Ｃ，２５．９２； Ｈ，４．４７。
【００２０】
参考例２［ＴａＣｌ_３（Ｍｅ_３ＳｉＣ≡ＣＨ）（ｄｍｅ）（タンタル錯体２）の合成］
シュレンク型反応容器に、アルゴン雰囲気下で五塩化タンタル５９４ｍｇ（１．６６ｍｍｏｌ）を仕込み、トルエンとＤＭＥをそれぞれ１２ｍＬ加えて撹拌した。薄黄色になった溶液に、亜鉛を五塩化タンタルに対して１．５当量（１６３ｍｇ、２．４９ｍｍｏｌ）加えると深緑色の懸濁液となった。２５℃で１時間撹拌した後、トリメチルシリルアセチレンを五塩化タンタルに対して１当量（０．２３５ｍＬ、１．６６ｍｍｏｌ）加えて、２５℃で２時間撹拌した。反応終了後、反応液を遠心分離して塩化亜鉛などの不溶物を除き、上澄液（暗赤色）の溶媒を減圧下で留去して、薄茶色の固体を得た。これをトルエン１５ｍＬに溶解したのち遠心分離した。上澄液にヘキサン２０ｍＬを加え、−２０℃で１日静置した後、析出晶を濾取し、褐色のタンタル錯体２ １７４ｍｇ（０．３７ｍｍｏｌ、２２％）を得た。
ｍｐ：１０５℃（ｄｅｃ）。
ＩＲ（nujol/CsI、ｃｍ^−１）：１５５６（^νＣ≡Ｃ）、３０９（^νＴａ−Ｃｌ）。
^１Ｈ ＮＭＲ（Ｃ_６Ｄ_６）δ：
15.15(s, 1H), 3.68(s, 3H), 3.32(s, 3H), 3.10(s, 4H), 0.61(s, 9H)。
^１３Ｃ ＮＭＲ（Ｃ_６Ｄ_６）δ：
255.3, 239.1, 75.4, 70.9, 68.4, 62.6, 0.3。
【００２１】
実施例１（１−ヘキシンの環化三量化反応）
シュレンク型反応容器に、アルゴン雰囲気下でタンタル錯体１ ３４．８ｍｇ（０．０７５７ｍｍｏｌ）を仕込み、これにトルエン５ｍＬを加えると黄色の溶液になった。これに１−ヘキシンをタンタル錯体１に対して１００当量（０．８７ｍＬ、７，５７ｍｍｏｌ）加えて、２５℃で１８時間撹拌反応させた。反応後の反応液は黄色のままであった。そのあと、錯体１を除くため、空気雰囲気下でシリカゲルを少量加えて錯体１を分解した。このとき、反応液は無色となった。反応液をショートカラムに通して錯体１の分解物を除き、溶媒を減圧下で留去することにより、環化三量体のトリブチルベンゼン６２０ｍｇ（２．５２ｍｍｏｌ、収率１００％）を得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝７２／２８。
なお、環化三量体の異性体比は^１Ｈ ＮＭＲとＧＣにより解析した。
^１Ｈ ＮＭＲ（ＣＤＣｌ_３）δ：
0.90-0.97(m, 9H), 1.34-1.41(m, 6H), 1.54-1.58(m, 6H), 2.52-2.58(m,6 H), 6.81-7.05(3H; 1,2,4-Bu_３C_６H_３:6.93(d, J=7.8Hz, 1H), 6.95(s, 1H),7. 04(d，J=7.8Hz, 1H), 1,3,5-Bu_３C_６H_３:6.81(s, 3H))。
【００２２】
実施例２（１−ヘキシンの環化三量化反応）
実施例１において、１−ヘキシンをタンタル錯体１に対して１００当量使用する代わりに１当量使用し、反応時間を２０時間とした以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを６３％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝６５／３５。
【００２３】
実施例３（１−ヘキシンの環化三量化反応）
実施例１において、１−ヘキシンをタンタル錯体１に対して１００当量使用する代わりに５当量使用した以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを６７％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝７４／２６。
【００２４】
実施例４（１−ヘキシンの環化三量化反応）
実施例１において、反応溶媒をトルエンからヘキサンに代え、反応時間を１．５時間とした以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを１００％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝７６／２４。
【００２５】
実施例５（１−ヘキシンの環化三量化反応）
実施例１において、反応溶媒をトルエンから塩化メチレンに代え、反応時間を１．５時間とした以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを８８％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝６８／３２。
【００２６】
実施例６（１−ヘキシンの環化三量化反応）
実施例１において、反応時間を１．５時間とした以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを７４％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝７１／２９。
【００２７】
実施例７（フェニルアセチレンの環化三量化反応）
実施例１において、１−ヘキシンをタンタル錯体１に対して１００当量使用する代わりにフェニルアセチレンをタンタル錯体１に対して１００当量使用し、反応時間を２０時間とした以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリフェニルベンゼンを９３％の収率で得た。異性体比：１，２，４−（Ｃ_６Ｈ_５）_３Ｃ_６Ｈ_３／１，３，５−（Ｃ_６Ｈ_５）_３Ｃ_６Ｈ_３＝５８／４２。
【００２８】
実施例８（トリメチルシリルアセチレンの環化三量化反応）
実施例１において、１−ヘキシンをタンタル錯体１に対して１００当量使用する代わりにトリメチルシリルアセチレンをタンタル錯体１に対して１００当量使用し、反応溶媒としてヘキサンを用いた以外は実施例１と全く同様にして反応及び後処理を行い、環化三量体のトリ（トリメチルシリル）ベンゼンを１００％の収率で得た。異性体比：１，２，４−（Ｍｅ_３Ｓｉ）_３Ｃ_６Ｈ_３／１，３，５−（Ｍｅ_３Ｓｉ）_３Ｃ_６Ｈ_３＝５２／４８。
^１Ｈ ＮＭＲ（ＣＤＣｌ_３）δ：
0.29(S, 27H), 7.49-7.84(3H; 1,2,4-(Me_３Si)_３C_６H_３:7.49(d, J=7.4Hz, 1H), 7.65(d, J=7.4Hz, 1H), 7.84(s, 1H), 1,3,5-(Me_３Si)_３C_６H_３:7.69(s, 3H))。
【００２９】
実施例９（１−ヘキシンの環化三量化反応）
実施例２において、タンタル錯体１：ＴａＣｌ_３（ＥｔＣ≡ＣＥｔ）（ｄｍｅ）の代わりにタンタル錯体：ＴａＣｌ_３（ＰｈＣ≡ＣＭｅ）（ｄｍｅ）を使用した以外は実施例２と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを４０％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝７３／２７。
【００３０】
実施例１０（１−ヘキシンの環化三量化反応）
実施例６において、タンタル錯体１：ＴａＣｌ_３（ＥｔＣ≡ＣＥｔ）（ｄｍｅ）の代わりにタンタル錯体：ＴａＣｌ_３（ＥｔＣ≡ＣＥｔ）（ｐｙ）_２（参考例１において、ＤＭＥの代わりにピリジンを使用して合成した。）を使用した以外は実施例６と全く同様にして反応及び後処理を行い、環化三量体のトリブチルベンゼンを５６％の収率で得た。異性体比：１，２，４−Ｂｕ_３Ｃ_６Ｈ_３／１，３，５−Ｂｕ_３Ｃ_６Ｈ_３＝４４／５６。
【００３１】
【発明の効果】
本発明に係るアルキンの環化三量化方法の利点としては、例えば下記の点等が挙げられる。
（１）使用する触媒の触媒活性が高い。
（２）触媒が容易に合成できる。
（３）反応収率がよい。
（４）副生物がなく、目的生成物の選択性が大である。
（５）触媒製造時、触媒を単離せず、そのまま反応に供することが出来る。
（６）原料（Ｒ−アルキン）と同一の置換基（Ｒ）を導入したタンタル錯体を用いることによって、目的芳香族化合物の収率を１００％に持っていくことが出来る。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an aromatic compound by cyclization trimerization of an alkyne and a catalyst therefor. Specifically, the present invention relates to a method for producing an aromatic compound by cyclization trimerization of an alkyne using a tantalum complex as a catalyst and the catalyst.
[0002]
[Prior art]
The greatest advantage of the method for producing an aromatic compound by cyclization trimerization of alkyne is that the aromatic compound has more various substituents than the method in which the substituent is introduced by direct substitution reaction to the aromatic compound. The compound is obtained.
Aromatic compounds obtained by cyclization and trimerization of substituted alkynes are useful as intermediates for petrochemical products, functional compounds, etc., since those having various substituents can be obtained. A compound.
Therefore, various proposals have been made so far for catalysts for cyclotrimerization of substituted alkynes.
That is, in a relatively old thing, for example, Ni (CO) ₂ (PPh ₃ ) ₂ [J. Org. Chem. , 26 , 5155 (1961)], TaCl ₅ [Bull. Chem. Soc. Jpn. , 53 , 1152 (1980), Ta ₂ Cl ₆ (SC ₄ H ₈ ) ₃ [J. Macromolecules, 14 , 233 (1981)], CpNbCl ₄ / Mg [Organometallics, 8 , 1566 (1989)] and the like have been proposed, and relatively new catalysts include, for example, Organometallics, 12 , 2911 ( 1993), J. et al. Am. Chem. Soc. 117 , 3008 (1995), J. MoI. Am. Chem. Soc. , 120 , 5130 (1998), J. Am. Am. Chem. Soc. , 121 , 7941 (1999), and the like, respectively, reports catalysts for cyclotrimerization of substituted alkynes.
However, each of these existing catalysts has problems such as low catalytic activity, catalyst preparation is not always easy, reaction yield is poor, linear by-product is generated, and selectivity of the target product is low. It is desired to develop a novel catalyst that has all of these points and does not have these problems.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the current situation as described above, and has high catalytic activity, easy catalyst preparation, good reaction yield, no by-products, and high selectivity of the target product. It is an object to provide a substituted alkyne cyclization trimerization catalyst and a method for producing an aromatic compound using the same.
[0004]
[Means for Solving the Problems]
The present invention relates to a cyclization trimerization method of alkyne, characterized in that a tantalum complex having a compound having a carbon-carbon triple bond as a ligand is used as a catalyst.
More specifically, the present invention relates to the general formula [1]
[Chemical 3]

(Wherein R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, a silyl group, a substituted silyl group or a heterocyclic group, R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents an alkyl group, and R ⁴ and R ⁶ may form a methylene chain, and further R ⁴ , R ⁵ and Y are And / or R ⁶ , R ⁷ and Y may form a heterocyclic ring, X represents a halogen atom, Y represents an oxygen atom, —NR ⁸ —, a sulfur atom, —PR ⁹ — or —P. (= Z) R ¹⁰ -is represented (however, R ⁸ , R ⁹ , and R ¹⁰ each independently represents a hydrogen atom or an alkyl group, and Z represents an oxygen atom or a sulfur atom).]
The tantalum cyclization trimerization method characterized by using the tantalum complex shown by these as a catalyst.
The present invention also relates to a catalyst for cyclization trimerization of alkyne comprising the tantalum complex.
[0005]
The present inventors have developed a novel alkyne cyclization trimerization catalyst capable of overcoming the conventional problems. A compound having a carbon-carbon triple bond that can be easily derived from tantalum pentachloride. It has been found that a tantalum complex having as a ligand has an excellent catalytic action in a cyclization trimerization reaction of an alkyne.
[0006]
The compound having a carbon-carbon triple bond in the present invention has a carbon-carbon triple bond in the molecule and has no steric hindrance because the periphery of the triple bond is bonded to a tantalum atom. Any compound having a preferable carbon-carbon triple bond may be used as the following formula [3]:
R ¹ —C≡C—R ² [3]
(In the formula, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, a silyl group, a substituted silyl group, or a heterocyclic group.)
The compound represented by these is mentioned.
[0007]
The tantalum complex of the present invention can further have a compound having an atom capable of coordinating with a tantalum atom, such as an ether compound, an amine, a sulfide compound, or an organic phosphorus compound, as a ligand. Preferred ligands include ether compounds. Examples of ether compounds include chain ethers such as dialkyl ethers and dialkoxyalkanes, and cyclic ethers such as 1,4-dioxane.
[0008]
In the above general formulas [3] and [1], the alkyl group represented by R ¹ and R ² is, for example, a straight chain having 1 to 20, preferably 1 to 10, more preferably 1 to 6 carbon atoms. Or a branched alkyl group, and more specifically, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, secondary butyl group, tertiary butyl group, pentyl Group, hexyl group and the like.
Examples of the cycloalkyl group include monocyclic, polycyclic or condensed cyclic cycloalkyl groups having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms. Includes a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and the like.
Examples of the cycloalkenyl group include those having an unsaturated group such as one or more double bonds in the aforementioned cycloalkyl group.
Examples of the aryl group include monocyclic, polycyclic or condensed cyclic aromatic hydrocarbon groups having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 6 to 15 carbon atoms, and more specifically. Examples thereof include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a methylnaphthyl group, and a biphenyl group.
[0009]
Examples of the aralkyl group include monocyclic, polycyclic or condensed cyclic aralkyl groups having 7 to 30 carbon atoms, preferably 7 to 20 carbon atoms, more preferably 7 to 15 carbon atoms. Examples include a benzyl group, a phenethyl group, a naphthylmethyl group, and a naphthylethyl group.
Examples of the substituted silyl group include those in which 1 to 3 hydrogen atoms of the silyl group are replaced by alkyl groups, aryl groups, etc. Among them, trialkyl substituents are preferred, and more specifically, trimethylsilyl groups, triethylsilyl groups, and the like. Group, t-butyldimethylsilyl group and the like.
The heterocyclic group has at least one nitrogen atom, oxygen atom or sulfur atom in the ring, and the size of one ring is 5 to 20 members, preferably 5 to 10 members, more preferably 5 A saturated or unsaturated monocyclic, polycyclic or condensed ring which may be condensed with a carbocyclic group such as a cycloalkyl group, a cycloalkenyl group or an aryl group, More specifically, examples include a pyridyl group, a thienyl group, a thiazolyl group, a furyl group, a piperidyl group, a piperazyl group, a morpholino group, an imidazolyl group, an indolyl group, a quinolyl group, and a pyrimidinyl group.
[0010]
In the general formula [1], the alkyl group represented by R ⁴ , R ⁵ , R ⁶ , R ⁷ is, for example, a straight chain having 1 to 20, preferably 1 to 10, more preferably 1 to 6 carbon atoms. And more specifically, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, secondary butyl group, tertiary butyl group, A pentyl group, a hexyl group, etc. are mentioned. Examples of the case where R ⁴ and R ⁶ form a methylene chain include the case where R ⁴ and R ⁶ form an ethylene group, trimethylene group, tetramethylene group, or the like. Furthermore, when a heterocyclic ring is formed with R ⁴ , R ⁵ and Y and / or with R ⁶ , R ⁷ and Y, for example, with R ⁴ , R ⁵ and Y, and And / or the case where R ⁶ , R ⁷ and Y form a pyridine ring, tetrahydrofuran ring, tetrahydrothiophene ring, thiophene ring, phosphorane ring or the like.
[0011]
In the general formula [1], examples of the halogen atom represented by X include chlorine, bromine, iodine and the like.
In the general formula [1], the alkyl groups represented by R ⁸ , R ⁹ and R ¹⁰ in —NR ⁸ —, —PR ⁹ —, and —P (═Z) R ¹⁰ — represented by Y include ^{R 4, R 5, R 6} , those similar to the alkyl group represented by ^{R 7} can be exemplified.
[0012]
Specific examples of the tantalum complex represented by the general formula [1] include the following.
[0013]
[Formula 4]

[0014]
The tantalum complex represented by the general formula [1] can be easily synthesized from, for example, tantalum pentachloride, tantalum pentabromide or the like.
That is, for example, tantalum pentachloride is reacted with 1,2-dimethoxyethane (DME), pyridine, tetrahydrofuran (THF), tetrahydrothiophene, etc. in a hydrocarbon solvent such as toluene at room temperature for 30 to 60 minutes. After the general formula [3]
R ¹ —C≡C—R ² [3]
(Wherein R ¹ and R ² are the same as described above.)
The target tantalum complex catalyst can be easily obtained by reacting with the alkynes represented by formula (2) at 20 to 80 ° C. for several hours. The produced tantalum complex catalyst may be isolated and then used for the cyclization trimerization reaction, but can also be used for the cyclization trimerization without isolation.
[0015]
As the alkyne cyclized and trimerized by the method of the present invention, a terminal alkyne is preferable. As the terminal alkyne, for example, the following general formula [2]
R ³ —C≡CH [2]
(In the formula, R ³ represents an alkyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, a silyl group, a substituted silyl group, or a heterocyclic group.)
The terminal alkyne shown by these is mentioned.
Incidentally, in the general formula [2], the alkyl group represented by R ^3, a cycloalkyl group, a cycloalkenyl group, an aryl group, defined and specific examples such as aralkyl group, a substituted silyl group and the heterocyclic group R ^1, R ² Are exactly the same as those in
[0016]
In the cyclization trimerization reaction according to the present invention, first, the tantalum complex represented by the general formula [1] is added to the organic compound serving as the reaction solvent (or the organic compound serving as the reaction solvent is added to the tantalum complex). It progresses by adding alkyne to this. Examples of the reaction solvent include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane and petroleum ether, halogenated hydrocarbons such as methylene chloride, dichloromethane and chloroform, such as diethyl ether and diisopropyl ether. An ether solvent such as THF can be used, but in the comparison using the same alkyne, an aliphatic hydrocarbon is preferable because the reaction proceeds most rapidly.
The alkyne itself can be used as a reaction solvent.
The amount of the tantalum complex catalyst used is usually about 1 mol% with respect to the alkyne used for the reaction.
The reaction temperature may be in the range of 0 to 200 ° C., but is usually performed at a temperature near room temperature. The reaction time varies depending on the reaction temperature, the type of alkyne, other reaction conditions, and the like, and some of the slow ones require 10 to several tens of hours, but about 1 to 2 hours are sufficient for the fast ones.
[0017]
The cyclization trimerization reaction of the present invention proceeds with high catalytic activity, and only the desired aromatic compound can be synthesized in high yield, and no linear alkyne oligomer is produced as a by-product. The target product can be easily isolated by simply passing the reaction solution through a silica gel column to remove the catalyst and then distilling off the solvent under reduced pressure.
In carrying out the cyclization trimerization method of the present invention, as the tantalum complex represented by the general formula [1], R ¹ and R ² are the same group as the R ^{3 of the} alkyne represented by the general formula [2]. When the complex is used, the yield of the target product (total of 1,3,5-trisubstituted product and 1,3,4-trisubstituted product) is almost 100%.
[0018]
【Example】
EXAMPLES Next, although an Example and a reference example demonstrate this invention in detail, this invention is not limited to these Examples and a reference example.
[0019]
Reference Example 1 [Synthesis of TaCl ₃ (EtC≡CEt) (dme) (tantalum complex 1)]
In a Schlenk type reaction vessel, 959 mg (2.68 mmol) of tantalum pentachloride was charged under an argon atmosphere, and 13 mL each of toluene and DME were added and stirred. When 1.5 equivalents (275 mg, 4.21 mmol) of zinc with respect to tantalum pentachloride was added to the light yellow solution, a deep green suspension was obtained. After stirring at 25 ° C. for 1 hour, 1 equivalent (0.305 mL, 2.68 mmol) of 3-hexyne was added to tantalum pentachloride, and the mixture was stirred at 50 ° C. for 2 hours. After completion of the reaction, the reaction solution was centrifuged to remove insoluble matters such as zinc chloride, and the supernatant (orange) solvent was distilled off under reduced pressure. The residue was dissolved in 45 mL of toluene, the solution was concentrated to 30 mL, centrifuged, and the supernatant was allowed to stand at −20 ° C. for 2 days. The precipitated crystals were collected by filtration to obtain 801 mg (1.74 mmol, 65%) of an orange tantalum complex 1.
mp: 129-130 ° C. (dec).
IR (nujol / CsI, cm ⁻¹ ): 1622 ( ^ν C≡C, coordinated), 312 ( ^ν Ta—Cl).
¹ H NMR (C ₆ D ₅ CD ₃ ) δ:
1.37 (t, J = 7.5Hz, 6H), 3.10-3.17 (m, 4H), 3.13 (s, 3H), 3.59 (s, 3H), 3.60 (q, J = 7.5Hz, 4H).
¹³ C NMR (CD ₂ Cl ₂ ) δ:
13.2, 33.3, 62.1, 68.9, 70.6, 76.4, 256.0.
Elemental analysis _{(as C 10 H 20 O 2 TaCl 3} )
Calculated value: C, 26.14; H, 4.39
Found: C, 25.92; H, 4.47.
[0020]
Reference Example 2 [Synthesis of TaCl ₃ (Me ₃ SiC≡CH) (dme) (tantalum complex 2)]
In a Schlenk type reaction vessel, 594 mg (1.66 mmol) of tantalum pentachloride was charged in an argon atmosphere, and 12 mL of toluene and DME were added and stirred. When 1.5 equivalents (163 mg, 2.49 mmol) of zinc to tantalum pentachloride was added to the light yellow solution, a deep green suspension was obtained. After stirring at 25 ° C. for 1 hour, 1 equivalent (0.235 mL, 1.66 mmol) of trimethylsilylacetylene was added to tantalum pentachloride, and the mixture was stirred at 25 ° C. for 2 hours. After completion of the reaction, the reaction solution was centrifuged to remove insoluble matters such as zinc chloride, and the supernatant (dark red) solvent was distilled off under reduced pressure to obtain a light brown solid. This was dissolved in 15 mL of toluene and centrifuged. After adding 20 mL of hexane to the supernatant and allowing to stand at −20 ° C. for 1 day, the precipitated crystals were collected by filtration to obtain 174 mg (0.37 mmol, 22%) of a brown tantalum complex.
mp: 105 ° C. (dec).
IR (nujol / CsI, cm ⁻¹ ): 1556 ( ^ν C≡C), 309 ( ^ν Ta—Cl).
¹ H NMR (C ₆ D ₆ ) δ:
15.15 (s, 1H), 3.68 (s, 3H), 3.32 (s, 3H), 3.10 (s, 4H), 0.61 (s, 9H).
¹³ C NMR (C ₆ D ₆ ) δ:
255.3, 239.1, 75.4, 70.9, 68.4, 62.6, 0.3.
[0021]
Example 1 (Cyclotrimerization reaction of 1-hexyne)
A Schlenk reaction vessel was charged with 34.8 mg (0.0757 mmol) of tantalum complex 1 under an argon atmosphere, and when 5 mL of toluene was added thereto, a yellow solution was obtained. To this, 100 equivalents (0.87 mL, 7,57 mmol) of 1-hexyne was added to tantalum complex 1, and the mixture was stirred at 25 ° C. for 18 hours. The reaction solution after the reaction remained yellow. Thereafter, in order to remove the complex 1, a small amount of silica gel was added in an air atmosphere to decompose the complex 1. At this time, the reaction solution became colorless. The reaction solution was passed through a short column to remove the decomposition product of complex 1, and the solvent was distilled off under reduced pressure to obtain 620 mg (2.52 mmol, yield 100%) of cyclized trimer tributylbenzene. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 72/28.
The isomer ratio of the cyclized trimer was analyzed by ¹ H NMR and GC.
¹ H NMR (CDCl ₃ ) δ:
0.90-0.97 (m, 9H), 1.34-1.41 (m, 6H), 1.54-1.58 (m, 6H), 2.52-2.58 (m, 6 H), 6.81-7.05 (3H; 1,2,4-Bu ₃ C ₆ H ₃ : 6.93 (d, J = 7.8Hz, 1H), 6.95 (s, 1H), 7.04 (d, J = 7.8Hz, 1H), 1,3,5-Bu ₃ C ₆ H ₃ : 6.81 (s, 3H)).
[0022]
Example 2 (Cyclotrimerization reaction of 1-hexyne)
In Example 1, instead of using 100 equivalents of 1-hexyne with respect to tantalum complex 1, 1 equivalent was used, and the reaction and post-treatment were performed in the same manner as in Example 1 except that the reaction time was 20 hours. The cyclized trimer tributylbenzene was obtained in 63% yield. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 65/35.
[0023]
Example 3 (Cyclotrimerization reaction of 1-hexyne)
In Example 1, the reaction and post-treatment were performed in the same manner as in Example 1 except that 5 equivalents of 1-hexyne were used instead of 100 equivalents relative to tantalum complex 1, and cyclized trimer tributylbenzene In 67% yield. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 74/26.
[0024]
Example 4 (Cyclotrimerization reaction of 1-hexyne)
In Example 1, the reaction and the post-treatment were performed in the same manner as in Example 1 except that the reaction solvent was changed from toluene to hexane and the reaction time was 1.5 hours. % Yield. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 76/24.
[0025]
Example 5 (Cyclotrimerization reaction of 1-hexyne)
In Example 1, the reaction and the post-treatment were performed in the same manner as in Example 1 except that the reaction solvent was changed from toluene to methylene chloride and the reaction time was 1.5 hours. Obtained in 88% yield. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 68/32.
[0026]
Example 6 (Cyclotrimerization reaction of 1-hexyne)
In Example 1, the reaction and post-treatment were performed in the same manner as in Example 1 except that the reaction time was 1.5 hours, and cyclized trimer tributylbenzene was obtained in a yield of 74%. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 71/29.
[0027]
Example 7 (Cyclization trimerization reaction of phenylacetylene)
In Example 1, instead of using 100 equivalents of 1-hexyne relative to tantalum complex 1, 100 equivalents of phenylacetylene relative to tantalum complex 1 were used, and the reaction time was 20 hours. Exactly the same as in Example 1. The reaction and post-treatment were carried out to obtain cyclized trimer triphenylbenzene in 93% yield. Isomer _{ratio: 1,2,4- (C 6 H 5)} 3 C 6 H 3 / 1,3,5- (C 6 H 5) 3 C 6 H 3 = 58/42.
[0028]
Example 8 (Cyclotrimerization of trimethylsilylacetylene)
In Example 1, instead of using 100 equivalents of 1-hexyne relative to tantalum complex 1, 100 equivalents of trimethylsilylacetylene relative to tantalum complex 1 were used, and hexane was used as the reaction solvent. The reaction and post-treatment were carried out to obtain cyclized trimer tri (trimethylsilyl) benzene in a yield of 100%. Isomer ratio: 1,2,4- (Me ₃ Si) ₃ C ₆ H ₃ / 1,3,5- (Me ₃ Si) ₃ C ₆ H ₃ = 52/48.
¹ H NMR (CDCl ₃ ) δ:
0.29 (S, 27H), 7.49-7.84 (3H; 1,2,4- (Me ₃ Si) ₃ C ₆ H ₃ : 7.49 (d, J = 7.4Hz, 1H), 7.65 (d, J = 7.4Hz , 1H), 7.84 (s, 1H), 1,3,5- (Me ₃ Si) ₃ C ₆ H ₃ : 7.69 (s, 3H)).
[0029]
Example 9 (Cyclotrimerization of 1-hexyne)
In Example 2, the reaction and reaction were carried out in the same manner as in Example 2 except that the tantalum complex 1: TaCl ₃ (PhC≡CMe) (dme) was used instead of the tantalum complex 1: TaCl ₃ (EtC≡CEt) (dme). Post-treatment was performed to obtain cyclized trimer tributylbenzene in 40% yield. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 73/27.
[0030]
Example 10 (Cyclotrimerization of 1-hexyne)
In Example 6, tantalum complex 1: TaCl ₃ (EtC≡CEt) (dme) instead of tantalum complex: TaCl ₃ (EtC≡CEt) (py) ₂ (In Reference Example 1, pyridine was used instead of DME) The cyclized trimer tributylbenzene was obtained in a yield of 56% in exactly the same manner as in Example 6 except that was used. Isomer ratio: 1,2,4-Bu ₃ C ₆ H ₃ / 1,3,5-Bu ₃ C ₆ H ₃ = 44/56.
[0031]
【The invention's effect】
Advantages of the alkyne cyclization trimerization method according to the present invention include, for example, the following points.
(1) The catalytic activity of the catalyst used is high.
(2) The catalyst can be easily synthesized.
(3) The reaction yield is good.
(4) There is no by-product and the selectivity of the target product is great.
(5) During catalyst production, the catalyst can be used as it is without isolation.
(6) By using the tantalum complex introduced with the same substituent (R) as the raw material (R-alkyne), the yield of the target aromatic compound can be brought to 100%.

Claims (10)

In the terminal alkyne cyclization trimerization method using as a catalyst a tantalum complex having a compound having a carbon-carbon triple bond as a ligand, a terminal used for the reaction using a tantalum complex represented by the following general formula [1] as a catalyst A method for cyclization and trimerization of terminal alkyne, which is used in an amount of 1 to 20 mol% based on alkyne.

[Wherein, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, a silyl group, or a substituted silyl group, and R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents an alkyl group. Here, the substituted silyl group represents a silyl group in which 1 to 3 silyl groups are substituted with an alkyl group or an aryl group. R ⁴ and R ⁶ may form a methylene chain, and R ⁴ , R ⁵ and Y and / or R ⁶ , R ⁷ and Y form a heterocyclic ring. X represents a halogen atom, and Y represents an oxygen atom, —NR ⁸ —, a sulfur atom, —PR ⁹ — or —P (═Z) R ¹⁰ — (provided that R ⁸ , R ⁹ , And R ¹⁰ each independently represents a hydrogen atom or an alkyl group, and Z represents an oxygen atom or a sulfur atom. ]   The method according to claim 1, wherein Y in the general formula [1] is an oxygen atom.   The method according to claim 1 or 2, wherein X in the general formula [1] is a chlorine atom. The method according to any one of claims 1 to 3, wherein, in the general formula [1], R ⁴ and R ⁶ are combined to form an ethylene group. The method according to any one of claims 1 to 4, wherein R ¹ and R ² in the general formula [1] are the same group. A catalyst for cyclization trimerization of terminal alkyne, comprising a tantalum complex having a compound having a carbon-carbon triple bond as a ligand, the amount used for the terminal alkyne used for the reaction is 1 to 20 mol%, the following general A tantalum complex catalyst represented by the formula [1].

[Wherein, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, a silyl group, or a substituted silyl group, and R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents an alkyl group. Here, the substituted silyl group represents a silyl group in which 1 to 3 silyl groups are substituted with an alkyl group or an aryl group. R ⁴ and R ⁶ may form a methylene chain, and R ⁴ , R ⁵ and Y and / or R ⁶ , R ⁷ and Y form a heterocyclic ring. X represents a halogen atom, and Y represents an oxygen atom, —NR ⁸ —, a sulfur atom, —PR ⁹ — or —P (═Z) R ¹⁰ — (provided that R ⁸ , R ⁹ , And R ¹⁰ each independently represents a hydrogen atom or an alkyl group, and Z represents an oxygen atom or a sulfur atom. ]   The catalyst according to claim 6, wherein Y in the general formula [1] is an oxygen atom.   The catalyst according to claim 6 or 7, wherein X in the general formula [1] is a chlorine atom. The catalyst according to any one of claims 6 to 8, wherein in the general formula [1], R ⁴ and R ⁶ are combined to form an ethylene group. The catalyst according to any one of claims 6 to 9, wherein R ¹ and R ² in the general formula [1] are the same group.