CN107805221A - Method for preparing 1H-indazole derivative - Google Patents

Abstract

The invention discloses a method for preparing 1H-indazole derivatives, wherein a compound of formula (A1) or a compound of formula (A2) is used as a raw material, and a compound of formula (B) is obtained by nitration reaction or halogenation reaction; a nitro group on the compound of formula (B) is reduced to obtain a compound of formula (C); a compound of formula (C) is used as a raw material, and in the presence of nitrite, a 1H-indazole derivative of formula (I) is obtained by diazotization and cyclization reaction. Compared with the existing method, the method of the invention can synthesize a variety of 1H-indazole derivatives, and the synthesis route is short, the yield is high, and it is more suitable for industrial production.

Description

A kind of method for preparing 1H-indazole derivative

technical field

The present invention relates to a method for preparing 1H-indazole derivatives.

Background technique

Indazole is a very important class of pharmaceutical intermediates. Indazole derivatives have a wide range of biological activities, such as anti-inflammatory, analgesic and antipyretic, regulation of protease activity and protein kinase, dopamine antagonism, anti-virus and anti-tumor, etc. Indazole, as the biological isostere of indole, is a ten-π-electron aromatic heterocyclic ring system. The unique structure and properties of indazole compounds make them have a very wide range of important uses in many fields, and the research on their properties and uses has attracted more and more attention from synthetic chemists and pharmacologists.

However, there are few reports on the synthesis of 4,6-disubstituted 1H-indazole derivatives. Among the 4-nitro (or amino)-1H-indazole compounds substituted at the 6-position, there are only reports on the synthesis of compounds whose 6-position is bromine, and the synthesis route is long and the overall yield is low. With the rapid development of the pharmaceutical industry, 4,6-disubstituted 1H-indazole derivatives have received more and more attention as an important pharmaceutical intermediate. Research and development of an efficient synthetic method suitable for industrial production , can effectively reduce the production cost of this type of compound, and has important practical application value.

Contents of the invention

In order to solve the above problems, the present invention provides a method for preparing 1H-indazole derivatives shown in formula (I),

Wherein, R ₁ represents hydrogen, halogen atom, alkyl or haloalkyl;

The method comprises the steps of:

(1)

When R represents _an alkyl group or a haloalkyl group, the compound of the formula (A1) is used as a raw material to obtain the compound of the formula (B) through a nitration reaction;

When R represents _a halogen atom, the compound of formula (A2) is used as a raw material to obtain the compound of formula (B) through a halogenation reaction;

(2)

Using the compound of formula (B) as a raw material, a nitro group on the compound of formula (B) is reduced to obtain the compound of formula (C);

(3)

The compound of formula (C) is used as a raw material, nitrite is added, and the compound of formula (I) is obtained through diazotization and ring closure.

Further, the alkyl group is a C ₁ -C ₄ alkyl group, and the haloalkyl group is a C ₁ -C ₄ haloalkyl group.

Preferably, the C ₁ -C ₄ alkyl group is selected from methyl; the C ₁ -C ₄ haloalkyl group is selected from trifluoromethyl, difluoromethyl or monofluoromethyl.

Further, the halogen atom is chlorine atom, bromine atom or iodine atom.

Further, in step (1), the nitration reaction is carried out under the condition that any one of concentrated sulfuric acid, concentrated nitric acid or fuming nitric acid exists simultaneously with nitrate; preferably concentrated sulfuric acid;

The molar ratio of the nitrate to the compound of formula (A1) is 1.5-3.5:1.

Further, in step (1), the halogenation reagent of the halogenation reaction is selected from 1,3-dibromo-5,5-dimethylhydantoin, N-bromosuccinimide, trichloroiso Any of cyanuric acid or N-iodosuccinimide; preferably 1,3-dibromo-5,5-dimethylhydantoin;

The halogenation reaction is carried out in the presence of an acid; the acid is selected from any one of concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid or trifluoroacetic acid, preferably concentrated sulfuric acid.

Further, in step (2), the reduction reaction is carried out in the presence of iron and hydrochloric acid; preferably, the molar ratio of iron to the compound of formula (B) is 2 to 4:1;

The solvent of the reduction reaction is selected from any one of methanol, dioxane, ethanol or water or their mixed solvent, preferably a mixed solvent of methanol and dioxane;

The temperature of the reduction reaction is 20-80°C; preferably 80°C.

Further, in step (3), the nitrite is sodium nitrite; the solvent for the reaction is hydrochloric acid, sulfuric acid, acetic acid or formic acid, preferably acetic acid.

Further, the molar ratio of the nitrite to the compound of formula (C) is 1.5-3.5:1; the nitrite is added at a temperature of -5°C to 5°C.

The present invention also provides a method for preparing the compound of formula (II), characterized in that: comprising the following steps:

Wherein, R is as defined above _;

Using the compound of formula (I) as a raw material, the compound of formula (II) is obtained by reducing the nitro group to an amino group; the compound of formula (I) is prepared according to the aforementioned method.

Further, the reduction is carried out in the presence of iron and ammonium chloride.

In the present invention, the C ₁ -C ₄ alkyl group refers to a C ₁ , C ₂ , C ₃ , C ₄ alkyl group, that is, a straight-chain or branched-chain alkyl group with 1-4 carbon atoms, for example Methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, etc.

Compared with the existing method, the method of the invention can synthesize various 1H-indazole derivatives, has short synthesis route and high yield, and is more suitable for industrial production.

Apparently, according to the above content of the present invention, according to common technical knowledge and conventional means in this field, without departing from the above basic technical idea of the present invention, other various forms of modification, replacement or change can also be made.

The above-mentioned content of the present invention will be further described in detail below through specific implementation in the form of examples. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Detailed ways

PE: petroleum ether.

EA: ethyl acetate.

Dioxane: dioxane.

Example 1 Preparation of 6-bromo-4-nitro-1H-indazole (4)

1, Synthesis of 5-bromo-2 methyl-1,3-dinitrobenzene (2)

Take a dry 50mL pear-shaped bottle, add 2-methyl-1,3-dinitrobenzene (1) (CAS: 606-20-2, 5.00g, 27.45mmol, purchased from Chengdu Ruioke Reagent Company) was dissolved, and 1,3-dibromo-5,5-dimethylhydantoin (CAS: 77-48-5, 4.29g, 15.00mmol, purchased from Chengdu Ruioke Reagent Co., Ltd. ), the dropwise addition was completed, and the reaction was stirred at room temperature for 15 h. TLC showed that the reaction of the raw materials was complete. The reaction solution was slowly poured into ice water, filtered, and the filter cake was vacuum-dried to obtain a white solid powder (6.59 g, yield 92%).

The inventor screened the process, that is, according to the above method, the difference is that different halogenating reagents and acids are used, and the results are shown in Table 1 below.

Table 1

2, Synthesis of 5-bromo-2-methyl-3-nitroaniline (3)

Take a dry 50mL pear-shaped flask, dissolve 5-bromo-2methyl-1,3-dinitrobenzene (2) (5.00g, 19.16mmol) with 20mL methanol and 10mL dioxane, and stir at room temperature Slowly add 16.48mL of concentrated hydrochloric acid and iron powder (3.22g, 57.47mmol). After the addition is complete, raise the temperature to 80°C and stir and reflux for 12h. TLC shows that the reaction of the raw materials is basically complete. =5:1) Purification gave light yellow solid powder (2.74g, yield 62%).

According to the above method, the difference is that different iron powder additions, acids, solvents, and reaction temperatures are used. The results are shown in Table 2 below.

Table 2

3. Synthesis of 6-bromo-4nitro-1H-indazole (4)

Take a dry 25mL pear-shaped bottle, dissolve 5-bromo-2-methyl-3-nitroaniline (3) (0.40g, 1.73mmol) in 7mL of glacial acetic acid, and dissolve 2mL of sodium nitrite under mechanical stirring at 0°C (0.24g, 3.46mmol) solution was slowly added dropwise to the reaction solution, after the addition was completed, it was raised to room temperature and stirred for 12 hours. TLC showed that the raw materials were completely reacted, and the reaction solution was diluted with water, and solids were precipitated, filtered, and the filter cake was vacuum-dried. Purified by column chromatography (PE:EA=5:1) to obtain a yellow solid powder (0.40 g, yield 96%).

Structural identification: Compared with the reference substance CAS: 885518-46-7 (purchased from Jiangsu Nantong Biotechnology Co., Ltd.) with the same structure, the HPLC pattern is completely consistent. The purity is 98% by HPLC; ¹ H-NMR (400MHz, d6-DMSO, ppm): δ12.46 (br, 1H), 8.30 (s, 1H), 8.20 (s, 1H), 8.12 (s, 1H ),4.60(br,2H).

The inventor screened the process, that is, according to the above method, the difference is that different nitrite additions, acids, and feed temperatures are used, and the results are shown in Table 3 below.

table 3

Example 2 Preparation of 3, 6-methyl-4-nitro-1H-indazole (8)

1. Synthesis of 2,5-dimethyl-1,3-dinitrobenzene (6)

Take a dry 50mL pear-shaped flask, dissolve xylene (5) (2.00mL, 16.23mmol) with 20mL of concentrated sulfuric acid, slowly add potassium nitrate (4.91g, 48.68mmol) under stirring at room temperature, after the addition is complete, stir at room temperature for 2 hours, TLC showed that the reaction of the raw materials was complete, the reaction solution was slowly poured into ice water, filtered, the filter cake was vacuum-dried, and purified by column chromatography (PE:EA=80:1) to obtain a light yellow solid (6) (1.62g, yield 51%).

Structural identification: ¹ H-NMR (400MHz, CDCl ₃ , ppm): δ13.0 (br, 1H, NH), 7.42 (s, 2H, Ar-H), 2.45 (s, 6H, CH3).ESI-MS :197.05[M+H].

The inventor screened the process, that is, according to the above method, the difference is that different acids are used, and the results are shown in Table 4 below.

Table 4

2. Synthesis of 2,5-dimethyl-3-nitroaniline (7)

According to the method for preparing 5-bromo-2-methyl-3-nitroaniline (3) in Example 1, 2,5-dimethyl-3-nitroaniline (7) was prepared, yellow solid, yield 65%.

3. Synthesis of 6-methyl-4-nitro-1H-indazole (8)

According to the method for preparing 6-bromo-4-nitro-1H-indazole (4) in Example 1, the synthesis of 6-methyl-4-nitro-1H-indazole (8) was prepared, yellow solid, yield 52%.

The purity is 98% by HPLC; structural identification: ¹ H-NMR (400MHz,d ₆ -DMSO,ppm): δ12.46(br,1H),8.20(s,1H),8.10(s,1H),7.87 (s,1H),2.35(s,3H).ESI-MS:178.18[M+H].

Example 3 Preparation of 6-trifluoromethyl-4-nitro-1H-indazole (12)

1, Synthesis of 2-methyl-5-trifluoromethyl-1,3-dinitrobenzene (10)

Using 4-trifluoromethyl-toluene (9) (CAS: 6140-17-6, purchased from Chengdu Ruioke Reagent Co., Ltd.) - The method of dinitrobenzene (6), prepared to obtain 2-methyl-5-trifluoromethyl-1,3-dinitrobenzene (10), a yellow solid, with a yield of 75%.

Structural identification: ¹ H-NMR (400MHz, CDCl ₃ , ppm): δ13.0 (br, 1H, NH), 8.29 (s, 2H, Ar-H), 2.69 (s, 3H, CH3).ESI-MS :251.02[M+H].

2, Synthesis of 2-methyl-5-trifluoromethyl-3-nitroaniline (11)

According to the method for preparing 5-bromo-2-methyl-3-nitroaniline (3) in Example 1, 2-methyl-5-trifluoromethyl-3-nitroaniline (11) was prepared, yellow Solid, yield 68%.

3. Synthesis of 6-trifluoromethyl-4-nitro-1H-indazole (12)

According to the method for preparing 6-bromo-4nitro-1H-indazole (4) in Example 1, 6-trifluoromethyl-4nitro-1H-indazole (12) was prepared with a yield of 79%. The purity was 98% by HPLC. Structural identification: ¹ H-NMR (400MHz,d ₆ -DMSO,ppm): δ12.46(br,1H),8.20(s,1H),8.12(s,1H),7.80(s,1H).ESI- MS:232.13[M+H].

Embodiment 4 Preparation of the compound of formula (II) of the present invention

Dissolve the nitro compound (8.26mmol) in a mixed solvent of ethanol (20mL) and water (10mL), add ammonium chloride (221.5mg, 4.13mmol), and first add a part of iron powder (1.3g, 23.46mmol) , the temperature was raised to 80° C. and the reaction was stirred for 5 minutes, then the remaining iron powder (1.0 g, 17.86 mmol) was added, and the reaction was continued to stir for 20 minutes. After the reaction of the raw materials was detected by TLC, the reaction solution was filtered while it was hot, and the filter residue was washed with ethanol (10 mL). Ethanol was spun off under reduced pressure, and the aqueous layer was extracted three times with ethyl acetate (20 mL). The organic phases were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, spin-dried, and passed through a column (PE:EA=8:1) to obtain the corresponding amino compound.

1. 6-Bromo-1H-indazol-4-amine (14)

Yellow solid, yield 92%. The purity is 98% by HPLC; ¹ H-NMR (400MHz, d ₆ -DMSO, ppm): δ12.46 (br, 1H), 8.15 (s, 1H), 7.56 (s, 1H), 6.88 (s, 1H),5.80(br,2H).ESI-MS:213.05[M+H].

2. 6-Methyl-1H-indazol-4-amine (15)

Yellow solid, yield 75%. The purity is 98% by HPLC; ¹ H-NMR (400MHz, d ₆ -DMSO, ppm): δ12.46 (br, 1H), 7.70 (s, 1H), 7.16 (s, 1H), 6.85 (s, 1H), 4.60(br,2H), 2.21(s,3H). ESI-MS: 148.10[M+H].

3. 6-trifluoromethyl-1H-indazol-4-amine (16)

Yellow solid, yield 95%. The purity is 98% by HPLC; ¹ H-NMR (400MHz, CDCl ₃ , ppm): δ13.0 (br, 1H, NH), 8.10 (s, 1H, indazole-H), 7.21 (s, 1H, indazole -H),6.58(s,1H,indazole-H),4.37(br,2H,NH2).ESI-MS:202.05[M+H].

4. 1H-Indazol-4-amine (17)

Yellow solid, yield 96%. The purity is 98% by HPLC; ¹ H-NMR (400MHz, CDCl ₃ , ppm): δ13.0 (br, 1H, NH), 8.10 (s, 1H, indazole-H), 7.60 (d, 1H, J =6.4Hz, indazole-H), 7.20(m, 1H, indazole-H), 6.48(d, 1H, J=6.4Hz, indazole-H), 4.37(br, 2H, NH2).ESI-MS: 134.05 [M+H].

Experimental example The inhibitory activity of compound of the present invention to IDO protein

Recombinant human IDO protein is expressed in Escherichia coli and purified by nickel affinity chromatography. The compound's IDO inhibitory activity test uses L-tryptophan as a substrate. The compounds to be tested were dissolved in 10% DMSO solution to prepare dilutions. Take 5uL of the diluted solution and add it to the 100μL reaction system. The 100 μL reaction system contained 0.5% DMSO, 40 nmol/L IDO, 900 μmol/LL-tryptophan, and other reaction coexistents (potassium phosphate buffer, ascorbic acid, catalase, methylene blue). The reaction mixture was incubated at 37°C for 180 minutes, and then trichloroacetic acid was added to terminate the reaction. The concentration of N-formylkynurenine produced was measured at 321 nm using a Tecan Infinite M1000 microplate reader to evaluate the inhibitory activity of the compound on IDO. The negative control was 5 μL of buffer instead of IDO. The Phase III IDO inhibitor INCB024360 was used as a positive control to verify the effectiveness of the IDO activity detection system established in this experiment.

Three replicate wells were set up for each concentration. Data analysis was performed using the software Graphpad Prism. Absorbance (A _t ) was defined as 100% activity in a reaction solution containing no test compound. Absorbance (A _b ) was defined as 0% activity in a reaction solution without IDO. For the test compound, the formula for calculating the activity is: %activity=[(AA _b )/(A _t -A _b )]×100, where A is the absorbance of the reaction solution containing the test compound. The formula for calculating the inhibition rate is: %inhibition=100-%activity.

Through the above experimental method, the inhibitory activity of the compound prepared in the present invention against IDO was tested. The inhibitory activities of specific compounds at concentrations of 1 μM, 10 μM and 100 μM are shown in Table 5.

Wherein A indicates that the inhibition rate is greater than 90%, B indicates that the inhibition rate is 70-90%, C indicates that the inhibition rate is 50-69%; D indicates that the inhibition rate is 10-49%, E indicates that the inhibition rate is less than 10%; positive control The inhibition rate was 46% at a concentration of 0.05 μM.

Table 5 The inhibitory activity of compounds of the present invention to IDO

Tests have proved that the 1H-indazole compounds prepared by the method of the present invention have a significant inhibitory effect on IDO, and can be used to prevent and/or treat various diseases, such as Alzheimer's disease, cataract, and cellular immune activation-related diseases. Infection, autoimmune disease, AIDS, cancer, depression, or abnormal tryptophan metabolism, etc.

Claims (10)

1. a kind of method of formula (I) compound,

Wherein, R₁Represent hydrogen, halogen atom, alkyl or haloalkyl；

It the described method comprises the following steps：

Work as R₁When representing alkyl or haloalkyl, using formula (A1) compound as raw material, formula (B) compound is obtained through nitration reaction；

Work as R₁When representing halogen atom, using formula (A2) compound as raw material, formula (B) compound is obtained through halogenating reaction；

Using formula (B) compound as raw material, by a nitro in formula (B) compound through reduction reaction, formula (C) compound is obtained；

Using formula (C) compound as raw material, nitrite is added, formula (I) compound is obtained through diazotising, ring-closure reaction.

2. according to the method for claim 1, it is characterised in that：The alkyl is C₁~C₄Alkyl, the haloalkyl is C₁~C₄Haloalkyl；

Preferably, the C₁~C₄Alkyl be selected from methyl；The C₁~C₄Haloalkyl be selected from trifluoromethyl, difluoromethyl or One methyl fluoride.

3. according to the method for claim 1, it is characterised in that：The halogen atom is chlorine atom, bromine atoms or iodine atom.

4. according to the method described in claim any one of 1-3, it is characterised in that：In step (1), the nitration reaction is dense Any of sulfuric acid, concentrated nitric acid or fuming nitric aicd are carried out with nitrate under the conditions of simultaneous；It is preferred that the concentrated sulfuric acid；

The mol ratio of the nitrate and formula (A1) compound is 1.5~3.5：1.

5. according to the method for claim 4, it is characterised in that：In step (1), the halogenating agent of the halogenating reaction is selected from It is any in 1,3- bis- bromo- 5,5- DMHs, N- bromo-succinimides, sym-closene or N- N-iodosuccinimides Kind；It is preferred that 1,3- bis- bromo- 5,5- DMHs；

The halogenating reaction is carried out in the presence of acid；The acid is in the concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid or trifluoroacetic acid Any, preferred concentrated sulfuric acid.

6. according to the method described in claim any one of 1-3, it is characterised in that：In step (2), the reduction reaction is in iron With carry out in the presence of hydrochloric acid；Preferably, the mol ratio of iron and formula (B) compound is 2~4:1；

The solvent of the reduction reaction is selected from any of methanol, dioxane, ethanol or water or their mixed solvent, excellent Select the mixed solvent of methanol and dioxane；

The temperature of the reduction reaction is 20-80 DEG C；It is preferred that 80 DEG C.

7. according to the method described in claim any one of 1-3, it is characterised in that：In step (3), the nitrite is nitrous Sour sodium；The solvent of the reaction is hydrochloric acid, sulfuric acid, preferably acid or glacial acetic acid, acetic acid.

8. the method according to claim 6 or 7, it is characterised in that：The mol ratio of the nitrite and formula (C) chemical combination is 1.5~3.5：1；The nitrite adds at a temperature of -5 DEG C~5 DEG C.

A kind of 9. method of formula (II) compound, it is characterised in that：Comprise the following steps：

Wherein, R₁As any one of claim 1-4 is defined；

Using formula (I) compound as raw material, formula (II) compound is obtained by what nitro was reduced to amino；Formula (I) compound is It is prepared according to the method described in claim any one of 1-8.

10. according to the method for claim 9, it is characterised in that：The reduction is carried out in the presence of iron and ammonium chloride.