JPS62212371A - Selective hydrogenation method for isoquinolines - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for selective hydrogenation of isoquinolines.

Isoquinolines are contained in large amounts in coal and are used in agricultural chemicals, medicines,
They are intermediates for dyes and surfactants, and 1,2,3,4-tetrahydroisoquinolines whose nitrogen-containing rings are hydrogenated are particularly important intermediates.

Hitherto, known methods for hydrogenating isoquinolines include, for example, a method using tin and hydrochloric acid, a method using sodium and ethanol, and a method using a nickel catalyst, but all of these methods require complicated operations. There were problems such as high yield and low yield, and it could not be said to be an industrially advantageous method.

Therefore, the present inventors investigated a method for solving this problem and easily and selectively hydrogenating the nitrogen-containing rings of isoquinolines in a good yield. We have now discovered that the nitrogen-containing rings of isoquinolines are selectively hydrogenated under water gas shift conditions, leading to the present invention.

That is, the present invention provides isoquinolines represented by the general formula (wherein R1 and R2 represent a hydrogen atom, an alkyl group, an alkoxyl group, or a benzyloxy group, and R3 represents a hydrogen atom or an alkyl group),
- Provides a method for selective hydrogenation of isoquinolines, which is characterized by selectively reducing nitrogen-containing rings using a Rh--Co catalyst in the presence of carbon oxide and water.

The Rh-Co catalyst used in the present invention is usually R
h, 1(Co), n and m are not particularly limited, and conventionally known ones are used, but typically Rh
b(Co)+b is mentioned.

The amount of the catalyst to be used is usually 0.001 to 0.2 times the mole of the raw material isoquinoline, preferably 0.005 to 0.
．． The amount is 1 mole, more preferably 0.005 to 0.05 mole.

The catalyst used in this reaction can be recovered from the reaction solution and reused after the reaction is completed.

In this reaction, water is 2
More than twice the equivalent amount is used, and this may be used in large excess to also serve as a solvent.

The reaction is usually carried out under pressure of carbon oxide, and the carbon monoxide pressure in the reaction system is usually in the range of 10 to 100 kg/-. Of course, the reaction proceeds even under normal pressure, but the reaction t
It takes an extremely long time to complete.

The reaction is usually carried out in the presence of a solvent, which includes water, aliphatic or alicyclic alcohols, alkoxy alcohols, ethers, etc., and is particularly limited as long as it is not an unsaturated compound active in the reaction. Alcohols, alkoxy alcohols, and ethers are preferably used, although they are not.

The amount of solvent used is usually 1 to 5% based on the raw material isoquinoline.
0 times the weight.

The reaction temperature depends on the type of raw material isoquinoline, the solvent used, -
Although it varies depending on the oxidation carbon pressure, etc., it is usually 100 to 20
It is 0°C.

Thus, according to the method of the present invention, nitrogen-containing rings are selectively hydrogenated, but in this method, carbon monoxide is inserted between NH bonds after hydrogenation, and N-formyl-1,2, 3,
4-tetrahydroisoquinoline is obtained.

This formylated product can be easily deformylated and converted to 1,2,3,4-tetrahydroisoquinoline by treatment with concentrated hydrochloric acid and methanol or caustic soda and methanol, for example.

Furthermore, even in the case of isoquinolines having a benzyloxy group which is easily hydrogenolyzed by ordinary catalytic hydrogenation, hydrogenolysis does not occur in the method of the present invention.

The present invention will be explained below with reference to Examples.

Example 1 Isoquinoline 2.3 in an autoclave with a capacity of 1ON1
Xl0-3 mol, Rh & (CO)+b O,019
X10-3 mol, water 28X10-" mol and 2-methoxyethanol 2- were charged, and -56 kg/carbon oxide was added.
After pressurizing cd-G, it was heated to 150°C.

After 24 hours, the mixture was cooled, the catalyst was removed, and N-formyl-1,2,3,4-tetrahydroisoquinoline was obtained in a yield of 69% by distillation.

Example 2 N-formyl-6-pendyloxy7-methoxyisoquinoline was obtained in a yield of 66% by the same reaction and post-treatment as in Example 1 except that 6-pendyloxy7-methoxyisoquinoline was used instead of isoquinoline. Ta·

Claims (1)

[Claims] General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R_1 and R_2 are hydrogen atoms, alkyl groups,
The nitrogen-containing ring of an isoquinoline represented by an alkoxyl group or a benzyloxy group and R_3 represents a hydrogen atom or an alkyl group is selectively reduced using a Rh-CO catalyst in the presence of carbon monoxide and water. A method for selective hydrogenation of isoquinolines, characterized by the following.