Processes for producing racemic piperidine derivative and for producing optically active piperidine derivative
Disclosed are a method for producing racemic piperidine derivatives by processing optically-active piperidine derivatives in a hydrogen atmosphere in the presence of a reducing catalyst; and a method for producing optically-active piperidine derivatives or their acid salts by optically resolving the racemic piperidine derivatives obtained in the former method.
1. A method for producing racemic piperidine derivatives, which comprises processing an optically-active piperidine derivative of any of general formulae (1), (2) and (3):
wherein R 1 represents a lower alkyl group having from 1 to 4 carbon atoms, a phenyl group, or an aralkyl group; R 2 , R 3 and R 4 may be the same or different, each representing a hydrogen atom, an alkyl group, a phenyl group, an aralkyl group, an alkoxycarbonyl group, an alkylsulfonyl group, an allylsulfonyl group, an aralkylsulfonyl group, or an acyl group; R 5 represents an alkyl group, a phenyl group, an aralkyl group, an alkoxycarbonyl group, an alkylsulfonyl group, an allylsulfonyl group, an aralkylsulfonyl group, or an acyl group, in a hydrogen atmosphere in the presence of a reducing catalyst.
2. The method for producing racemic piperidine derivatives as claimed in claim 1 , wherein the reducing catalyst contains a metal of Group VIII of the Periodic Table.
3. The method for producing racemic piperidine derivatives as claimed in claim 2 , wherein the metal of Group VIII of the Periodic Table is platinum.
4. The method for producing racemic piperidine derivatives as claimed in any one of claims 1 to 3 , wherein the hydrogen atmosphere is a pressure system of at least 0.2 MPa.
5. The method for producing racemic piperidine derivatives as claimed in claim 1 , wherein the optically-active piperidine derivative is one represented by a formula (4) or (5):
wherein R 1 represents a lower alkyl group having from 1 to 4 carbon atoms; and R 4 represents an alkylsulfonyl group having from 1 to 4 carbon atoms.
6. The method for producing racemic piperidine derivatives as claimed in claim 1 , wherein the optically-active piperidine derivative is optically-active 3-[3-(methylsulfonyl)phenyl]-1-propylpiperidine of a formula (6):