Patent ID: 7576214
Filing Date: 2009-08-18
Classification: C07D

Abstract:
1. A process for preparing 1,8-naphthyridine-3-carboxylic acid compound of the following formula (5) in which Y represents straight-chain, branched or cyclic alkyl, having 1 to 5 carbon atoms, and unsubstituted or substituted by halogen, said process comprising: the first step a) the compound of the following formula (1), is reacted with dimethylformamide dialkylacetal of formula Me 2 NCH(OR) 2 (wherein R represents straight-chain, branched or cyclic alkyl having 1 to 9 carbon atoms, or represents benzyl) in a solvent in the presence of acid catalyst to prepare the compound of the following formula (2), the second step b) the resulting reaction mixture of the following formula (2), is reacted with amine of formula YNH in which Y is defined as above, the third step c) the resulting compound of the following formula (3), in which Y is as defined above, is cyclized in the presence of quaternary ammonium salt and a base to prepare 1,8-naphthyridine-3-carboxylic acid ester of the following formula (4), in which Y is as defined above, and in the fourth step d) the resulting compound of the following formula (4), in which Y is as defined above, is hydrolyzed in the presence of an acid to prepare 1,8-naphthyridine-3-carboxylic acid compound of the said formula (5), said process is characterized by a one pot operation of the above steps using a single solvent system without intermediate isolation.