Patent ID: 7528264

Claim:
A process for preparing a quinolone intermediate having the formula: wherein: n is 1 or 2; X is selected from the group consisting of C 1 -C 4 alkyl, C 6 -C 10 aryl or alkylaryl, and C 3 -C 6 cycloalkyl; and Z is selected from the group consisting of CO 2 X and COX, wherein X is as defined above; said process comprising the steps of: (a) reacting the compound of Formula (II): wherein Y is selected from the group consisting of C 1 -C 4 alkyl, C 6 -C 10 aryl or alkylaryl, and C 3 -C 6 cycloalkyl; and X, and Z are as defined for Formula (I); with about 2 to about 4 equivalents of sodium borohydride in alkanol or an admixture of alkanol/ether in a v/v ratio of from about 100/0 to about 20/80, at about −20° C. to about 10° C.; (b) setting the temperature of the reaction mixture to a temperature in the range from about 5° C. to about 15° C.; and (c) adding about 1.5 to about 3.0 equivalents of a calcium salt.