Condensation of diethyl 2,4,6-Trioxoheptanedioate with 2-(Aryliminomethyl)phenols. A new synthesis of chromeno[4,3- b]pyridines.

Condensation of diethyl 2,4,6-trioxoheptanedioate with 4-methoxy-2-(4-methylphenyliminomethyl)-phenol in acetone gave diethyl 5-hydroxy-9-methoxy-1-(4-methylphenyl)-4-oxo-1,4a,5,10b-tetrahydro-4 Hchromeno[ 4,3- b]pyridine-2,5-dicarboxylate as a mixture of diastereoisomers. The major (4a R,5 R,10a R)-isomer was isolated as individual substance, and its structure was proved by X-ray analysis. [ABSTRACT FROM AUTHOR]