KNOEVENAGEL CONDENSATION OF 3,5-DIMETHOXY PHENYLACETALDEHYDE WITH ETHYL HYDROGEN MALONATE

Knoevenagel condensation of 3,5-dimethoxyphenylacetaldehyde with ethyl hydrogen malonate in pyridine-piperidine led to the isolation of two products, One is not the expected 4-(3,5-dimethoxyphenyl)-2-butenoate, but is its isomeric 5-butenoate which could not be equilibrated with its 2-isomer by a base like its parent 4-phenyl-2- and -3-butenoates, The other is 2',4',2 '',4 -2,3:6,7-dibenzo-9-oxabicyclo[3.3.1]nona-2,6 -diene which is formed by phenol-aldehyde condensation under the basic condition rather than usual dimerization brought about by Lewis acid catalysis.