Synthesis of b-Arylpropanoates and Cinnamaldehydes

Significance

Palladacycle 1 derived from Kaiser oxime resin catalyzed the chemoselective Heck reaction of acrolein diethyl acetal with aryl halides. Thus, the reaction of acrolein diethyl acetal with aryl halides in the presence of catalyst 1, (dicyclohexyl)methylamine, and TBAB, followed by acid hydrolysis gave the corresponding ethyl 3-arylpropanoates 2 in 61-92 yield (eq. 1). In contrast, the reaction with catalyst 1, K₂CO₃, TBAA, and KCl afforded the corresponding cinnamaldehydes 3 in 46-99% yield (eq. 2). In the synthesis of ethyl 3-(4-cyanophenyl)propanoate, the catalyst was recovered by filtration and reused four times (1^st reuse: 88% yield; 2^nd reuse: 91% yield; 3^rd reuse: 86% yield; 4^th reuse: 65% yield).