An unusual doubly substituted product from the phase-transfer-catalyzed Heck reactions of o-bromobenzaldehydes with methyl acrylate
摘要:
The reactions of o-bromobenzaldehydes with methyl acrylate under Heck conditions and with phase-transfer catalysis to yield significant amounts of doubly substituted deformylated products 1A-E in addition to the expected o-formyl cinnamates 2A-E are reported. X-ray crystallography of one such product (4) established that the bromine was replaced by a propionate and the formyl group by an acrylate residue. Employment of deuterium-labeled substrates showed that the hydrogen atom of the formyl group of the substrate was transferred intramolecularly and regiospecifically to the benzylic carbon of the propionate substituent of the product. A tentative hypothesis is advanced to explain these and other experimental findings.