On the Baylis–Hillman reaction of acrylate, acrylonitrile, and acrolein with some non-enolizable α-dicarbonyl compounds: synthesis of phytotoxic bipolaroxin models

Abstract

The Baylis–Hillman reaction of acrylonitrile, methyl acrylate, and acrolein with several cyclic α-dicarbonyl compounds was investigated. Whereas acrylonitrile reacted with most of these ketones, giving good yields of the expected 1′-cyanovinyl carbinols, the more sterically demanding methyl acrylate failed to undergo the reaction. Attempted Baylis–Hillman reaction of acrolein with the 1,2-dicarbonyl substrates usually resulted in polymers but, in two cases, the desired α-substituted acroleins were obtained. An alternative route to such compounds was developed, employing a Grignard – allylic oxidation sequence. In bioassays, some of the products, embodying the functionality believed responsible for the phytotoxicity of the sesquiterpene bipolaroxin, inhibited germination of lettuce seeds. This activity diminished with time. Keywords: Baylis–Hillman, acrylonitrile, acrylate, acrolein, α-dicarbonyl, bipolaroxin, phytotoxicity.