Ene Reactions of 2-Phosphonoacrylates

Abstract

Trimethyl 2-phosphonoacrylate (la) undergoes EtAlCl2-catalyzed ene reactions in high yield at 0 °C with most classes of alkenes. The products are useful reagents for the phosphonate modification of the Wittig reaction. EtAlCl2-catalyzed ene reaction of la with 6-methyl-5-hepten-2-one (18) at -78 °C gives 19, which undergoes an intramolecular Wittig reaction to give 21. Ethyl α-methylene-1-cyclohexenebutanoate (16) undergoes a Lewis acid initiated cyclization to give the cyclopropane 30 and octalins 31 and 32. © 1983, American Chemical Society. All rights reserved.