OXYGENATED DIENES AND SYNTHESIS OF METHYLENEDIOXYBIPHENYL DERIVATIVES

New dienoate and trienoate esters 5, 8, 9 and 10 are described. Their preparation by the two standard variants of the Wittig reaction led to an uncommon reversal of utility in that the phosphorane procedure proved much superior to the phosphonate anion procedure. Reactivities of the new dienoate esters 8 and 10 and of the related diene aldehyde derivatives 3 and 4 toward several dienophiles were explored. Through the halolactonization reaction, selective protection of one carboxyl function in a tetrahydrophthalic acid derivative was achieved, allowing esterification of the other and removal of the first in an oxidative decarboxylation. The oxidative decarboxylation was brought about by 2,3-dichloro-5,6-dicyanobenzoquinone, a novel reaction for quinones. The combination of these reactions allowed selective syntheses of 2- and 3-piperonylbenzoic acids (17 and 19) and their ethyl esters (18 and 20) and of the parent 3,4-methylenedioxybiphenyl (16), Aspects of the NMR spectra of a number of these compounds are discussed, as they shed light on the rigid conformation expected for bridged halolactones. © 1969.