SYNTHESIS OF 2-ALKOXY SUBSTITUTED OLIGO AND POLY(1,4-PHENYLENEETHYLENE)S AND 2-ARYLBENZO[B]FURANES BY APPLYING THE SIEGRIST REACTION

Alkylation of 2-hydroxy-4-methylbenzaldehyde (1) yields the 2-alkoxy-4-methylbenzaldehydes (2a-1) which can be easily transformed to the Schiff bases 3a-1. The intermolecular self-condensation in a strongly alkaline medium leads to the oligo- and poly(1,4-phenyleneethenylene)s (4a-i) with an outstanding regular constitution and overall (E)-configuration. The terminal N-arylamino group can be cleaved by hydrolysis generating the compounds 5a-i. An intramolecular condensation forming the benzo[b]furanes 6j,k is observed for 3j,k - due to the activated OCH2 group in 2-position. Finally, both the 4-CH3 as well as the 2-OCH2 group take part in the reaction of 31. The twofold Schiff base 3m. obtained from 1 via 2m, yields the ladder polymer 7m.