PREPARATION OF DONOR-ACCEPTOR-SUBSTITUTED VINYLCYCLOBUTANES

2‐Methylen‐1,3‐dioxolane (1) and the methyl acrylates or crotonates 2 form [2+2] cycloadducts 3 which are reduced to give alcohols 6. Oxidation of these alcohols at low temperatures leads to unstable aldehydes 7, which either rearrange to dihydropyrans 5 or react with Wittig(‐Horner) reagents to afford donor‐acceptor‐substituted vinylcyclobutanes 8. The cis‐vinylcyclobutane 8g is prepared by [2+2] cycloaddition of dioxolane 1 and methyl (2E,4Z)‐hexadienoate (9). The configurations and preferred conformations of the vinylcyclobutanes 8 have unequivocally been assigned on the basis of 13C‐and 1H‐NMR spectra. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim