Face Selectivity of the Diels-Alder Additions and Cheletropic Additions of Sulfur-Dioxide to 2-Vinyl-7-Oxabicyclo[2.2.1]Hept-2-Ene Derivatives
Racemic 6-ethenyl-7-oxabicyclo[2.2.l]hept-5-en-2-one (23), 5-ethenyl-7-oxabicyclo[2.2.1]hept-5-en-2-one (25) and their ethylene acetals 24 and 26, respectively, were derived from the Diels-Alder adduct of furan to 1-cyanovinyl acetate (27). The Diels-Alder additions of 26 to dimethyl acetylenedicarboxylate, to methyl propynoate, to N-phenylmaleimide, and to methyl acrylate were highly exo-face selective, as were the cycloadditions of methyl propynoate to dienones 23 and 25 and of dimethyl acetylenedicarboxylate to ethylenedioxy-diene 24. The cheletropic additions of SO2 to 23-26 gave exclusively the corresponding sulfolenes 57-60 resulting from the exo-face attack of the semicyclic dienes under conditions of kinetic and thermodynamic control.
Keywords: Non-conjugated chromophores ; double-bond deformation ; electronic ; control ; cyclo-additions ; stereochemical course ; cyclopentadiene rings ; organic electrophiles ; bicyclic frameworks ; organotin reagents ; coupling-constants
Univ lausanne,chim sect,ch-1005 lausanne,switzerland.
Record created on 2005-11-09, modified on 2016-08-08