Photochemical and thermal addition of alcohols to 2-cyanofuran. 1-alkoxy-2-cyanocyclopropane-3-carboxaldehydes; 2-alkoxy-3-cyano-2, 3-dihydrofuran; 1-alkoxy-1-(2-furan)-methylenimine; photochemical ring contraction; cis-trans-isomerization of dihydrofurans

Abstract

The photolysis of 2-cyanofuran in alcohols yields 1-alkoxy-2-cyanocyclopropane-3-carboxaldehydes as the major products, which rearrange thermally to trans-2-alkoxy-3-cyano-2,3-dihydrofurans and small amounts of cis-isomers. Thermal mutual rearrangements between trans- and cis-2- alkoxy-3-cyano-2, 3-dihydrofurans were studied. Liquid phase thermal addition of alcohols in a temperature range between 100° and 200° yields 1-alkoxy-1-(2-furan)-methylenimines, which rearrange photochemically to 2-furyl-methylamino-ketone in case of the methoxy derivative. 3-Cyano-furan does not yield photoaddition or thermal addition products. The different behaviors of 2- and 3-substituted furans are discussed. © 1973.