Addition of benzotriazole to vinyl ethers. Chemistry of the adducts

Abstract

Benzotriazole adds readily to ethyl vinyl ether, to 2,3-dihydrofuran, and to 3,4-dihydro-2H-pyran to form the respective α-benzotriazolyl ethers. Reactions of benzotriazole with α-methoxy derivatives of tetrahydrofuran and tetrahydropyran give similar products by substitution of benzotriazolyl for the methoxy groups. The corresponding adducts of benzotriazole and vinyl acetates are unstable and eliminate acetate anion to form geminal bis(benzotriazolyl)alkanes. The products show benzotriazol-1-yl to -2-yl isomerization. α-Benzotriazolyl derivatives of tetrahydrofuran and tetrahydropyran react with phenyl- and alkynyl-magnesium reagents to give the respective α-phenyl or α-alkynyl cycloethers. Alkylmagnesium halides by contrast attack the benzotriazolyl N-3 atom of these adducts and open the tetrahydropyranyl ring with formation of an N,N′-disubstituted o-phenylenediamine. ¹H and ¹³C NMR spectra of the products are discussed.