Ashraf A. A. Abdel-Fattah

Stereochemical aspects of novel 5,6-dihydro-4H-1,3-oxazines

Novel polysubstituted 5,6-dihydro-4H-1,3-oxazines are synthesized by 1,4-cycloaddition of unactivated olefins with N-acyliminiums from benzotriazole precursors. The configuration and conformation of the products are deduced from NMR investigation. The regio- and exo–endo stereochemistry of the cycloaddition are discussed. Conformations of compounds of six types of substitution (6-mono; 6,6-, 5,6- and 4,6-di; 4,6,6- and 4,5,6-tri) are rationalized on the basis of axial-1,3-repulsion and the anomeric effect.

Novel Synthesis of α-Benzotriazolyl-substituted Ketones†

Silyl enol ethers react with 1-chlorobenzotriazole to provide a new general method for the preparation of α-benzotriazolyl-substituted ketones.