LITHIUM TETRAFLUOROBORATE-ASSISTED REACTIONS OF N-(ALPHA-AMINOALKYL)BENZOTRIAZOLES WITH OLEFINS AND 1,3-DIENES - NEW SYNTHESES OF 1,2,5,6-TETRAHYDROPYRIDINIUM SALTS, 1,2,3,4-TETRAHYDROQUINOLINES, AND SOME RELATED HETEROCYCLIC-SYSTEMS

Lithium tetrafluoroborate efficiently assists the ionization of N-(alp ha-aminoalkyl)benzotriazoles in tetrahydrofuran solution to generate r eactive iminium intermediates, which can be trapped with electron-rich olefins and with 1,3-dienes. Hetero Diels-Alder cycloadditions of N-( alpha-dialkylami-noalkyl)benzotriazoles and lithium tetrafluoroborate with 1,3-dienes thus gave 1,2,5,6-tetrahydropyridinium salts, while re actions of N-[alpha-(arylamino)alkyl]benzotriazoles with olefins and 1 ,3-dienes afforded substituted 1,2,3,4-tetrahydroquinolines, as well a s examples of the new heterocyclic systems indeno[2,1-c]quinoline and pyrido[3,2,1-kl]-1,4-phenothiazine.