REGIOCHEMICAL CONTROL OF THE RING-OPENING OF AZIRIDINES BY MEANS OF CHELATING PROCESSES .2. SYNTHESIS AND RING-OPENING REACTIONS OF AZIRIDINES DERIVED FROM 5,6-DIHYDRO-2H-PYRAN AND OF THE DIASTEREOISOMERIC CIS-AZIRIDINE AND TRANS-AZIRIDINE DERIVED FROM 3-(BENZYLOXY)CYCLOHEXENE, 2-(BENZYLOXY)3,6-DIHYDRO-2H-PYRAN, AND 2-(BENZYLOXY)-6-METHYL-3,6-DIHYDRO-2H-PYRAN

The regiochemical outcome of the ring opening of the activated and una ctivated title aziridines was examined, in some cases a nice degree of regiocontrol can be obtained depending on the opening reaction condit ions (standard, metal-assisted, or under acid-proton catalysis). The r esults have been rationalized by admitting the incursion, under approp riate reaction conditions, of chelated bidentate structures in which t he metal or, in some cases, the proton is coordinated between the azir idine nitrogen and the O-heterofunctionality. (C) 1997, Elsevier Scien ce Ltd.