Visible light-promoted synthesis of 4,6a-dihydropyrrolo[3,4-c]pyrrole-1,3(2H,3aH)-diones via [3+2] cycloaddition reaction of 2H-azirines with maleimides
Stereoselectivity of Cydoaddition of<i>N</i>-(Cyanomethyl)- and<i>N</i>-(α-Cyanobenzyl)imines with Olefinic Dipolarophiles. Synthetic Equivalents of Nitrile Ylide 1,3-Dipoles
N-(Cyanomethyl)- and N-(α-cyanobenzyl)imines derived from a variety of aldehydes and ketones can tautomerize into N-protonated azomethine ylides which undergo cycloadditions with olefinic dipolarophiles. These cycloadditions are often accompanied by the elimination of HCN, mostly in a stereospecific manner, showing these imines to be synthetic equivalents of nonstabilized nitrile ylides. Stereoselectivity
The Synthesis of Pyrroles and Dihydropyrroles by 1,3-Dipolar Cyclisations of<i>N</i>-Arylmethylene[(benzotriazol-1-yl)arylmethyl]amines
作者:Alan R. Katritzky、Gregory J. Hitchings、Xiaohong Zhao
DOI:10.1055/s-1991-26595
日期:——
N-Arylmethylene[(benzotriazol-1-yl)arylmethyl]amines 1 are prepared by the reaction of arylaldehydes, benzotriazole, and ammonia in dry ethanol. Deprotonation of these imines with butyllithium yields N-lithiated azomethine ylides 2 which readily undergo 1,3-dipolar cycloaddition with a large range of dipolarophiles. The cyclisations are regiospecific and generally exhibit high stereoselectivity. Benzotriazolate is eliminated during the course of the reaction, and the method thereby provides a route to 2,5-diaryl substituted pyrroles, 3,4-dihydro-2H-pyrroles and c-ring fused 3,4-dihydro-2H-pyrroles.