X=Y-ZH COMPOUNDS AS POTENTIAL 1,3-DIPOLES .44. ASYMMETRIC 1,3-DIPOLAR CYCLOADDITION REACTIONS OF IMINES AND CHIRAL CYCLIC DIPOLAROPHILES

摘要

Metallo - 1,3-dipoles generated in situ from both aryl and aliphatic imines of a-amino esters by the action of silver salts and tertiary amines undergo cycloaddition at room temperature to 5R-(1'R, 2'S, 5'R-menthyloxyl) - 2(5H)-furanone and to N-acetyl-5R-isopropoxy-2(5H)-pyrrolone giving homochiral cycloadducts in good yield in all cases. pi-Interaction between the dipolarophile carbonyl group and the aryl group in the aryl imines is not required for good induction. The stronger the base the faster the cycloaddition with 2-t-butyl-1,1,3,3-tetramethylguanidine > DBU > NEt(3). X-Ray crystal structures of representative cycloadducts establish the absolute configuration of the pyrrolidine stereocentres. [References: 14]