Different Behavior of 2-Substituted 3-Nitro-2 H -chromenes in the Reaction with Stabilized Azomethine Ylides Generated from α-Iminoesters.

The AgOAc-catalysed reaction of 3-nitro-2-phenyl-2 H -chromenes with stabilized azomethine ylides generated from the imines based on methyl glycinate and arylaldehydes leads to a mixture of endo and endo ' isomers of the corresponding chromeno[3,4- c ]pyrrolidines in a ratio of 2.0-2.3:1 in 85-93% total yields as a result of a Michael addition/Mannich reaction sequence. In a similar reaction involving 2-trifluoromethyl-3-nitro-2 H -chromenes, only endo chromeno[3,4- c ]pyrrolidines are formed in 85-94% yields. 3-Nitro-2-(trichloromethyl)-2 H -chromenes under the same conditions react with these azomethine ylides to give the corresponding Michael adducts as individual anti -isomers with the cis , trans -configuration of the chromane ring in 40-67% yields. Some 4-CF 3 -substituted chromano[3,4- c ]pyrrolidines exhibited high cytotoxic activity against HeLa human cervical carcinoma cells.