CYCLOPROPYL BUILDING-BLOCKS FOR ORGANIC-SYNTHESIS .42. AN UNPRECEDENTED MODE OF RING-OPENING OF METHYLENECYCLOPROPANE MOIETIES - REACTIONS OF METHYLENECYCLOPROPANECOPPER REAGENTS WITH AN ELECTROPHILIC GLYCINE EQUIVALENT

The reactions of ethyl 2-acetoxy-2-diphenylmethyleneaminoacetate (1) w ith organocopper reagents derived from bicyclopropylidene (2) and meth ylenecyclopropane (3) are accompanied by an unusual mode of opening of one three-membered ring to give 1-methylene-1,2,3,4-tetrahydropyridin e derivatives 8a, 9 in good yields. The cuprate derived from methylene spiropentane (4) reacts with 1 to yield both the normal substitution p roduct 14 (37%) as well as the rearrangement product 15 (34%), while t he simple cyclopropylcuprate undergoes substitution to give the protec ted cyclopropylglycine 16 (75%) without rearrangement. The tetrahydrop yridine 8a shows an interesting tautomerism in solution. The 4-cyclopr opylidenetetrahydropyridine 15 undergoes an unusual dehydrodimerizatio n to produce two separable rotamers, C-2-19 and C-1-19, via 18.