Stereoselective 1,3-dipolar cycloadditions to (S)-1-benzoyl-3-(cyanomethylidene)-5-(methoxycarbonyl)pyrrolidin-2-one

(5S)-1-Benzoyl-3-[(E)-cyanomethylidene]-5-(methoxycarbonyl)pyrrolidin-2-one (5) was prepared in four steps from L-pyroglutamic acid (1). 1,3-Dipolar c ycloadditions of diazomethane (6) and 2,4,6-trimethoxybenzonitrile oxide (7 ) gave substituted 1,2,7-triazaspiro[4.4]non-1-en-6-one 12 and 1-oxa-2,7-di azaspiro[4,4]non-1-en-6-one 13 in 38 and 20% de, respectively On the other hand, reaction of 5 with N-phenylbenzonitrile imines 8 and 9. generated in situ from the corresponding hydrazonoyl chlorides 10 and LL respectively, a nd Et3N, furnished racemic pyrrolo[3,4-c]pyrazoles 14 and 15 in 61 and 56% de, respectively Cycloaddition of nitrile oxide 7,when performed in the pre sence of Et3N, led to pyrrolo[3,4-d]isoxazole 16 in 85% de.