Stereoselective 1,3Dipolar Cycloadditions to (S)-1Benzoyl3-(cyanomethylidene)-5-(methoxycarbonyl)pyrrolidin-2-one (original) (raw)

1998, Helvetica Chimica Acta

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 cycloadditions 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-diazaspiro[4,4]non-1en-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 11, respectively, and Et 3 N, 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 presence of Et 3 N, led to pyrrolo [3,4-d]isoxazole 16 in 85% de.