Stepwise mechanism of formal 1, 5-sigmatropic rearrangement of dimethyl 3, 3-dialkyl-3H-pyrazole-4, 5-dicarboxylates

MW Majchrzak, E Jefferson…

Index: Majchrzak, Michael W.; Jefferson, Elizabeth; Warkentin, John Journal of the American Chemical Society, 1990 , vol. 112, # 6 p. 2449 - 2451

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Citation Number: 15

Abstract

Compounds 1 (Scheme II) were prepared by in situ cycloaddition of the appropriate diazoalkanes to dimethyl acetylenedicarboxylate. The diazoalkanes were generated by photolysis of oxadiazolines." Pyrazoles la and lb were isolated before thermolysis in benzene at 160 OC (sealed tube) whereas IC and Id rearranged in the medium in which they were formed. Thermolysis of la afforded 2a (-83%), 3a (-9%), and several