THE PREPARATION AND DECOMPOSITION OF ALKYL 2-DIAZOPENT-4-ENOATES AND 1-TRIMETHYLSILYL-1-DIAZOBUT-3-ENES

Article abstract of DOI:10.1016/S0040-4020(01)89947-6

The pyrazolines (12), (18), (21), (26) and (32), prepared by addition of diazomethane to alkyl cyclopropene-1-carboxylates or to 1-trimethylsilylcyclopropenes respectively, rearrange at 20 to 70 deg C to diazo-compounds (14), (19), (23), (28) and (36).Pyrazolines (22) and (33) are unchanged under these conditions.Catalytic decomposition of the diazo-compounds is highly dependent on the nature of the substituents and on the catalyst, leading to bicyclobutanes or dienes apparently derived by intramolecular addition, hydrogen shifts or vinyl shifts in intermediate carbenoids.In the case of (36) decomposition in the presence of rhodium acetate leads cleanly to the Z-alkene (37) while in the presence of PdCl2(CH3CN)2 the E-isomer (38) is produced.