A total synthesis of 1, 2-dehydro-1-carbacephalosporin 2 (R²=CH₃) is described. The azido-azetidinone 8, prepared from the Schiff base 5, azidoacetyl chloride and triethylamine, was converted to the ylide 13 via 10. Conjugate addition of benzenethiol to 13 followed by an intramolecular Wittig reaction gave the 1-carbacephem derivatives 16, which were transformed to the sulfoxides 17. Treatment of 17 with triethylamine yielded the 1, 2-dehydro derivative 18. The carboxylic acid derivatives 19, and 23, prepared from 18, did not show antibacterial activity.