Synthesis of five-membered unsaturated compounds from ketones via cyanophosphates under neutral conditions: [1,5]-CH insertion of alkylidene carbenes generated by tetrazole fragmentation

Cyanophosphates (CPs) can easily be prepared via the reactions of carbonyl compounds with diethyl phosphorocyanidate (DEPC) in the presence of LiCN (cat.) under non-aqueous conditions. Treatment of ketone-derived CPs with TMSN3/Bu2SnO (cat.) in toluene at reflux produces cyclopentenes or heterocyclic products in good yields under neutral conditions. In this two-step transformation, CPs may form tetrazolylphosphates, which subsequently undergo successive fragmentation to generate alkylidene carbenes, which undergo [1,5]-C-H insertions to yield five membered compounds.

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