Exploring the nucleophilicity of N,N '-diamidocarbenes: Heteroallenes and related compounds as coupling reagents

Abstract

The propensity of a stable N,N'-diamidocarbene (DAC) to react with various heteroallenes was explored. The DAC condensed with 4-nitrophenyl azide as well as 4-nitrophenyl isothiocyanate to afford the respective acyclic triazene or zwitterionic dihydropyrimidinium imidothiolate products. Treating the DAC with two equivalents of 3-nitrophenyl isocyanate afforded an iminooxazolidinone rather than the expected hydantoin. Similarly, the addition of diphenylketene to the DAC afforded a dioxolane product, whereas analogous reactions involving N-heterocyclic carbenes (NHCs) resulted in betaine adducts. Although the DAC as well as various diaminocarbenes condensed with 2,6-dimethoxyphenyl nitrile N-oxide to afford the respective nitrosoethylenes, only the six-membered DAC and NHC adducts rearranged to the corresponding nitrones at elevated temperature.