A theoretical study of the carbenoids LiCH2X (X = Cl, Br, I) cyclopropanation reaction with ketene

Abstract

A computational study for the [2 + 1] addition of the lithium carbenoids LiCH2X (X = Cl, Br, I) with ketene have been investigated by means of the B3LYP hybrid density functional method. All the reactions examined displayed similar concerted mechanisms for the cyclopropanation of these reagents. The lithium carbenoids react with ketene via an asynchronous attack on one CH2 or C group of ketene with relatively low barrier to reaction in the range of 25·34–33·74 kJ/mol in THF solvent. The trend of the lithium carbenoids reaction barrier with ketene is LiCH2Cl < LiCH2Br < LiCH2I. The results show that the reactions could be highly chemical reactivity with low barriers and could be favoured in experiment. The reactions could proceed easily at lower temperature. The computational results are briefly compared to other carbenoid reactions and related species.