Reaction of carbethoxycarbene with 2-phenyloxirane and 2-phenyloxetane

Thermal or photochemical decomposition of ethyl diazoacetate in 2-phenyloxirane gave a complex mixture, the analysis of which indicated that the reaction of carbethoxycarbene had proceeded according to the scheme summarized in Fig. 1. The reaction probably involves intermediate formation of an oxygen-ylide (IV), thus accounting for the observed oxygen-transfer and oxetane formation. Copper-catalysed thermal decomposition resulted in a more selective distribution of products, secondary reactions as well as the tar-formation being drastically reduced. The action of other carbenes such as dihalo-, phenyl- and diphenyl-carbene yielded less or no oxygen-transfer products and the formation of oxetane was not observed. In some cases, especially in the reaction of bis(benzene-sulphonyl)carbene, the major product was cyclic dimers of 2-phenyloxirane.

2-Phenyloxetane reacts more selectively with carbethoxycarbene to produce a mixture of cis and trans isomers of 2-carbethoxy-3-phenyltetrahydrofuran in 72–80% yield.