Phosphaspiropentene as a Transient Intermediate

A phosphaspiropentene is the plausible kinetic product from the addition of dichlorocarbene to a phosphatriafulvene, which rearranges to a novel P-substituted triafulvene. The calculated barrier of 18.6 kcal mol - 1 for this process is consistent with the temperature of -40 °C at which this reaction proceeds.