Some ring expansion and related reactions of the phosphindole system

Abstract

3‐Butyl‐1,2‐diphenylphosphindole reacts smoothly with ethyl propiolate and water and with benzoyl chloride and water to give ring expanded products. The second of these products is further expanded to a seven‐membered system by treatment with sodium hydride. With diiodo‐methane followed by hydroxide ion, cleavage of the phosphorus‐containing ring occurs. The nmr and mass spectral data are analyzed in detail and the results are discussed in the context of related studies with simple phospholes and dibenzophospholes. Some of the results further illustrate that predictions regarding the types of reaction entered into by phosphorus heterocycles must be made with caution. Copyright © 1976 Journal of Heterocyclic Chemistry