An unusually unstable ortho-phosphinophenol and its use to prepare benzoxaphospholes having enhanced air-stability

Abstract

The primary phosphine 3,5-di-tert-butyl-2-phosphinophenol has been prepared and characterized. Oddly, the presence of a sterically demanding tert-butyl group adjacent to the PH₂ centre renders the molecule very sensitive to loss of PH₃ and formation of 3,5-di-tert-butyl-phenol in chloroform solutions in the presence of air. The process was catalyzed by HCl and dependent on the purity of CDCl₃. Despite the instability of 3,5-di-tert-butyl-2-phosphinophenol, this material could be employed to produce a series of luminescent 2-R-4,6-di-tert-butyl-1,3-benzoxaphospholes having greater air stability than corresponding less bulky 2-R-1,3-benzoxaphospholes.