Synthesis and butyllithium-induced cyclisation of 2-benzyloxyphenylphosphonamidates giving 2,3-dihydrobenzo[d][1,3]oxaphospholes

Abstract

A series of fourteen O-ethyl-N-butylphenylphosphonamidates with benzyl ether substituents at the ortho position have been prepared and fully characterised. Upon treatment with n-butyllithium in THF at RT, these undergo cyclisation in eight cases to give the novel 2,3-dihydrobenzo[d][1,3]oxaphospholes in moderate to low yield as a single diastereomer for which the relative configuration has been determined by X-ray diffraction in one case.