Synthesis of β‐Aryl‐α,β‐Dehydroaminophosphonates by Pd‐Catalyzed Fujiwara–Moritani C−C Coupling

Abstract

The treatment of diethyl α,β‐dehydroaminophosphonate 1 with various arenes (ArH=toluene 2 a, benzene 2 b, anisole 2 c, bromobenzene 2 d, chlorobenzene 2 e, benzyl alcohol 2 f, p‐xylene 2 g) in acetic acid (AcOH) at 120 °C for 8 h in the presence of Pd(OAc)2 (10 % mol, OAc=acetate) and AgOAc (3.4 equivalents) results in the formation of the corresponding β‐aryl derivatives E‐Ar(H)C=C(NHAc)P(O)(OEt)2 3 a–3 g. The reaction proceeds through double C−H activation (arene and alkene) and subsequent C−C oxidative coupling (Fujiwara–Moritani reaction), processes catalyzed by Pd and assisted by Ag. The obtained products 3 a–3 g are isosteric analogs of phenylalanine and are obtained with high selectivity. Thus, geometrical E‐isomers have been obtained in all studied cases, however mixtures of ortho‐/meta‐/para‐isomers are observed when the activated position in the starting arene 2 is considered.