Synthesis of P-Substituted 5- and 6-Membered Benzo-Phostams: 2,3-Dihydro-1 H-1,2-benzazaphosphole 2-Oxides and 2,3-Tetrahydro-1 H-1,2-benzazaphosphinine 2-Oxides

J Org Chem. 2021 Nov 5;86(21):14684-14694. doi: 10.1021/acs.joc.1c01501. Epub 2021 Oct 11.

Abstract

Several approaches were developed for the preparation of phosphorus-substituted 5- and 6-membered benzophostams. Carbodiimide-promoted cyclization of zwitterionic aminophosphinates derived from a nitrobenzene precursor accomplished the cyclization in good yields. Alternatively, a novel copper-catalyzed cross-coupling between a phosphonamide and a bromobenzene precursor produced the heterocycles in moderate to good yields. Three different methods are compared for the synthesis of the P-ethoxy-substituted 5-membered benzophostam.