Phosphorus-based directed metalation groups (DMGs): Suzuki-Miyaura cross coupling of di-t-butylphosphine oxide and development of di-t-butylphosphine sulfide for use as a DMG

A protocol for the Suzuki-Miyaura Cross coupling of sterically hindered aryl phosphine oxides has been developed. (Di-t-butyl-phosphinoyl)-2-iodo-benzene was reacted with various aryl boronic acids under optimized conditions (K 3PO4/Pd(OAc)2/PhMe) to give the corresponding biaryl phosphine oxides in good yields. Subsequent reduction of biaryl phosphine oxides to give the desired biaryl phosphines was not possible.; Conditions for Directed ortho Metalation using di- t-butylphosphine sulfide as the directed metalation group has been developed. A variety of 1,2-disubstituted aryl phosphine sulfides have been synthesized in good yield from the metalation of (di-t-butyl-phosphinothioyl)-benzene (n-BuLi/TMEDA/Et2O) and quench with various electrophiles.; Reduction of (2-di-t-butyl-phosphinothioyl)-biphenyl using Raney Ni proceeded easily and gave a yield of 80%. This reduction has not yet been extended to the other aryl phosphine sulfides synthesized.