Rational design of novel ligands for environmentally benign cross-coupling reactions

Transition-metal (TM) complexes of new phosphines, readily prepared by a straight forward three-step modular synthesis, were successfully employed in difficult cross-coupling reactions conducted under mild conditions (water, open-flask, low temperature) that aspire to meet green chemistry criteria. High yielding catalyzed by bismuth or rhodium complexes oxidative arylation of naphthoquinone gave the key 2-arylnaphthoquinone intermediates for facile bismuth triflate-catalyzed Michael addition of secondary phosphine oxides. Subsequent O-methylation and reductions of the resulting products gave access to the target air-stable phosphine ligands in good overall yields (up to 60 %).