Room temperature palladium-catalyzed hydroarylation of ynamides in water

Abstract

Pd-catalyzed hydroarylation reactions of ynamides were studied in pure water in the presence of the water-soluble industrial TPPTS ligand in comparison with the use of PCy3 or P(o-Tol)3. Pd(OAc)2/TPPTS (3,3′,3″-phosphanetriyltris(benzenesulfonic acid) trisodium salt) system exhibited high activity for the conversion of various aryl- and alkyl-ynamides in the presence of arylboronic acids bearing either electron-donating and electron-withdrawing groups. The hydroarylation reactions allowed the formation of (Z)-α,β-disubstituted enamides as major compounds in the case of arylynamides and as unique isomer in the case of alkylynamides. The reaction conditions were optimized and the presence of a base was necessary for the efficient preparation of enamides at room temperature. Conversely, α,β-disubstituted or β,β′-disubstituted enamides were isolated as major single stereoisomers and at room temperature in water in the absence of any additive by using PCy3 or P(o-Tol)3, respectively. The best activity was observed for oxazolidin-2-one, whereas other a tosylynamide was non-reactive.