ArCH(OMe)2-A PtIV-catalyst originator for diverse annulation catalysis

Abstract

We discover an important property of a small molecule ArCH(OMe)2 which transforms catalytically inactive PtIIBr2 procatalyst in situ to an powerful catalyst PtIV-species for diverse annulation reaction. The powerful catalytic system enables selective activation of C2-H/N-H and C2-H/C4-H of acetoacetanilide and C5O/C;C of substituted butyne-1,2-dione for C-C/C-N, C-C/C-C and C-O/C-O bond-forming inter- and intramolecular annulation towards direct syntheses of functionalised 2-pyridones, cyclohexenones and 3(2H)-furanones respectively. In contrast to the common ligand, herein highly labile C-OMe bond of ArCH(OMe)2 is expected to react with PtBr2 towards generation of the high-valent active catalyst. Unlike catalyst promoter or initiator, the reaction does not occur with PtBr2 in the absence of ArCH(OMe)2. In situ generation of PtIV-species and -OMe fragment of ArCH(OMe)2 were confirmed from the UV-vis characteristic peaks about 260 nm and trapping of -OMe group respectively. These observations provide new prospects and perspectives in catalysis for innovative catalyst design.