Palladium [ ^t‑Bu(PCP)PdOH] Pincer Complex as a Catalyst in the Michael Reaction

The Michael reaction is a versatile carbon-carbon bond-forming strategy that is efficiently catalyzed by transition metal complexes. We report that the palladium [ ^t‑Bu(PCP)-PdOH] pincer complex effectively activates substrates and forms stable complexes with ketones. The reactive intermediate [ ^t‑Bu(PCP)-Pd-(acac)] complex, which is formed in situ from acetylacetone and the [ ^t‑Bu(PCP)-PdOH] complex, was successfully isolated and structurally characterized by single-crystal X-ray diffraction. This complex serves as an active catalyst in the reaction between acetylacetone and various trans-nitrostyrenes, providing the corresponding Michael adducts in high isolated yields (87-98%). The reaction proceeds under mild conditions with a low catalyst loading, short reaction times, and often minimal or no solvent. These results show that PCP-palladium pincer complexes can serve as efficient, practical catalysts for C-C bond-forming condensation reactions.