Methanol as a Hydrogen Source in Pd(II)-Bis-N-Heterocyclic Carbenes Mediated Catalytic Semi-reduction of Alkyne Under Mild Condition

G, Prabusankar and Arruri, S and Gembali, R and Chatla, N (2017) Methanol as a Hydrogen Source in Pd(II)-Bis-N-Heterocyclic Carbenes Mediated Catalytic Semi-reduction of Alkyne Under Mild Condition. Asian Journal of Organic Chemistry. ISSN 2193-5807 (In Press)

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Abstract

A series of six new monoorgano-palladium compounds of the form LPdX2 (L = [4,5-bis{(N-methyl imidazol-2-ylidene)methyl}ethane] (6), [4,5-bis{(N-vinyl imidazol-2-ylidene)methyl}ethane] (7), [4,5-bis{(N-isopropyl imidazol-2-ylidene)methyl}ethane] (8), [4,5-bis{(N-2,6-dimethyl phenyl imidazol-2-ylidene)methyl}ethane] (9), [4,5-bis{(N-4-ethyl benzoate imidazol-2-ylidene)methyl}ethane] (10), [4,5-bis{(N-isopropyl imidazol-2-ylidene)methyl}acridine] (11); X = Br for 6-9 and 11, X = Cl for 10) was synthesized and characterized by FT-IR spectroscopy, 1H NMR and 13C NMR spectroscopy, elemental analysis, and X-ray crystallography. In the solid state, molecules 6-11 are neutral and possess one ligand and two halides in nearly ideal square-planar geometry. These molecules are catalytically competent for the semi-hydrogenation of diphenylacetylene reaction. Notably, methanol was used as a hydrogen source for the first time. Among these catalysts, the acridine bridged bis-N-heterocyclic carbene palladium complex gave excellent selectivity towards the formation of Z-alkenes from internal alkynes. Fifteen different alkynes were subjected under investigations and the reactions were proceeded with very high diastereo selectivity under mild conditions.

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