The intriguing methoxycarbonylation of trimethylsilylacetylene in the presence of Drent's catalytic system
Roberto Sole, Alberto Scrivanti, Md. Mahbubul Alam, Valentina Beghetto
Abstract
The alkoxycarbonylation of trimethylsilylacetylene has been studied in order to develop an atom economic sustainable synthesis of 2‐(trimethylsilyl)acrylates, a family of valuable intermediates. Pd(OAc) 2 in combination with CH 3 SO 3 H and diphenyl‐(pyridin‐2‐yl)phosphine or diphenyl‐(6‐methyl‐pyridin‐2‐yl)phosphine is an active catalyst for the reaction affording mixtures of the sought 2‐(trimethylsilyl)acrylate and the isomeric 3‐(trimethylsilyl)acrylate. The phosphine ligand has a dramatic effect on the reaction. When employing diphenyl‐(pyridin‐2‐yl)phosphine, it is necessary to carry out the reaction at 80°C in order to observe a modest catalytic activity, and the product is an almost equimolecular mixture of the two isomeric esters. On the contrary, when employing diphenyl‐(6‐methyl‐pyridin‐2‐yl)phosphine, the reaction proceeds under much milder conditions affording with high rate (turnover frequency [TOF] up to 1200 h −1 ) and selectivity (>95%) of the sought 2‐(trimethylsilyl)acrylate. The reaction conditions have been optimized, and the effects of phosphine/palladium, acid/palladium, reaction time, temperature, and CO pressure have been investigated.