Shuiqing Liu , Baoping Ling , Siwei Bi , Rongyue Wang
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引用次数: 0
Abstract
The mechanism of Ru(ii)-catalyzed gem-hydrogenation of 1,3-enynes was studied with the aid of DFT calculations. The origins of cyclization selectivity involved in the two Ru(ii)-catalyzed hydrogenative cyclization reactions, where reaction A bears an –OMe group and reaction B bears an –OSiMe3 group, were explored explicitly. For reaction A, the thermodynamically unfavorable chair-to-twist boat isomerization is found to be involved in the process of forming a five-membered carbocycle product (P′), thus leading to the formation of the preferred five-membered heterocycle product (P). In contrast, for reaction B, the low electronegativity of the silicon atom in –OSiMe3 makes the proton transfer from the methyl group to the carbene atom more difficult to form a six-membered heterocycle product (P1′), thus leading to the preferred five-membered carbocycle product (P1). Additionally, the influence of a series of heteroatoms on the cyclization selectivity was predicted theoretically (reaction A with –XMe (X = O, S, Se and Te) and reaction B with –OYMe3 (X = C, Si, Ge and Sn)).
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