Mechanistic Study on Oxorhenium-Catalyzed Deoxydehydration and Allylic Alcohol Isomerization

摘要

The reaction mechanism of 1,2 x n-deoxydehydration (DODH; n = 1, 2, 3 ...) reactions with 1-butanol as a reductant in the presence of methyltrioxorhenium(VII) catalyst has been investigated by DFT. The reduced rhenium compound, methyloxodihydroxyrhenium(V), serves as the catalytically relevant species in both allylic alcohol isomerization and subsequent DODH processes. Compared with three-step pathway A, involving [1,3]-transposition of allylic alcohols, direct two-step pathway B is an alternative option with lower activation barriers. The rate-limiting step of the DODH reaction is the first hydrogen transfer in methyltrioxorhenium( VII) reduction. Moreover, the increase in the distance between two hydroxyl groups in direct 1,2 x n-DODH reactions for C4 and C6 diols results in a higher barrier height.