Catalytic Deoxydehydration of Diols to Olefins by using a Bulky Cyclopentadiene‐based Trioxorhenium Catalyst

A bulky cyclopentadienyl (Cp)‐based trioxorhenium compound was developed for the catalytic deoxydehydration of vicinal diols to olefins. The 1,2,4‐tri( tert ‐butyl)cyclopentadienyl trioxorhenium ( 2 ) catalyst was synthesised in a two‐step synthesis procedure. Dirhenium decacarbonyl was converted into 1,2,4‐tri( tert ‐butyl)cyclopentadienyl tricarbonyl rhenium, followed by a biphasic oxidation with H 2 O 2 . These two new three‐legged compounds with a ‘piano‐stool’ configuration were fully characterised, including their single crystal X‐ray structures. Deoxydehydration reaction conditions were optimised by using 2 mol % loading of 2 for the conversion of 1,2‐octanediol into 1‐octene. Different phosphine‐based and other, more conventional, reductants were tested in combination with 2 . Under optimised conditions, a variety of vicinal diols (aromatic and aliphatic, internal and terminal) were converted into olefins in good to excellent yields, and with minimal olefin isomerisation. A high turnover number of 1400 per Re was achieved for the deoxydehydration of 1,2‐octanediol. Furthermore, the biomass‐derived polyols (glycerol and erythritol) were converted into their corresponding olefinic products by 2 as the catalyst.