title: Chirality Transfer in Gold(I)-Catalysed Direct Allylic Etherifications of Unactivated Alcohols: Experimental and Computational Study.
abstract: Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mechanistic subtleties of the chirality-transfer process. Crucially, addition of molecular sieves was found to be necessary to ensure efficient and general chirality transfer. Computational studies suggest that the efficiency of chirality transfer is linked to the aggregation of the alcohol nucleophile around the reactive π-bound Au-allylic ether complex. With a single alcohol nucleophile, a high degree of chirality transfer is predicted. However, if three alcohols are present, alternative proton transfer chain mechanisms that erode the efficiency of chirality transfer become competitive.
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (UK).
authors.forename: Graeme
authors.initials: G
authors.lastname: Barker
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (UK).
authors.forename: David G
authors.initials: DG
authors.lastname: Johnson
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (UK).
authors.forename: Paul C
authors.initials: PC
authors.lastname: Young
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (UK). S.A.Macgregor@hw.ac.uk.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Macgregor
authors.affiliation: Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (UK). A.Lee@hw.ac.uk.
authors.forename: Ai-Lan
authors.initials: AL
authors.lastname: Lee
keywords: alcohols; allylations; asymmetric reactions; chirality transfer; gold