Chemistry Publications

Title

Optimizing ligand structure for low-loading and fast catalysis for alkynyl-alcohol and-amine cyclization

Document Type

Article

Publication Date

1-1-2019

Journal

Dalton Transactions

Volume

48

Issue

22

First Page

7928

Last Page

7937

URL with Digital Object Identifier

10.1039/c9dt01870k

Abstract

A series of [Ru(Cp/Cp∗)(PR2NR′2)(MeCN)]PF6 complexes were prepared, in which the steric and electronic properties of the primary coordination sphere were varied (R = Ph, t-Bu, Bn; and Cp vs. Cp∗). These complexes were catalytically active in the cyclization of alkyne substrates with an intramolecular nucleophile (amine or alcohol) to produce 5-and 6-membered heterocycles. The effect of the 1° coordination sphere structure on catalyst performance was evaluated. Steric bulk around the metal centre was a key feature to achieve rapid catalysis at low temperatures. The catalyst [Ru(Cp)(Pt-Bu2NPh2)(MeCN)]PF6 gave a turnover number that was >1 order of magnitude more active than previous catalysts in the cyclization of the benchmark substrate 2-ethynylaniline. This catalyst is tolerant of a diversity of functional groups and is competent at the formation of various substituted indoles.

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