Synlett 2023; 34(05): 445-450
DOI: 10.1055/s-0042-1751417
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Special Edition Thieme Chemistry Journals Awardees 2022

Catalyst Comparison for Additive-Free Acceptorless Dehydro­genation of Indoline Derivatives

James M. Stubbs
,
Amrit S. Nanuwa
,
Matthew D. Hoffman
,
This work was financially supported by a Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Grant. J.M.S. thanks the Ontario Graduate Scholarship program for funding.


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Abstract

A group of thirteen catalysts of type [Ru(Cp/Cp*)(P–P)(MeCN)]PF6, bearing cooperative or noncooperative bidentate phosphine ligands, were evaluated for the catalytic acceptorless dehydrogenation of indoline. The systematic comparison revealed that the optimal cooperative catalyst structure included a Cp ancillary ligand, and an N,N-disubstituted P,P-disubstituted 1,5-diaza-3,7-diphosphacyclooctane ligand, denoted as (PR 2NR′ 2). A cooperative complex bearing a PPh 2NPh 2 ligand exhibited about a twofold longer lifetime than a noncooperative analogue with (diphenylphosphino)ethane (dppe) as the supporting bisphosphine ligand. The cooperative catalyst effectively dehydrogenated a range of indoline substrates to give substituted indoles.

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Publication History

Received: 02 December 2022

Accepted after revision: 18 January 2023

Article published online:
15 February 2023

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