Double-Asymmetric Hydrogenation Strategy for the Reduction of 1,1-Diaryl Olefins Applied to an Improved Synthesis of CuIPhEt, a C-2-Symmetric N-Heterocyclic Carbenoid

by Spahn, E.; Albright, A.; Shevlin, M.; Pauli, L.; Pfaltz, A.; Gawley, R. E.

A library of iridium and rhodium phosphine catalysts have been screened for the double-asymmetric hydrogenation of 2,6-di-(1-phenylethenyl)-4-methylaniline to produce the C-2-symmetric aniline precursor of the N-heterocyclic carbenoid CuIPhEt. The best catalyst produced the desired enantiomer in 98.6% selectivity. This rare example of a highly selective hydrogenation of a 1,1-diaryl olefin enables a four-step asymmetric synthesis of the C-2-symmetric phenylethyl imidazolium ion (IPhEt) from p-toluidine and phenylacetylene and its conversion to the hydrosilylation catalyst CuIPhEt.

Journal
Journal of Organic Chemistry
Volume
78
Issue
6
Year
2013
Start Page
2731-2735
URL
https://dx.doi.org/10.1021/jo3026548
ISBN/ISSN
1520-6904; 0022-3263
DOI
10.1021/jo3026548