Iridium-Catalyzed Asymmetric Hydrogenation of Unfunctionalized, Trialkyl-Substituted Olefins

Chiral iridium complexes with bicyclic pyridine‐based N,P ligands have emerged as efficient catalysts for the enantioselective hydrogenation of unfunctionalized trialkyl‐substituted olefins. Optimization of the reaction conditions by variation of the solvent, pressure, and temperature led to enantio...

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Bibliographic Details
Published in:	Chemistry, an Asian journal Vol. 6; no. 2; pp. 599 - 606
Main Authors:	Wang, Aie, Fraga, Rui P. A., Hörmann, Esther, Pfaltz, Andreas
Format:	Journal Article
Language:	English
Published:	Weinheim WILEY-VCH Verlag 01-02-2011 WILEY‐VCH Verlag Wiley Subscription Services, Inc
Subjects:	Alkenes - chemistry asymmetric catalysis Catalysis Chemistry Hydrogenation iridium Iridium - chemistry N,P ligands olefins P ligands
Online Access:	Get full text
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Summary:	Chiral iridium complexes with bicyclic pyridine‐based N,P ligands have emerged as efficient catalysts for the enantioselective hydrogenation of unfunctionalized trialkyl‐substituted olefins. Optimization of the reaction conditions by variation of the solvent, pressure, and temperature led to enantiomeric excesses of up to 99 %. Three pure alkenes, (E)‐2‐cyclohexyl‐2‐butene and (E)‐ and (Z)‐3,4‐dimethyl‐2‐pentene were converted into the corresponding chiral alkanes with 97 %, 94 %, and 93 % ee, respectively. Hydrogenation of the three CC bonds of both α‐ and γ‐tocotrienyl acetate led to α‐ and γ‐tocopheryl acetate with very high diastereoselectivity. The same catalysts were successfully applied in the hydrogenation of trisubstituted alkenes with a carboxylic ester or a keto group in the γ position. This reaction was used as a key step in a highly enantioselective synthesis of the pheromone of the caddisfly Hesperophylax occidentalis. The hydrogenation of a structurally analogous allylic alcohol also gave high enantioselectivities. Unfunctionalized trialkyl‐substituted olefins are hydrogenated with high efficiency and excellent enantioselectivity using iridium complexes derived from chiral N,P ligands. In this way, pharmaceutically interesting and industrially relevant compounds with chiral alkyl fragments are easily accessible with high diastereo‐ and enantioselectivities.
Bibliography:	Swiss National Science Foundation Federal Commission for Technology and Innovation (KTI) Novartis Pharma FCT istex:AF5FB855425199494ACACBF7AD10836AC7F65D79 ark:/67375/WNG-G0KB78H2-9 ArticleID:ASIA201000595 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1861-4728 1861-471X
DOI:	10.1002/asia.201000595