Highly Enantioselective Reductive Cyclization of Acetylenic Aldehydes via Rhodium Catalyzed Asymmetric Hydrogenation

Jong Uk Rhee and Michael J. Krische*
University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, Texas 78712
J. Am. Chem. Soc., 2006, 128 (33), pp 10674–10675
DOI: 10.1021/ja0637954
Publication Date (Web): August 1, 2006
Copyright © 2006 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, mkrische@mail.utexas.edu

Abstract

Abstract Image

Catalytic hydrogenation of acetylenic aldehydes 1a−12a using chirally modified cationic rhodium catalysts enables highly enantioselective reductive cyclization to afford cyclic allylic alcohols 1b−12b. Using an achiral hydrogenation catalyst, the chiral racemic acetylenic aldehydes 13a−15a engage in highly syn-diastereoselective reductive cyclizations to afford cyclic allylic alcohols 13b−15b. Ozonolysis of cyclization products 7b and 9b allows access to optically enriched α-hydroxy ketones 7c and 9c. Reductive cyclization of enyne 7a under a deuterium atmosphere provides the monodeuterated product deuterio-7b, consistent with a catalytic mechanism involving alkyne−carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle. These hydrogen-mediated transformations represent the first examples of the enantioselective reductive cyclization of acetylenic aldehydes.

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History

  • Published In Issue August 23, 2006
  • Received May 30, 2006

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