Synlett 2011(14): 2043-2047  
DOI: 10.1055/s-0030-1260983
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Catalytic, Asymmetric, Bromine-Induced Semipinacol Rearrangements at Unactivated Double Bonds

Christian H. Müller, Michael Wilking, Ansgar Rühlmann, Birgit Wibbeling, Ulrich Hennecke*
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
Fax: +49(251)8336523; e-Mail: ulrich.hennecke@uni-muenster.de;
Further Information

Publication History

Received 22 July 2011
Publication Date:
03 August 2011 (online)

Abstract

A new catalyst system for the enantioselective bromine-induced semipinacol rearrangement of cyclic allylic alcohols is described. Using the commercially available (DHQD)2Pyr catalyst the products containing an all-carbon quaternary chiral centre can be obtained in good yield and high enantioselectivity.

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See Supporting Information for details. The complete crystallographic data can be obtained under the deposition numbers CCDC 835983 and 835982 from the Cambridge Crystallographic Data Centre.

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Considering Tu’s latest results¹² one reviewer questioned the role of small amounts of water in the system. We used commercially available ‘dry’ solvents stored over molecular sieves for all reactions. The deliberate addition of 5 equivalents of water to the rearrangement of 1a under standard conditions did not change the enantioselectivity. Addition of methanol (5 equiv) or molecular sieves to the reaction was detrimental for the enantioselectivity (33% and 60% ee, respectively).