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Synlett 2008(20): 3091-3105  
DOI: 10.1055/s-0028-1087360
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© Georg Thieme Verlag Stuttgart ˙ New York

DBU-Promoted Elimination Reactions of Vicinal Dibromoalkanes Mediated by Adjacent O-Functional Groups, and Applications to the Synthesis of Biologically Active Natural Products

Tadaaki Ohgiya*, Noriki Kutsumura, Shigeru Nishiyama*
Department of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan
Fax: +81(42)3950312; e-Mail: t-ogiya@kowa.co.jp; Fax: +81(45)5661717; e-Mail: nisiyama@chem.keio.ac.jp;
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Publication History

Received 28 February 2008
Publication Date:
24 November 2008 (online)

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Abstract

Regioselective elimination reactions of 1,2-dibromo­alkanes possessing aryloxy or acyloxy groups at the C-3 position can be carried out under mild basic conditions to produce the corresponding 2-bromo-1-alkenes. The regioselectivity of these processes is controlled by the acidity enhancement of hydrogens at C-2 caused by the inductive electron-withdrawing effects of substituents at C-3. A similar acidity enhancement of the hydrogens at C-1 causes selective DBU-promoted, two-step transformations of 1,2-dibromo­alkanes to alkyne derivatives. The 2-bromo-1-alkenes and alkynes, readily prepared using these regioselective elimination reactions, have been employed as key intermediates in the synthesis of biologically active natural products.

1 Introduction

2 Regioselective Elimination

2.1 Simple Synthesis of 2-Bromo-1-alkenes

2.2 Total Synthesis of (-)-Tuliparin B

2.3 Total Synthesis of (+)-Tanikolide

2.4 Total Synthesis of Tremetones

2.5 Elimination Reactions of 1-Acyloxy-4-aryl-2,3-dibromoalkanes

2.6 The Effect of C-4 Electron-Withdrawing Groups on HBr Elimination Reactions

3 Alkyne Synthesis

3.1 Two-Step Elimination Reactions with DBU

3.2 Total Synthesis of (-)-Muricatacin and (-)-(R,R)-Sapinofuranone B

4 Summary

Key words

bromoalkenes - alkynes - dibromoalkanes - regioselective elimination - acidity enhancement

14

The ratio was determined by ¹H NMR integration.

27

The optical purity was determined from the 400-MHz ¹H NMR spectrum of the corresponding MTPA esters.