Synthesis 2004(13): 2135-2152  
DOI: 10.1055/s-2004-831166
PAPER
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Preparation of (E)-α-Bromoacrylates from Mixtures of Brominated­ Ando Phosphonates

Thomas Olpp, Reinhard Brückner*
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstr. 21, 79104 Freiburg, Germany
Fax: +49(761)2036100; e-Mail: reinhard.brueckner@organik.chemie.uni-freiburg.de;
Further Information

Publication History

Received 31 March 2004
Publication Date:
13 August 2004 (online)

Abstract

We prepared 69:31-11:89 mixtures of phosphonates 6b and 7b containing two phenoxy substituents, a CO2Et group, and 1 or 2 bromine atoms, respectively, at the interspersed methylene group. Deprotonating 64:36 mixtures of these reagents with NaH and adding a variety of aldehydes at 0 °C provided unsaturated α-bromoesters. Yields were typically 70-99% and E-selectivities (i.e. ester and β-substituent cis) 80:20-98:2. Similarly, we proceeded via the chlorinated phosphonate 49 to the unsaturated α-chloroester 51 with E:Z = 94:6 (80%).

25

Aldehyde 23: Courtesy of BASF AG.

27

Preparation of aldehydes 35 and 39: Olpp, T., Universität Freiburg, unpublished work.

29

Aldehyde 43 was generously provided by Professor J. Podlech, Universität Karlsruhe.