Synthesis 2004(1): 135-146  
DOI: 10.1055/s-2003-44355
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Conjugate Addition of Organozinc Compounds to Nitroolefins

Audrius Rimkus, Norbert Sewald*
University of Bielefeld, Department of Chemistry, PO Box 10 01 31, 33501 Bielefeld, Germany
Fax: +49(521)1068094; e-Mail: norbert.sewald@uni-bielefeld.de;
Further Information

Publication History

Received 22 September 2003
Publication Date:
25 November 2003 (online)

Abstract

Symmetrical (R2Zn) or mixed diorganozinc compounds (R1ZnR2) smoothly react with a series of nitroolefins in the presence of catalytic amounts of copper(I) salts and provide synthetically versatile nitro compounds in moderate to good yields. Simple alkyl groups, functionalized residues, or mixed trimethylsilylmethyl organozinc compounds (TMSM)ZnR may be employed for conjugate addition, while the TMSM group is not being transferred. ipso-Substitution is observed in absence of the copper(I) salt.

Enantiomerically pure copper(I) complexes with BINOL based chiral phosphoramidite ligands efficiently catalyze the addition of dialkylzinc compounds to nitroalkenes. For instance, diethylzinc addition occurs with high yields and excellent enantioselectivity. Nitrostyrene, 3-nitroacrolein dimethylacetal, and 3-nitroacrylates have been used as substrates. The nitroolefin moiety predominates over the acrylate moiety and acts as the more powerful Michael acceptor. 2-Alkyl-3-nitropropanoates are exclusively obtained with excellent yield and enantioselectivity. The products can easily be transformed into β2-homoamino acids, compounds of high relevance for different areas of preparative organic chemistry.

  • 1 Introduction

  • 2 Synthesis of Nitroolefins

  • 3 Conjugate Addition of Organozinc Compounds

  • 3.1 Conjugate Addition of Functionalized Organozinc Cuprates and Diorganozinc Compounds

  • 3.2 Conjugate Addition of Alkyl Trimethylsilylmethylzinc Compounds

  • 3.3 Enantioselective Catalytic Conjugate Addition of Dialkyl­zinc Compounds

  • 3.3.1 Chiral Catalysts

  • 3.3.2 Addition to 3-Nitroacrylates

  • 3.3.3 Addition to 3-Alkyl Substituted 3-Nitroacrylates

  • 3.3.4 Addition to Nitrostyrene and 3-Nitroacrolein Dimethyl­acetal

  • 4 Synthesis of β2-Homoaminoacids

  • 5 Conclusions

1

Present address: Oklahoma State University, Department of Chemistry, Stillwater, OK 74078, USA.

27

Synthesized from trimethylsilylmethyllithium [(TMSM)Li] and the corresponding iodide. See also ref. [15] .

34

The data of (P,S,S)-L1 have been confirmed (private communications) by Prof. A. Alexakis, University of Geneva, Switzerland {[α]D +8.3 (c = 0.75, CHCl3)} and Prof. N. Krause, University of Dortmund, Germany {[α]D +10.5 (c = 0.75, CHCl3)}.