PUB - Publikationen an der Universität Bielefeld

Symmetrical (R2Zn) or mixed diorganozinc compounds ((RZnR2)-Zn-1) 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 beta(2)-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 Diorganozine 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 beta(2)-Homoaminoacids 5 Conclusions.