Beilstein J. Org. Chem.2008,4, No. 17, doi:10.3762/bjoc.4.17
" nucleophiles that readily undergo 1,2-addition with Michael type acceptors instead of 1,4-addition [14][15][16]. Different strategies have been employed to achieve 1,4-addition, which is still percieved to be a challenge. For instance, Yamamoto [17] and Röschenthaler [18][19] have made use of bulky aluminum
Lewis acids to protect the carbonyl of Michael acceptors and thus sucessfully transferred the trifluoromethyl anion generated from the "Ruppert-Prakash reagent" (TMS-CF3) in a 1,4-manner rather than the favored 1,2-addition. Portella et al. [20] have shown that 1,4-addition of difluoroenoxysilanes to
PDF
Graphical Abstract
Scheme 1:
Reaction mechanism for phosphine catalyzed 1,4-addition to α,β-unsaturated compounds.