200013-10-1Relevant academic research and scientific papers
Extremely Efficient Chiral Induction in Conjugate Additions of p-Tolyl α-Lithio-β-(trimethylsilyl)ethyl Sulfoxide and Subsequent Electrophilic Trapping Reactions
Nakamura, Shuichi,Watanabe, Yoshihiko,Toru, Takeshi
, p. 1758 - 1766 (2007/10/03)
Reaction of p-tolyl α-lithio-β-(trimethylsilyl)ethyl sulfoxide with α,β-unsaturated esters gave the conjugate addition products as a single diastereomer. The intermediate enolates were subsequently trapped with various alkyl halides or aldehydes to give the products with extremely high stereoselectivity. The reaction with α,β-unsaturated ketones also proceeded with high diastereoselectivity. Protolysis of the enolates derived from the α-methyl-α,β-unsaturated esters gave the products with high stereoselectivity. The stereo- and regioselective elimination of the sulfinyl group gave chiral homoallylic carboxylates.
Transition-metal-catalyzed carbenoid reactions of sulfonium ylides
Mueller, Paul,Fernandez, Daniel,Nury, Patrice,Rossier, Jean-Claude
, p. 935 - 945 (2007/10/03)
Olefins undergo cyclopropanation with diphenylsulfonium (ethoxycarbonyl)methylide (=diphenyl-sulfonium 2-ethoxy-2-oxoethylide; 3a) in the presence of chiral Cu(I) or Rh(II) catalysis, trans/cis Ratios and ee's of the cyclopropanes 6 obtained with this ylide in the presence of a chiral Cu(I) catalyst 7 are identical with those obtained with ethyl diazoacetate (4). In the case of catalysis with Rh(II), the trans/cis ratios of the cyclopropanes as well as the enantioselectivity change slightly upon going from the ylide 3a to diazoacetate 4.
