18409-21-7Relevant articles and documents
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Taber,D.F.
, p. 3513 - 3514 (1977)
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Catalytic enantioselective allylation of dienals through the intermediacy of unsaturated π-allyl complexes
Zhang, Ping,Morken, James P.
supporting information; scheme or table, p. 12550 - 12551 (2010/01/30)
(Chemical Equation Presented) The nickel-catalyzed enantioselective addition of allylboronic acid pinacol ester [allylB(pin)] to >,β,γ,δ-unsaturated aldehydes is described. This reaction results in a remarkable inversion of substrate olefin geometry, providing the Z,E-configured reaction product in good enantioselectivity and olefin stereoselectivity. The reaction appears to proceed by conversion of the dienal to an unsaturated B-allyl complex followed by reductive elimination via transition state II. Enantioselectivities range from 73-94% ee for a range of δ-substituted dienals when chiral ligand L3 is employed.
Carbenoid pathways in copper-catalyzed intramolecular cyclopropanations of phenyliodonium ylides
Mueller, Paul,Bolea, Christelle
, p. 1093 - 1111 (2007/10/03)
The enantioselectivity of the copper-catalyzed intramolecular cyclopropanation of allyl diazomalonates and the corresponding phenyliodonium ylides was investigated with a series of chiral, non-racemic ligands. The reaction of 6b in the presence of the bis[dihydrooxazole] ligand Xa in refluxing 1,2-dichloroethane proceeded to 8b with an enantiomer excess (ee) of up to 72% under optimized conditions. In contrast, 8b resulting from reaction of ylide 7b with the same ligand, but in CH2Cl2 at 0°, had an ee of only 30%. With other ligands, diazomalonate 6b reacted with a lower enantioselectivity than ylide 7b, however. The intramolecular cyclopropanation of the acetoacetate-derived phenyliodonium ylide 15b afforded 16b with 68% ee with ligand Xa, but the corresponding diazo compound was unreactive when exposed to chiral copper catalysts. The observation of asymmetric induction in the Cu-catalyzed reactions of the ylides 7 and 15 is consistent with a carbenoid mechanism however, the discrepancy of the enantioselectivities observed between diazomalonate 6b and ylide 7b suggests a competing unselective pathway for cyclopropanation outside of the coordination sphere of copper.
