Development, mechanism, and scope of the palladium-catalyzed enantioselective allene diboration
In the presence of a chiral phosphoramidite ligand, the palladium-catalyzed diboration of allenes can be executed with high enantioselectivity. This reaction provides high levels of selectivity with a range of aromatic and aliphatic allene substrates. Iso
Pd-catalyzed enantioselective diboration of prochiral allenes provides adducts which participate in highly selective allylation reactions with primary imines. The allylation product is a vinyl boronate which may be oxidized to give nonracemic Mannich prod
Sleber, Joshua D.,Morken, James P.
p. 74 - 75
(2007/10/03)
Modular asymmetric synthesis of 1,2-diols by single-pot allene diboration/hydroboration/cross-coupling
Chiral allyl vinyl boronates are generated by catalytic enantioselective diboration of prochiral allenes. They may then be reacted, in situ, with a hydroborating reagent to form a novel triboron intermediate. The least hindered and most reactive C-B bond
(Chemical Equation Presented) Palladium-catalyzed enantioselective diboration of prochiral allenes generates a reactive chiral allylboron intermediate which is a versatile reagent for the allylation of carbonyls. Experiments that improve the enantioselectivity of this process, examine the substrate scope, and are directed toward functionalization of the allylation intermediate are described.
Woodward, Angela R.,Burks, Heather E.,Chan, Louis M.,Morken, James P.
p. 5505 - 5507
(2007/10/03)
Palladium-catalyzed enantioselective diboration of prochiral allenes
Pd-catalyzed diboration of prochiral allenes occurs exclusively at the internal position and is remarkably accelerated in the presence of Lewis basic ligand structures. On the basis of preliminary observations, a chiral ligand was employed, and the enantiomeric excess of a variety of diboration products was found to be in the range of 86-92% ee. The chiral diboron reaction products should be useful in organic synthesis, and preliminary experiments suggest that they may participate in allylation reactions with a high level of chirality transfer. Copyright
Pelz, Nicholas F.,Woodward, Angela R.,Burks, Heather E.,Sieber, Joshua D.,Morken, James P.
p. 16328 - 16329
(2007/10/03)
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