Diastereoselective friedel-crafts alkylation of indoles with chiral α-phenyl benzylic cations. Asymmetric synthesis of anti-1,1,2- triarylalkanes
(Chemical Equation Presented) The reactions of chiral benzyl carbocations bearing α-phenyl substituents with N-sulfonylated indoles afford 1,1,2-triarylalkanes with antiselectivities. This outcome is a reversal of facial diastereoselectivity relative to B
Chung, John Y. L.,Mancheno, Danny,Dormer, Peter G.,Variankaval, Narayan,Ball, Richard G.,Tsou, Nancy N.
supporting information; experimental part
p. 3037 - 3040
(2009/05/07)
Lewis base-catalyzed addition of trialkylaluminum compounds to epoxides
A novel concept for catalytic epoxide alkylation has been developed. Lewis bases like phosphanes, arsanes, stibanes, and sulfides were found to catalyze the alkylation of symmetrical epoxides with trialkylaluminum compounds very effectively at a 5 mol % level. Cyclic as well as acyclic epoxides were readily alkylated in good yields. In reactions with terminal epoxides a significant enhancement of rate and/or regioselectivity was noted in the Lewis base-catalyzed process. Coordination of the Lewis base to the Lewis acidic aluminum reagent was proved by 27Al and 31p NMR spectroscopy and is proposed to form a more nucleophilic alkylating agent.
Schneider, Christoph,Brauner, J?rg
p. 4445 - 4450
(2007/10/03)
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