An unsymmetrical, bifunctional chiral proton catalyst (2) has been developed to enable the highly diastereo- and enantioselective synthesis of epimerizable addition products from nitroacetic acid esters. The strategy is analogous to O'Donnell's glycine Schiff base alkylations that have been broadly applied to the synthesis of α-amino acids. In this regard, nitroacetic acid esters provide complementary products, namely, anti-α,β-diamino acids, derived from addition reactions. Products are obtained with high diastereoselection (generally 6−12:1) and enantioselection (generally >90% ee) using 5 mol% catalyst loading.
An
efficient strategy toward 4-arylquinolines and 4-arylpyrimidines from
readily available precursors is described. Oxidative annulation promoted
by K2S2O8 involving anilines, aryl
ketones, and DMSO as a methine (CH−) equivalent leads
to 4-arylquinolines via a cascade that entails generation of a sulfenium
ion, subsequent C–N and C–C bond formations, and cyclization.
The application of this strategy to the activation of acetophenone–formamide
conjugates toward the synthesis of 4-arylpyrimidines is also described.
Metal halide perovskites (MHPs) have recently emerged as an ideal semiconductor for photovoltaic application. Much of the advantageous properties of perovskite is dominated by its large charge carrier mobility (μ)...
Highly diastereo- and enantioselective additions of substituted alpha-nitroesters to imines have been developed. High diastereoselection relies on the finding that the combination of chiral proton catalyst 2b and alpha-nitro aryl esters bearing 2,6-disubstitution combine to raise substrate-controlled diastereoselection to >20:1 in favor of the syn diastereomer. Furthermore, the chiral catalyst provides enantioselection to the 99% level through control of the addition step in which the azomethine pi-faces are differentiated. The bifunctional chiral protic acid catalyst enables these reactions to proceed without separate preactivation of either substrate, leading to a straightforward synthetic protocol for the formation of alpha,beta-diamino phenyl alanine derivatives.
A [3 + 2] cycloaddition approach to the 3-hydroxy-3-alkyl oxindole scaffold is described. Isoxazolines obtained by cycloaddition of nitrile oxide 3 with 3-methylene oxindoles were elaborated to 3-hydroxy-3-cyanomethyl oxindoles employing a one-pot protocol en route to the pyrrolidinoindoline moiety which is found in many natural products. The total syntheses of alkaloids (±)-alline and (±)-CPC-1 were achieved using this methodology.
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