Hydroamination
allows for the direct access to synthetically important
amines. Controlling the selectivity of the reaction with efficient,
widely applicable, and economic catalysts remains challenging, however.
This paper reports an iron-catalyzed formal anti-Markovnikov hydroamination
and hydroamidation of allylic alcohols, which yields γ-amino
and γ-amido alcohols, respectively. Homoallylic alcohol is also
feasible. The catalytic system, consisting of a pincer Fe-PNP complex
(1–4 mol %), a weak base, and a nonpolar solvent, features
exclusive anti-Markovnikov selectivity, broad substrate scope (>70
examples), and good functional group tolerance. The reaction could
be performed at gram scale and applied to the synthesis of drug molecules
and heterocyclic compounds. When chiral substrates are used, the stereochemistry
and enantiomeric excess are retained. Further application of the chemistry
is seen in the functionalization of amino acids, natural products,
and existing drugs. Mechanistic studies suggest that the reaction
proceeds via two cooperating catalytic cycles, with the iron complex
catalyzing a dehydrogenation/hydrogenation process while the amine
substrate acts as an organocatalyst for the Michael addition step.
The palladium-catalyzed enantioselective intramolecular C-H arylation of N-(2-haloaryl)-P,P-diphenylphosphinic amides furnishes P-stereogenic phosphine oxide derivatives in 61-99% yield with 88-97% ee. The catalyst generated in situ from a TADDOL-derived phosphoramide ligand and Pd(dba)2 is optimum in terms of yield and enantioselectivities.
A general, efficient iron-catalyzed α-alkylation of nitriles with primary alcohols through a hydrogen-borrowing pathway has been developed, allowing a wide variety of alkylated nitriles to be readily accessible. Detailed mechanistic studies suggest that the reaction proceeds via an olefin intermediate with the turnover rate limited by the hydrogenation of the olefin with an iron hydride. Apart from participating in the alkylation, the nitrile is found to play an important role in promoting the formation of and stabilizing the active catalytic species.
A new Cu-catalyzed thioorganic-boronic acid desulfitative C-C bond-forming reaction involving ketene dithioacetals/ vinylogous thioesters is reported to proceed without the assistance of ligating S-pendant. Vinylogous thiolesters and tetrasubstituted olefins were prepared by this reaction in which Cu catalyst plays a dual role under aerobic conditions.
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