The first catalytic enantioselective ring-opening reaction of donor-acceptor cyclopropanes with water is described. By employing Cy-TOX/Cu(II) as catalyst, the reaction performed very well over a broad range of substrates, leading to the ring-opening products in 70-96% yields with up to 95% ee under mild conditions. The current method provides a new approach to direct access to γ-substituted GBH derivatives very efficiently. Importantly, Cu(ClO4)2·6H2O proves to serve as both a Lewis acid and a source of water, which affords a fine system to controllably release water as a nucleophile in the asymmetric catalysis.
The preparation of 2-(N-alkylamino)benzothiazoles via regioselecive N-alkylation of 2-aminobenzothiazoles has been accomplished by using benzylic alcohols as alkylating agents.
Facile and effective access for the asymmetric construction of the useful and important skeleton of the bicyclic N,O-acetals is described. Cu(II) /SaBOX could catalyze the reaction of β,γ-unsaturated α-ketoesters with cyclic enamines efficiently, thus affording the desired products in excellent yields with excellent stereoselectivities (21 examples; up to 99 % yields; up to >95:5 d.r.; and 95-99 % ee). This reaction can be well performed on gram scale, even with only 1 mol % catalyst loading. The single-crystal structures of the copper complexes lead to a good understanding of the stereo-synergistic effects of the sidearm.
A biomimetic enantioselective transamination of α-keto ester derivatives can be realized under mild conditions by using chiral quaternary ammonium arenecarboxylates in the absence of base additives. The corresponding α-amino acids can be used as versatile intermediates for further synthetic transformations that furnish chiral pyrrolidine and octahydroindolizine derivatives.
In the presence of the [Cp*IrCl 2 ] 2 /NaOH system, the direct N-alkylation of 2-aminoquinazolines and 2-aminopyrimidines with alcohols afforded the N-exosubstituted 2-(N-alkylamino)quinazolines and 2-(N-alkylamino)pyrimidines with 71-96% yields and complete regioselectivities. The protocol is highly attractive because of easily available starting materials, high atom efficiency and environmental friendliness.
Given the wide prevalence and ready
availability of both phenols
and amines, aniline synthesis through direct coupling between these
starting materials would be extremely attractive. Herein, we describe
a rhodium-catalyzed amination of phenols, which provides concise access
to diverse anilines, with water as the sole byproduct. The arenophilic
rhodium catalyst facilitates the inherently difficult keto–enol
tautomerization of phenols by means of π-coordination, allowing
for the subsequent dehydrative condensation with amines. We demonstrate
the generality of this redox-neutral catalysis by carrying out reactions
of a large array of phenols with various electronic properties and
a wide variety of primary and secondary amines. Several examples of
late-stage functionalization of structurally complex bioactive molecules,
including pharmaceuticals, further illustrate the potential broad
utility of the method.
The direct and regioselective N-alkylation of amino-azoles to the corresponding 2-N-(alkylamino)azoles using various alcohols as alkylating agents with good to excellent yields has been accomplished by an iridium complex/base system.
We developed a Ru/hemilabile-ligand-catalyzed nucleophilic aromatic substitution (S N Ar) of aryl fluorides as the limiting reagents. Significant ligand enhancement was demonstrated by the engagement of both electron-rich and neutral arenes in the S N Ar amination without using excess arenes. Preliminary mechanistic studies revealed that the nucleophilic substitution proceeds on a η 6 -complex of the Ru catalyst and the substrate, and the hemilabile ligand facilitates dissociation of products from the metal center.
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