Asymmetric functionalization of aromatic CH bonds of N,N‐disubstituted anilines with diazo compounds and imines is reported for the efficient construction of α,α‐diaryl benzylic quaternary ...stereocenters in good yields with high diastereoselectivities and excellent enantioselectivities. This RhII/chiral phosphoric acid cocatalyzed transformation is proposed to proceed through a metal‐carbene‐induced zwitterionic intermediate which undergoes electrophilic trapping. To the best of our knowledge, this is the first asymmetric example of metal carbene‐induced intermolecular functionalization of aryl CH bonds.
Caught in a trap: The title reaction of N,N‐disubstituted anilines with diazo compounds and imines is reported for the efficient construction of α,α‐diaryl benzylic quaternary stereocenters in good yields with high diastereoselectivities and excellent enantioselectivities. Efficient electrophilic trapping of the metal‐carbene‐induced zwitterionic intermediate is crucial for the enantiocontrol under RhII/chiral phosphoric acid (PPA) co‐catalysis.
Enantioselective α-aminomethylation of carbonyl compounds constitutes a powerful protocol for introducing aminomethyl groups to simple organic molecules. However, current strategies rely on ...nucleophile-based enantioselective activation with inherently activated substrates only, and enantioselective protocol based on the activation of in situ-generated unstable formaldimines remains elusive, probably owing to their unstable nature and the lack of steric environment for efficient stereocontrols. Here, based on a rhodium/chiral phosphoric acid cooperative catalysis, we achieved an enantioselective three-component reaction of α-diazo ketones with alcohols and 1,3,5-triazines. A dual hydrogen bonding between the chiral phosphoric acid catalyst and two distinct active intermediates was proposed to be crucial for the efficient electrophile-based enantiocontrol. A series of chiral β-amino-α-hydroxy ketones including those derived from simple aliphatic alcohols, allylic alcohol, propargyl alcohol, complicated natural alcohols and water could all be prepared in high efficiency and enantioselectivity.
An enantioselective Rh(II)/chiral phosphoric acid co-catalyzed three-component reaction via trapping of oxonium ylides with 3-hydroxyisoindolinones by a formal SN1 pathway is described. This ...reaction allows for the efficient synthesis of isoindolinone derivatives with two contiguous quaternary stereogenic centers in high yields (up to 93%) with excellent enantioselectivities and moderate diastereoselectivities under mild reaction conditions.
Homogeneous gold catalysis has demonstrated the preponderant capability of realizing a broad range of synthetically versatile alkyne functionalization over the last two decades. Though catalytic ...asymmetric alkyne transformation has focused on the principle of using gold catalysts either associated with chiral phosphine ligand or combined with chiral counterion, a variety of breakthroughs have been reported with the application of gold-complex and chiral organocatalyst cooperative catalysis strategy, which could enable the challenging transformations that cannot be realized by mono-catalysis with excellent stereoselectivity. This review will cover two general protocols in this field, including relay catalysis and synergistic catalysis, with emphasis on the detailed cooperative catalysts models to illustrate the roles of the two catalysts and highlight the potential synthetic opportunities offered by asymmetric cooperative catalysis.
This review will cover two general protocols in gold-complex and chiral organocatalyst cooperative catalysis for asymmetric alkyne functionalization, including relay catalysis and synergistic catalysis, with emphasis on the detailed cooperative catalysis patterns for the asymmetric induction to illustrated the roles of the two catalysts. Display omitted
Chemical bond cleavage and reconstruction are common processes in traditional rearrangement reactions. In contrast, the process that involves bond cleavage, fragment modification and then ...reconstruction of the modified fragment provides an efficient way to build structurally diversified molecules. Here, we report a palladium(II)/chiral phosphoric acid catalysed three-component reaction of aryldiazoacetates, enamines and imines to afford α-amino-δ-oxo pentanoic acid derivatives in good yields with excellent diastereoselectivities and high enantioselectivities. The stereoselective reaction went through a unique process that involves cleavage of a C-N bond, modification of the resulting amino fragment and selective reassembly of the modified fragment. This innovative multi-component process represents a highly efficient way to build structurally diversified polyfunctional molecules in an atom and step economic fashion. A keto-iminium is proposed as a key intermediate and a chiral palladium/phosphate complex is proposed as an active catalyst.
We describe a facile strategy for building enantioenriched fluoroalkyl-substituted syn-diamines by the asymmetric gem-difunctionalization of 2,2,2-trifluorodiazoethane, which could be efficiently ...converted to a series of fluoroalkyl-substituted structures. The proposed key intermediate is an ammonium ylide generated from 2,2,2-trifluorodiazoethane, and its reactivity was further explored by DFT calculations.
Reaction trio: The title reaction delivers CH functionalized pyrrole derivatives in moderate to good yields. This novel three‐component reaction provides both syn‐ and anti‐pyrrole derivatives ...having two contiguous stereocenters with good regio‐, diastereo‐, and enantioselectivity. This process represents the first highly enantioselective palladium‐carbenoid‐mediated reaction.
A sequential Rh2(OAc)4-catalyzed multicomponent reaction and CuCl2-catalyzed postcyclization process is developed to build polyfunctional cyclopentabindoles in good yields with high ...diastereoselectivities in an atom- and step-economic fashion. The key discovery in this process is the CuCl2-catalyzed intramolecular aerobic dehydrogenative Csp2–Csp2 cross-coupling of indole C2 with an enol functionality. Mechanistic studies including X-ray photoelectron spectroscopy analysis suggest that the catalytic cycle involves Cu(II) and Cu(I). This coupling reaction represents a unique example of aerobic Cu-catalyzed direct coupling of indoles with enols under mild conditions.
A Pd(II)-catalyzed formal 4+1 cycloaddition of aryl diazoacetates and aryl propargyl alcohols is reported to afford 2,5-dihydrofuran derivatives as the dominant product over other traditional ones. ...The auto-tandem catalytic process is proposed to occur via Pd(II)-catalyzed intermolecular oxonium ylide formation and subsequent intramolecular trapping of the ylide with Pd(II)-activated alkynes.
Metal carbene is an active synthetic intermediate, which has shown versatile applications in synthetic chemistry. Although a variety of catalytic methods have been disclosed for the generation of ...carbene species from different precursors, there is an increasing demand for the development of efficient and practical approaches for the in-situ formation of metal carbene intermediates with structural diversity and unrevealed reactivity. Herein we report a gold-catalyzed cascade protocol for the assembly of polycarbocyclic frameworks in high yields under mild reaction conditions. Mechanistic studies indicate that the unique β-aryl gold-carbene species, generated via gold-promoted 6-endo-dig diazo-yne cyclization, is the key intermediate in this reaction, followed by a 4 + 2-cycloaddition with external alkenes. In comparison to the well-documented metal carbene cycloadditions, this carbene intermediate serves as a 4-C synthon in a cycloaddition reaction. A variety of elusive π-conjugated polycyclic hydrocarbons (CPHs) with multiple substituents are readily accessible from the initially generated products by a mild oxidation procedure.
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