Catalytic Asymmetric Inverse-Electron-Demand Oxa-Diels-Alder Reaction of In Situ Generatedortho-Quinone Methides with 3-Methyl-2-Vinylindoles

Catalytic asymmetric substitution of ortho-hydroxybenzyl alcohols with tetronic acid-derived enamines: enantioselective synthesis of tetronic acid-derived diarylmethanes

The first catalytic asymmetric substitution of ortho-hydroxybenzyl alcohols with enamines has been established.

Organocatalytic asymmetric conjugate addition of t-butyl nitroacetate to o-quinone methides: synthesis of optically active α-nitro-β,β-diaryl-propionates

α-Nitro-β,β-diaryl-propionates were prepared with good yields and excellent enantioselectivities via asymmetric conjugate addition of t-butyl nitroacetate to in situ generated o-quinone methides.

Asymmetric synthesis of dihydrocoumarins via the organocatalytic hetero-Diels–Alder reaction of ortho-quinone methides

Asymmetric synthesis of the dihydrocoumarin skeletonviathe organocatalytic [4 + 2] cycloaddition reaction ofortho-quinone methides with azlactones.

Diastereo- and enantioselective construction of spirooxindole scaffolds through a catalytic asymmetric [3 + 3] cycloaddition

A chiral phosphoric acid-catalyzed asymmetric [3 + 3] cycloaddition of C3-substituted 2-indolylmethanols with isatin-derived azomethine ylides has been established, which afforded chiral spirooxindoles in considerable yields, moderate to good stereoselectivities.

Brønsted acid-catalyzed stereoselective [4+3] cycloadditions of ortho-hydroxybenzyl alcohols with N,N′-cyclic azomethine imines

The first [4+3] cycloaddition of ortho-hydroxybenzyl alcohols has been established to construct biologically important seven-membered heterocyclic scaffolds in good yields and excellent diastereoselectivities (up to 92% yield, most >95 : 5 dr).

Chiral phosphoric acid catalyzed enantioselective annulation of acyclic enecarbamates to in situ-generated ortho-quinone methides

The first organocatalytic asymmetric [4 + 2]-cycloaddition reaction between acyclic enecarbamates with in situ generated ortho-quinone methides has been developed using chiral phosphoric acids as catalysts.

Catalytic asymmetric chemodivergent arylative dearomatization of tryptophols

The first catalytic asymmetric arylative dearomatization of tryptophols has been established. By using quinone imine ketals as aryl group surrogates and modulating the reaction conditions, the cascade reaction of tryptophols with quinone imine ketals afforded two series of arylative dearomatization products in generally high yields, and excellent diastereo- and enantioselectivities.

Bismuth-catalyzed allylation of para-quinone methides

An efficient 1,6-allylation addition of para-quinone methides with allylboronic acid pinacol ester was developed with 0.5–5 mol% bismuth(iii) triflate.

Asymmetric synthesis of chromene skeletons via organocatalytic domino reactions of in situ generated ortho-quinone methide with malononitrile and β-functionalized ketone

Enantioselective organocatalytic domino reactions of in situ generated ortho-quinone methides with malononitrile and β-functionalized ketones have been developed. This strategy could generate various chiral chromenes in high yields and stereoselectivities.

Catalytic asymmetric C2-nucleophilic substitutions of C3-substituted indoles with ortho-hydroxybenzyl alcohols

Catalytic asymmetric C2-nucleophilic substitutions of C3-substituted indoles such as tryptophols or tryptamines with ortho-hydroxybenzyl alcohols have been established, leading to the generation of triaryl methane products in generally high yields and excellent enantioselectivities.

Asymmetric Inverse-Electron-Demand Oxa-Diels-Alder Reaction of Allylic Ketones through Dienamine Catalysis

A remote β,γ-regioselective asymmetric inverse-electron-demand oxa-Diels-Alder reaction between allylic ketones and α-cyano-α,β-unsaturated ketones has been developed through induced extended dienamine catalysis of a cinchona-derived primary amine. A spectrum of densely substituted dihydropyran frameworks were efficiently produced with excellent enantioselectivity and fair to exclusive diastereoselectivity.

Chiral N,N'-Dioxide-Scandium(III) Complex-Catalyzed Asymmetric Friedel-Crafts Alkylation Reaction of ortho-Hydroxybenzyl Alcohols with C3-Substituted N-Protected Indoles

The first Lewis acid catalyzed asymmetric Friedel-Crafts alkylation reaction of ortho-hydroxybenzyl alcohols with C3-substituted indoles is described. A chiral N,N'-dioxide Sc(OTf)₃ complex served not only to promote formation of ortho-quinone methides (o-QMs) in situ but also induced the asymmetry of the reaction. This methodology enables a novel activation of ortho-hydroxybenzyl alcohols, thus affording the desired chiral diarylindol-2-ylmethanes in up to 99 % yield and 99 % ee. A range of functional groups were also tolerated under the mild reaction conditions. Moreover, this strategy gives concise access to enantioenriched indole-fused benzoxocines.

Enantioselective Construction of Tetrahydroquinolin-5-one-Based Spirooxindole Scaffold via an Organocatalytic Asymmetric Multicomponent [3 + 3] Cyclization

The first catalytic enantioselective construction of biologically important tetrahydroquinolin-5-one-based spirooxindole has been developed via a chiral cinchona alkaloid catalyzed asymmetric three-component [3 + 3] cyclization of cyclic enaminone, isatin, and malononitrile, which afforded a series of tetrahydroquinolin-5-one-based spirooxindoles in high yields and with excellent enantioselectivities (up to 99% yield, 97:3 er). This reaction could be applicable to large-scale synthesis of enantioenriched tetrahydroquinolin-5-one-based spirooxindoles. This synthetic methodology will not only provide a unique approach for the construction of chiral tetrahydroquinolin-5-one-based spirooxindole scaffolds but also increase our understanding of catalytic enantioselective multicomponent reactions.

Rhodomyrtials A and B, Two Meroterpenoids with a Triketone-Sesquiterpene-Triketone Skeleton from Rhodomyrtus tomentosa: Structural Elucidation and Biomimetic Synthesis

Rhodomyrtials A and B (1 and 2), two unprecedented triketone-sesquiterpene-triketone adducts, along with five biogenetically related intermediates, rhodomentone A (3) and tomentodiones A-D (4-7), were isolated from the leaves of Rhodomyrtus tomentosa. Their structures and absolute configurations were determined by a combination of NMR spectroscopy, chemical conversion, and X-ray diffraction analysis. Compounds 1 and 2 were biomimetically synthesized via 5 and 4, respectively, rather than 3, revealing their key ordering of biosynthetic events and confirming their structural assignments. Compound 7 exhibited potent metastatic inhibitory activity against DLD-1 cells by suppressing the activation of matrix metalloproteinase (MMP)-2 and MMP-9.

The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity

The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products). Enantiomers were separated, and their configurations were determined by comparison of experimental and theoretical electronic circular dichroism spectra.

Copper-Catalyzed Borylative Aromatization of p-Quinone Methides: Enantioselective Synthesis of Dibenzylic Boronates

In this report, we establish that DM-Segphos copper(I) complexes are efficient catalysts for the enantioselective borylation of para-quinone methides. This method provides straightforward access to chiral monobenzylic and dibenzylic boronic esters, with enantiomeric ratios up to 96:4, using a commercially available chiral phosphine. Standard manipulations of the C–B bond afford a variety of chiral diaryl derivatives.

Chiral phosphoric acid catalyzed asymmetric addition of naphthols to para-quinone methides

An asymmetric addition of naphthols to in situ generated para-quinone methides catalyzed by a chiral phosphoric acid is described.

Brønsted acid-catalyzed chemodivergent reactions of ortho-mercaptobenzyl alcohols with 3-alkyl-2-vinylindoles and styrenes: [5+2] cyclization versus hydroxysulfenylation

The title reactions were established to provide efficient methods for constructing a benzoxathiepine scaffold and synthesizing β-hydroxy sulfides in good yield and excellent diastereoselectivity.