Enantioselective Construction of Dihydropyran-Fused Indoles through Chiral Calcium Phosphate Catalyzed Oxo-Hetero-Diels-Alder Reactions by Using 2-Oxoindolin-3-ylidenes as Heterodienes

Chiral Calcium Phosphate-Catalyzed Enantioselective Amination of 3-Aryl-2-oxindoles with Dibenzyl Azodicarboxylate

A chiral calcium phosphate-catalyzed enantioselective amination of 2-oxindoles with dibenzyl azodicarboxylate has been developed, affording the products in consistently high yields and excellent enantioselectivity. This synthetic method features low catalyst loading and a high catalytic efficiency. Moreover, the practical value of this process is well demonstrated by a scale-up experiment and a trial of catalyst recovery and reuse.

An update on the progress of cycloaddition reactions of 3-methyleneindolinones in the past decade: versatile approaches to spirooxindoles

Cycloaddition reactions are of great interest due to their potential and rapid construction of optically enriched spiro-cyclic products. 3-Methyleneindolinones have been proven to be a valuable precursor in cycloaddition reactions for the construction of diverse 3,3'-spirocyclic oxindoles. Their versatile reactivity has provided a new forum for the development of a variety of building blocks and synthetic compounds, including bioactive molecules. Herein, significant accomplishments in the cycloaddition reactions of 3-methyleneindolinones for the synthesis of spirooxindoles have been summarised and elaborated. The review is outlined according to the type of cycloaddition such as [2 + 1], [2 + 2], [3 + 2], [4 + 2] and [5 + 2] cycloaddition reactions.

Bioinspired cyclization of in situ generated γ-indolyl β,γ-unsaturated α-keto esters via an oxidative enamine process: facile approaches to pyrano[2,3-b]indoles

A bioinspired cyclization of in situ generated γ-indolyl β,γ-unsaturated α-ketoesters with an oxoammonium salt via an oxidative enamine process has been developed.

Chiral Calcium Phosphate Catalyzed Enantioselective Amination of 3-Aryl-2-benzofuranones

A 4-tert-butyl-phenyl substituted (R)-[H₈]-BINOL chiral calcium phosphate catalyzed enantioselective amination of 3-aryl-2-benzofuranones with dibenzyl azodicarboxylate is described. The catalyst loading of the reaction is 1 mol %. This transformation is facile and has a high degree atom economy, which gave products with good yields and high enantioselectivities (79% to 99%). This reaction has excellent ee and a broad substrate scope with mild reaction conditions.

Direct asymmetric N-propargylation of indoles and carbazoles catalyzed by lithium SPINOL phosphate

Catalytic asymmetric functionalization of the N–H groups of indoles and carbazoles constitutes an important but less developed class of reactions. Herein, we describe a propargylation protocol involving the use of a lithium SPINOL phosphate as the chiral catalyst and our recently developed C-alkynyl N,O-acetals as propargylating reagents. The direct asymmetric N-propargylation of indoles and carbazoles provides hitherto inaccessible N-functionalized products. Notably, the efficiency of the system allows reactions to be run at a very low catalyst loading (as low as 0.1 mol%). Mechanistic information about the titled reaction is also disclosed. This study represents an advance in the direct asymmetric functionalization of the N–H bonds of indoles and carbazoles, and additionally expands on the application of chiral alkali metal salts of chiral phosphoric acids in asymmetric catalysis.

Asymmetric functionalization of N–H bonds constitutes an important but less developed class of reactions. Here, the authors report the asymmetric direct N-propargylation of indoles and carbazoles with a lithium SPINOL phosphate as the chiral catalyst and shed light on the reaction mechanism.

Catalytic Enantioselective Diels-Alder Reactions of Benzoquinones and Vinylindoles with Chiral Magnesium Phosphate Complexes

Tetrahydrocarbazole and its derivatives have received much attention due to the prevalence of this scaffold in natural products and their use in organic synthesis. We have developed a Diels-Alder reaction of benzoquinones and 3-vinylindoles catalyzed by chiral magnesium phosphate complexes to provide tetrahydrocarbazole derivatives in excellent yields and enantioselectivities (up to >99% yield, 99% ee). This transformation features a wide substrate scope, excellent enantioselectivities, and mild conditions.

Catalytic Asymmetric Inverse-Electron-Demand Hetero-Diels-Alder Reaction of Dioxopyrrolidines with Hetero-Substituted Alkenes

A highly efficient enantioselective inverse-electron-demand hetero-Diels-Alder reaction of dioxopyrrolidines with heterosubstituted alkenes has been realized by using a N, N'-dioxide/Ni(II) complex as the catalyst. A series of chiral bicyclic dihydropyranes were generated in excellent yields, good dr, and excellent ee values. Besides, a catalytic cycle with a possible transition state was proposed.

Catalytic Asymmetric Inverse-Electron-Demand Hetero-Diels-Alder Reactions

In this review, the recent developments in catalytic asymmetric inverse-electron-demand hetero-Diels-Alder reaction, which is recognized as one of the most powerful routes to construct highly functionalized and enantioenriched six-membered heterocycles, are described. The article is organized on the basis of different kinds of electron-deficient heterodienes, including α,β-unsaturated ketones/aldehydes, o-benzoquinones, α,β-unsaturated imines, N-aryl imines, o-benzoqinone imides, and other aza-olefins.

Substrate-controlled switchable asymmetric annulations to access polyheterocyclic skeletons

Substrate-controlled switchable asymmetric annulations of Morita–Baylis–Hillman carbonates from isatins and α-cyano-α,β-unsaturated ketones catalysed by cinchona-derived tertiary amines, giving tetrahydrofuro[2′,3′:4,5]pyrano[2,3-b]indoles or spirooxindoles incorporating a cyclopentene motif, were disclosed.

Enantioselective Synthesis of Dihydropyran-Fused Indoles through [4+2] Cycloaddition between Allenoates and 3-Olefinic Oxindoles

A highly enantioselective [4+2] annulation with respect to allenoates and 3-olefinic oxindoles catalyzed by Lewis base was reported, which proved to be an efficient way to synthesize chiral dihydropyran-fused indoles. The cycloaddition products were generally obtained in high yields (up to 98%) with very good enantioselectivities (up to 94% enantiomeric excess).

The N,N′-dioxide/Ni(ii)-catalyzed asymmetric inverse-electron-demand hetero-Diels–Alder reaction of methyleneindolinones with hetero-substituted alkenes

The asymmetric inverse-electron-demand hetero-Diels–Alder reaction of methyleneindolinones with hetero-substituted alkenes catalyzed by chiral N,N′-dioxide/Ni(ii) complexes has been accomplished, affording dihydropyran-fused indoles in up to 99% yield, >95 : 5 dr and 99% ee.

Catalytic, highly enantioselective, direct amination of enecarbamates

Highly enantioselective electrophilic amination reaction of enecarbamates with dibenzylazodicarboxylate and oxygenated nucleophiles catalyzed by chiral phosphoric acids is reported. Subsequent reduction or oxidation of the resulting precursors of α-hydrazinoimines leads to 1,2-diamines or α-amino acid precursors, respectively, in excellent yields and enantioselectivities.

N,N'-dioxide/nickel(II)-catalyzed asymmetric inverse-electron-demand hetero-diels-alder reaction of β,γ-unsaturated α-ketoesters with enecarbamates

N,N'-Dioxide/nickel(II) complexes have been developed to catalyze the inverse-electron-demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketoesters with acyclic enecarbamates. After detailed screening of the reaction parameters, mild optimized reaction conditions were established, affording 3,4-dihydro-2H-pyranamines in up to 99 % yield, 99 % ee and more than 95:5 d.r. The catalytic system was also efficient for β-substituted acyclic enecarbamates, affording more challenging 2,3,4-trisubstituted 3,4-dihydro-2H-pyranamine with three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities. The reaction could be scaled up to a gram scale with no deterioration of either enantioselectivity or yield. Based on these experiments and on previous reports, a possible transition state was proposed.

The first calcium-catalysed Nazarov cyclisation

The first calcium-catalysed Nazarov cyclisation is described.