Dearomatization of 3-Nitroindoles Enabled Using Palladium-Catalyzed Decarboxylative [4 + 2] Cycloaddition of 2-Alkylidenetrimethylene Carbonates.

A dearomatization process of 3-nitroindoles enabled using palladium-catalyzed decarboxylative [4 + 2] cycloaddition of either 2-alkylidenetrimethylene carbonates or 2-(hydroxymethyl)-3-arylallyl carbonates has been developed, affording a wide range of indoline-fused tetrahydropyrans in good yields with excellent diastereoselectivities. This reaction features a wide substrate scope and mild conditions and represents the first example of the application of π-allyl palladium 1,4-[O,C]-dipole species for the dearomative cycloaddition of electron-deficient heteroarenes.

Catalytic asymmetric aromatizing inverse electron-demand [4+2] cycloaddition of 1-thioaurones and 1-azaaurones.

Using 1-thioaurones and 1-azaaurones as electron-deficient oxa-dienes, an organocatalytic asymmetric aromatizing inverse electron-demand [4+2] cycloaddition with γ-deconjugated butenolides and azlactones was developed. A wide range of optically active benzothiophene-fused δ-lactones and indole-fused δ-lactones were obtained with desirable outcomes (up to 94% yield, >99 : 1 dr and 99% ee).

Catalytic Enantioselective α-Allylation of Deconjugated Butenolides with Aza-π-allylpalladium 1,4-Dipoles: Access to Optically Pure 2-Piperidones Bearing an All-Carbon Quaternary Stereocenter.

A palladium-catalyzed enantioselective α-allylation of deconjugated butenolides with aza-π-allylpalladium 1,4-diploes, in situ generated from palladium-mediated decarboxylation of cyclic carbamates and amide-substituted acyclic carbonates, has been successfully developed. An array of enantioenriched 2-piperidones bearing an all-carbon quaternary stereocenter were obtained in high yields with excellent enantioselectivities (up to 99% yield and 99% ee). The utility of this method was also showcased by a large-scale reaction and synthetic transformations of the product.

Catalytic asymmetric coupling of vinylogous species via deconjugated butenolide addition to vinylogous imines in situ generated from arylsulfonyl indoles.

An efficient catalytic asymmetric coupling of vinylogous species is developed via deconjugated butenolide addition to vinylogous imines in situ generated from arylsulfonyl indoles. With quinine-derived bifunctional squaramide as the catalyst, a series of structurally diverse enantioenriched sec-alkyl-3-substituted indoles containing valuable γ,γ-disubstituted butenolide moieties and adjacent quaternary-tertiary stereocenters are obtained in synthetically viable results (up to 97% yield, 77 : 23 dr and 97% ee).

Catalytic asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols with in situ generated ortho-quinone methides for the synthesis of polysubstituted chromanes.

An efficient asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols and in situ generated ortho-quinone methides with chiral phosphoric acid as the catalyst was developed. This reaction enables the highly enantioselective synthesis of chiral polysubstituted chromanes bearing multiple contiguous stereogenic centers in excellent yields and stereoselectivities (up to 99% yield, >95 : 5 dr and >99% ee).