Enantioselective Dearomative Research Articles

Lewis Acid-Promoted Enantioselective Dearomative Spirocyclizations of Allenes.

A chiral oxazaborolidine combined with SnCl4 has been found to promote the dearomative spirocyclization of electron-rich benzyl allenyl ketones. The reaction outcome is sensitive to the nature of activating acid, which was rationalized using hard-soft acid-base (HSAB) theory. The spirocyclic product was obtained with up to 72% ee, which is the best result reported to date for these substrates. The formation of cross-conjugated or conjugated products is readily controlled by changing the oxygen-protecting groups.

Zn‐Catalyzed Diastereo‐ and Enantioselective Dearomative [3+2] Cycloaddition Reaction of 2‐Nitroindoles and 2‐Nitrobenzothiophenes

AbstractAn efficient asymmetric dearomative [3+2] cycloaddition reaction of 2‐nitroindoles and 2‐nitrobenzothiophenes with 3‐isothiocyanato oxindoles was developed by using a chiral Zn(OTf)2/bis(oxazoline) complex as a catalyst. With the developed protocol, a range of enantioenriched complex heterocyclic compounds containing three contiguous stereocenters, one of which is spirocyclic center, could be obtained in quantitative yields with excellent diastereo‐ and enantioselectivities. The potential utility of this method was showcased by the diverse transformations of the products.magnified image

Diastereo- and Enantioselective Dearomative [3 + 2] Cycloaddition Reaction of 2-Nitrobenzofurans with 3-Isothiocyanato Oxindoles.

Enantioselective dearomative [3 + 2] cycloaddition reaction of 2-nitrobenzofurans with 3-isothiocyanato oxindoles was developed. The reaction employs a chiral bis(oxazoline)/Zn(OTf)2 catalyst, allowing a practical, straightforward access to structurally diverse spirooxindoles containing a 2,3-dihydrobenzofuran motif and three contiguous stereocenters with excellent diastereo- and enantioselectivities. The synthetic potentials of the method have been demonstrated by the scale-up experiment and transformations of the products. The preliminary mechanism was investigated with experimental observations, nonlinear effects studies, and MS experiments.

Enantioselective Dearomative Difunctionalization of Indoles by Palladium‐Catalyzed Heck/Sonogashira Sequence

AbstractPalladium‐catalyzed enantioselective dearomative arylalkynylation of N‐substituted indoles, through a Heck/Sonogashira sequence, was established using a new BINOL‐based phosphoramidite as the chiral ligand. A wide range of 2,3‐disubstituted indolines, bearing vicinal quaternary and tertiary stereocenters, were efficiently constructed in one step with excellent enantioselectivities (up to 97 % ee) and diastereoselectivities (>20:1).

Enantioselective Dearomative Difunctionalization of Indoles by Palladium-Catalyzed Heck/Sonogashira Sequence.

Palladium-catalyzed enantioselective dearomative arylalkynylation of N-substituted indoles, through a Heck/Sonogashira sequence, was established using a new BINOL-based phosphoramidite as the chiral ligand. A wide range of 2,3-disubstituted indolines, bearing vicinal quaternary and tertiary stereocenters, were efficiently constructed in one step with excellent enantioselectivities (up to 97 % ee) and diastereoselectivities (>20:1).

Enantioselective Dearomative [3+2] Cycloaddition Reactions of Benzothiazoles

AbstractA highly enantioselective dearomative [3+2] cycloaddition of benzothiazole has been successfully developed. A wide range of benzothiazoles and cyclopropane‐1,1‐dicarboxylates are suitable substrates for this reaction. The desired hydropyrrolo[2,1‐b]thiazole compounds were obtained in excellent enantioselectivity and yields (up to 97 % ee and 97 % yield). With the same catalytic system, a highly efficient kinetic resolution of 2‐substituted cyclopropane‐1,1‐dicarboxylates was also realized.

Enantioselective Dearomative [3+2] Cycloaddition Reactions of Benzothiazoles.

A highly enantioselective dearomative [3+2] cycloaddition of benzothiazole has been successfully developed. A wide range of benzothiazoles and cyclopropane-1,1-dicarboxylates are suitable substrates for this reaction. The desired hydropyrrolo[2,1-b]thiazole compounds were obtained in excellent enantioselectivity and yields (up to 97 % ee and 97 % yield). With the same catalytic system, a highly efficient kinetic resolution of 2-substituted cyclopropane-1,1-dicarboxylates was also realized.

Enantioselective Dearomative Arylation of Isoquinolines

The C1-substituted tetrahydroisoquinolines and 1,2-dihydroisoquinoline constitute an important group and are interesting structural motifs found in many natural products and pharmaceuticals. In this context, a phosphoric-acid-catalyzed enantioselective dearomative arylation of isoquinolines was realized, providing the chiral dihydroisoquinolines with indole substituents at the C1-position in good results (up to >99% yield and 97% ee). The reaction features mild reaction conditions and operational simplicity, which make it an attractive approach to the discovery of biologically interesting α-indolisoquinolines.

ChemInform Abstract: Enantioselective Dearomative [3 + 2] Cycloadditions of Indoles with Azomethine Ylides Derived from Alanine Imino Esters.

Catalytic, enantioselective [3 + 2] cycloadditions of azomethine ylides derived from alanine imino esters with 3-nitroindoles are reported. The dearomative cycloaddition reactions occur in the presence of a catalyst generated in situ from Cu(OTf)2 and (R)-Difluorphos to form exo′-pyrroloindoline cycloadducts and establish four contiguous stereogenic centers, two of which are fully substituted. The exo′-pyrroloindoline products are formed in moderate-to-good yields (39–85%) with high diastereoselectivities (up to 98 : 1 : 1 dr) and enantioselectivities (up to 96% ee).

Palladium-Catalyzed Enantioselective Dearomative Cyclization of Phenols

Key words palladium - dearomative cyclization - terpenes - steroids