Catalytic Asymmetric Dearomatization of 2,3-Disubstituted Indoles by a [4 + 2] Cycloaddition Reaction with In Situ Generated Vinylidene ortho-Quinone Methides: Access to Polycyclic Fused Indolines.

A protocol of enantioselective dearomatization of 2,3-disubstituted indoles by an organocatalytic intermolecular (4 + 2) cycloaddition reaction with in situ generated vinylidene ortho-quinone methide has been documented. A wide range of polycyclic 2,3-fused indolines containing vicinal quaternary carbon stereocenters was readily prepared in high yields and with excellent diastereo- and enantioselectivities.

Correction: Structurally divergent enantioselective synthesis of benzofuran fused azocine derivatives and spiro-cyclopentanone benzofurans enabled by sequential catalysis.

[This corrects the article DOI: 10.1039/D3SC03239F.].

Structurally divergent enantioselective synthesis of benzofuran fused azocine derivatives and spiro-cyclopentanone benzofurans enabled by sequential catalysis.

An important objective in organic synthesis and medicinal chemistry is the capacity to access structurally varied and complex molecules rapidly and affordably from easily available starting materials. Herein, a protocol for the structurally divergent synthesis of benzofuran fused azocine derivatives and spiro-cyclopentanone benzofurans has been developed via chiral bifunctional urea catalyzed reaction between aurone-derived α,ß-unsaturated imine and ynone followed by switchable divergent annulation reactions by Lewis base catalysts (DBU and PPh3) with concomitant epimerization. The skeletally diversified products were formed in high yields with high diastereo- and enantioselectivities. Computational analysis with DFT and accurate DLPNO-CCSD(T) has been employed to gain deeper insights into mechanistic intricacies and investigate the role of chiral and Lewis base catalysts in skeletal diversity.

Recent Developments in Intermolecular Cross-Rauhut-Currier Reactions.

Intermolecular cross Rauhut-Currier reactions have gained much importance in recent years. It has proved its importance through procedures involving various catalysts and resulting in complex structures with good regio- as well as stereo- selectivity. This review highlights the recent developments of these reactions, published in current years, involving both achiral and chiral catalysts to give products, having various utilities. In addition, the detailed mechanistic studies of the above-mentioned reactions are also presented.

α-Nitro-α,ß-Unsaturated Ketones: An Electrophilic Acyl Transfer Reagent in Catalytic Asymmetric Friedel-Crafts and Michael Reactions.

Herein, we introduce α-nitro-α,ß-unsaturated ketones as efficient electrophilic acyl transfer reagents, and they were employed in Friedel-Crafts as well as in Michael reactions. The desired acyl transfer products of these reactions were obtained in high yields with high to excellent enantioselectivities with t-leucine-derived squaramide catalyst under mild reaction conditions. Few applications including a synthesis of the isoxazoline motif have been demonstrated.

Diastereoselective Desymmetrization of Prochiral Cyclopentenediones via Cycloaddition Reaction with N-Phenacylbenzothiazolium Bromides.

A metal-free highly diastereoselctive [3 + 2] cycloaddition reaction has been developed between N-phenacylbenzothiazolium bromides and prochiral cyclopentene-1,3-diones. The active 1,3 dipole benzothiazolium N-phenacylide was generated in situ with the treatment of DIPEA, and the corresponding cycloaddition products were obtained in excellent yields under mild reaction conditions. The scope of the reaction is quite broad, tolerating a variety of aryl and heteroaromatic groups. A catalytic asymmetric approach was also studied preliminarily, and moderate enantioselectivity was achieved.

The catalytic asymmetric α-benzylation of aldehydes.

The first aminocatalyzed α-alkylation of α-branched aldehydes with benzyl bromides as alkylating agents has been developed. Using a sterically demanding proline derived catalyst, racemic α-branched aldehydes are reacted with alkylating agents in a DYKAT process to give the corresponding α-alkylated aldehydes with quaternary stereogenic centers in good yields and high enantioselectivities.