Catalytic Asymmetric Diastereodivergent Synthesis of 2-Alkenylindoles Bearing both Axial and Central Chirality

The catalytic asymmetric diastereodivergent synthesis of axially chiral 2-alkenylindoles was established via chiral phosphoric acid-catalyzed addition reactions of C3-unsubstituted 2-alkenylindoles with o-hydroxybenzyl alcohols under different reaction conditions.Using this strategy,two series of 2-alkenylindoles bearing both axial and central chirality were synthesized in a diastereodivergent fashion with moderate to high yields and good stereoselectivities(up to 99%yield,95:5 er,>95:5 dr).Moreover,theoretical calculations were performed on the key transition states leading to different stereoisomers,which provided an in-depth understanding of the origin of the observed stereoselectivity and diastereodivergence of the products under different reaction conditions.More importantly,these 2-alkenylindoles were utilized in asymmetric catalysis as chiral organocatalysts and in medicinal chemistry for evaluation of their cytotoxicity,which demonstrated their potential applications.This study has not only established the catalytic atroposelective synthesis of axially chiral 2-alkenylindoles,but also provided an efficient strategy for catalytic asymmetric diastereodivergent construction of indole-based scaffolds bearing both axial and central chirality.

Design and catalytic atroposelective synthesis of axially chiral isochromenone-indoles

The catalytic atroposelective synthesis of axially chiral isochromenone-indoles has been established by the strategy of designing homophthalic anhydride-based indole derivatives as a new type of indole-based platform molecules for dynamic kinetic resolution.By this strategy,a wide range of axially chiral isochromenone-indoles were synthesized in high yields with excellent enantioselectivities(up to 98% yield,97% ee) via the catalytic asymmetric sulfonylation reaction of homophthalic anhydridebased indole derivatives with aryl sulfonyl chlorides under the catalysis of chiral quaternary ammonium salt as a phase-transfer catalyst.

Design and Application of m-Hydroxybenzyl Alcohols in Regioselective(3+3)Cycloadditions of 2-Indolymethanols

A new class of m-hydroxybenzyl alcohols has been designed as competent three-carbon building blocks and achieved their applica-tion in 2-indolylmethanol-involved regioselective(3+3)cycloadditions under the catalysis of Br?nsted acids.By this appoach,a series of indole-fused six-membered cycloadducts have been synthesized in overall good yields(up to 98%)with excellent regioselectivity(all>95:5 rr),thus affording a powerful method for the construction of indole-fused six-membered rings.Moreover,a catalytic asymmetric version of this(3+3)cycloaddition has been preliminarily investigated,which revealed the potential of the reaction for constructing chiral indole-fused six-membered rings in an enantioselective manner.This work not only has accomplished the first design of m-hydroxybenzyl alcohols as competent reactants,but also represents the first application of m-hydroxybenzyl alcohols as three-carbon building blocks in cycloadditions.In addition,this work provides a good example for regioselective and C3-nucleophilic(3+3)cycloadditions of 2-indolylmethanols,which will substantially enrich the chemistry of 2-indolylmethanols.

Progress in organocatalytic asymmetric (4+3) cycloadditions for the enantioselective construction of seven-membered rings

Chiral seven-membered ring systems such as seven-membered carbocycles and heterocycles are widely found in natural products and pharmaceuticals.Therefore,the catalytic enantioselective construction of such frameworks has evoked considerable interest in the field of chemistry.Among the various approaches,organocatalytic asymmetric(4+3)cycloadditions are highly effective for the enantioselective construction of seven-membered rings.Over the past two decades,substantial efforts have been devoted to this field and chemists have developed various organocatalytic asymmetric(4+3)cycloadditions.This review summarizes the progress in organocatalytic asymmetric(4+3)cycloadditions from 2003 to early 2022 and provides insights into challenging issues faced in this research field,enabling the future development of this field.

Catalytic asymmetric(3+3)cycloaddition between different 2-indolylmethanols

The catalytic asymmetric(3+3)cycloaddition between different 2-indolylmethanols has been established,in which a series of chiral indole-fused six-membered heterocycles were constructed in high yields with excellent enantioselectivities.This work not only has established the first catalytic asymmetric cycloaddition between different 2-indolylmethanols but also provided a powerful strategy for constructing enantioenriched indole-fused six-membered rings.Additionally,biological evaluation discovered some products with promising antitumor activities.Notably,theoretical calculations performed on the reaction pathway and activation mode provide an in-depth understanding of this catalytic asymmetric(3+3)cycloaddition among different 2-indolylmethanols,which will advance the understanding of the chemistry of indolylmethanols.