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1.
Angew Chem Int Ed Engl ; 59(8): 3294-3299, 2020 Feb 17.
Article in English | MEDLINE | ID: mdl-31782876

ABSTRACT

A new chiral Brønsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This "designer acid catalyst", which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2-aryl-substituted N-unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3-protonation and hydride-transfer processes. Besides, bulky C2-alkyl-substituted N-unprotected indoles are also suitable for this system.

2.
Nat Chem ; 10(1): 58-64, 2018 01.
Article in English | MEDLINE | ID: mdl-29256504

ABSTRACT

Arylation is a fundamental reaction that can be mostly fulfilled by electrophilic aromatic substitution and transition-metal-catalysed aryl functionalization. Although the azo group has been used as a directing group for many transformations via transition-metal-catalysed aryl carbon-hydrogen (C-H) bond activation, there remain significant unmet challenges in organocatalytic arylation. Here, we show that the azo group can effectively act as both a directing and activating group for organocatalytic asymmetric arylation of indoles via formal nucleophilic aromatic substitution of azobenzene derivatives. Thus, a wide range of axially chiral arylindoles have been achieved in good yields with excellent enantioselectivities by utilizing chiral phosphoric acid as catalyst. Furthermore, highly enantioenriched pyrroloindoles bearing two contiguous quaternary chiral centres have also been obtained via a cascade enantioselective formal nucleophilic aromatic substitution-cyclization process. This strategy should be useful in other related research fields and will open new avenues for organocatalytic asymmetric aryl functionalization.

3.
Angew Chem Int Ed Engl ; 56(51): 16308-16312, 2017 12 18.
Article in English | MEDLINE | ID: mdl-29105896

ABSTRACT

The first phosphoric acid catalyzed direct arylation of 2-naphthylamines with iminoquinones for the atroposelective synthesis of axially chiral biaryl amino alcohols has been developed. This reaction constitutes a highly functional-group-tolerant route for the rapid construction of enantioenriched axially chiral biaryl amino alcohols, and is a rare example of 2-naphthylamines acting as nucleophiles in an organocatalytic enantioselective transformation. Furthermore, the products, which feature various halogen atoms, provide access to structurally diverse axially chiral amino alcohols through further transformations.

4.
Org Biomol Chem ; 13(22): 6371-9, 2015 Jun 14.
Article in English | MEDLINE | ID: mdl-25974840

ABSTRACT

A cinchona alkaloid catalyzed diastereoselective and enantioselective sulfa-Michael/aldol cascade reaction between 1,4-dithiane-2,5-diol and isoindigos has been successfully developed to afford the highly congested bispirooxindole tetrahydrothiophenes with vicinal quaternary spirocenters in high yields (up to 91%), excellent diastereoselectivities (up to >20 : 1 dr), and good enantioselectivities (up to 98% ee). Some synthetic transformations of the reaction products were also studied.


Subject(s)
Cinchona Alkaloids/chemistry , Indoles/chemical synthesis , Spiro Compounds/chemical synthesis , Thiophenes/chemical synthesis , Catalysis , Crystallography, X-Ray , Indoles/chemistry , Models, Molecular , Molecular Structure , Spiro Compounds/chemistry , Stereoisomerism , Thiophenes/chemistry
5.
Org Lett ; 16(24): 6436-9, 2014 Dec 19.
Article in English | MEDLINE | ID: mdl-25494171

ABSTRACT

The first organocatalytic asymmetric synthesis of a spirooxindole skeleton incorporated with a cyclobutane moiety has been successfully developed on the basis of H-bond-directing dienamine activation. Structurally complex spirocyclobutyl oxindoles, which possess four contiguous stereocenters, including one spiro quaternary center, were obtained in good yields (up to 83%) with excellent ß,γ-regioselectivity (>19:1) and stereocontrol (up to >19:1 dr and 97% ee).


Subject(s)
Cyclobutanes/chemical synthesis , Indoles/chemical synthesis , Spiro Compounds/chemical synthesis , Catalysis , Cyclization , Cyclobutanes/chemistry , Hydrogen Bonding , Indoles/chemistry , Molecular Structure , Oxindoles , Spiro Compounds/chemistry , Stereoisomerism
6.
Chem Commun (Camb) ; 48(42): 5175-7, 2012 May 25.
Article in English | MEDLINE | ID: mdl-22517246

ABSTRACT

A stereoselective [3+2] cycloaddition of isocyanoesters to methyleneindolinones catalyzed by a quinine-based thiourea-tertiary amine has been successfully developed. Just by tuning the protecting groups on substrates, a variety of optically enriched 3,3'-pyrrolidinyl spirooxindole diastereomers could be obtained in excellent enantioselectivities (up to 99% ee).


Subject(s)
Indoles/chemistry , Pyrrolidines/chemistry , Amines/chemistry , Catalysis , Crystallography, X-Ray , Cyclization , Indoles/chemical synthesis , Molecular Conformation , Quinine/chemistry , Stereoisomerism , Thiourea/chemistry
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