A chiral phosphoric acids catalyzed regio‐ and enantioselective 1,10‐conjugate addition of 2‐arylindoles to alkynyl indole imine methides formed in situ from α‐(6‐indolyl)propargylic alcohols has been developed. With the established system, organocatalytic asymmetric 3‐allenylation of indoles was realized, affording a broad scope of axially chiral tetrasubstituted allenes bearing two indole motifs in high yields with stereoselectivities. Importantly, the organocatalytic remote stereocontrolled strategy disclosed the asymmetric 3‐allenylation of indoles via 1,10‐conjugate addition for the first time.
An organocatalytic construction of axially chiral tetrasubstituted allenes featuring indole skeletons has been established. With the aid of chiral phosphoric acid, alkynyl indole imine methides were formed in situ from α-(3-indolyl)propargylic alcohols, followed by the asymmetric 1,6-conjugate addition with 2-substituted indoles, furnishing axially chiral indole-containing tetrasubstituted allenes in generally high yields and enantioselectivities.
With the aid of chiral phosphoric acid, enantioselective 1,6-addition of tryptamines to in situ formed alkynyl 7-methylene-7H-indoles from tertiary α-(7-indolyl)methanols has been established for the first time, furnishing a broad...
Conjugate addition is one of the most powerful and practical methods for the formation of carbon-carbon and carbon-heteroatom bonds in organic synthesis. Owing to the rapid development of asymmetric catalysis, significant progress has been made in the field of asymmetric conjugate addition, such as 1,4-addition and 1,6-addition. However, formidable challenge of controlling chemo-, regioand stereoselectivity arises with the extended conjugated systems. Recently, with the aid of Brønsted acids catalysis, functionalized benzyl alcohols and indolylmethanols has been successfully developed as suitable precursors of electron-deficient conjugate systems for organocatalytic remote stereocontrolled conjugate additions. This review investigates the advances in the field of organocatalytic enantioselective 1,8-conjugate addition and 1,10-conjugate addi-tion of in situ formed electron-deficient conjugate systems from functionalized alcohols, which is organized according to the substrates. 1. 2.2. Addition of propargyl aza-p-quinone methides 2.3. Addition of 6-methylene-6H-indoles 2.4. Addition of propargyl 2-methylene-2H-indoles 3.Asymmetric 1,10-Conjugate addition 3.1. Addition of heteroaryl 2-methylene-2H-indoles 4.Conclusions
With the aid of acetic acid, a 1,10-conjugate addition-mediated formal [3+3] cyclization of alkynyl indole imine methides formed in situ from α-(6-indolyl) propargylic alcohols with 1,3-dicarbonyl compounds such as 4-hydroxycoumarins...
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