Organocatalytic Asymmetric Michael Addition of Oxazolones to Arylsulfonyl Indoles: Facile Access to<i>syn</i>-Configured α,β-Disubstituted Tryptophan Derivatives
Enantioselective Michaeladdition of oxazolones to in situ generated vinylogous imine intermediates is reported. A series of optically active 3-alkylindole derivatives with adjacent quaternary and tertiary stereocenters was obtained. The resulting adducts can readily be converted into syn-configured α,β-disubstitutedtryptophanderivatives without compromising the stereoselectivities.
Catalytic asymmetric coupling of vinylogous species <i>via</i> deconjugated butenolide addition to vinylogous imines <i>in situ</i> generated from arylsulfonyl indoles
An efficient catalytic asymmetric coupling of vinylogous species is developed via deconjugated butenolide addition to vinylogousimines in situgeneratedfromarylsulfonylindoles. With quinine-derived bifunctional squaramide as the catalyst, a series of structurally diverse enantioenriched sec-alkyl-3-substituted indoles containing valuable γ,γ-disubstituted butenolide moieties and adjacent quaternary-tertiary
An organocatalytic asymmetric vinylogousMichaeladdition of dicyanoolefins to vinylogousimineintermediatesgenerated in situfrom arenesulfonylalkylindoles has been developed. This protocol provides an easy and convenient approach to C-3 alkyl-substituted indole derivatives with high yields (up to 93%), diastereomeric ratios (up to 99:1 dr) and enantioselectivities (up to 99% ee). The resulting
An efficient organocatalyzed enantioselective hydrophosphinylation of indole-derived vinylogous imines generated in situ from sulfonyl indoles has been developed. Using quinine-derived bifunctional thiourea as the catalyst, a wide range of structurally diverse chiral 3-(1-diphenylphosphoryl-arylmethyl)indoles were obtained with good to excellent results (up to 99% yield and 99% ee). This method represents
A concise synthesis of spiro-cyclopropane compounds from indole derivatives and sulfur ylides has been developed via a dearomatization strategy. Moreover, the spiro-cyclopropane compounds could be conveniently transformed to rearomatized indole derivatives in the presence of acids.