Catalytic Asymmetric Ring-Opening/Cyclopropanation of Cyclic Sulfur Ylides: Construction of Sulfur-Containing Spirocyclopropyloxindoles with Three Vicinal Stereocenters.

A highly efficient asymmetric ring-opening/cyclopropanation reaction of ( E)-3-(oxyethylidene)-2-oxoindolines with 1-alkyl-3-oxotetrahydro-1 H-thiophen-1-ium salts as cyclic sulfur ylides was realized by using a chiral N, N'-dioxide/Mg(OTf)2 complex as catalyst. A range of sulfur-containing syn, anti spirocyclopropyloxindoles with three contiguous stereocenters were obtained in excellent yields with excellent dr and good ee values under mild reaction conditions. The origin of stereoselectivity was discussed.

Highly regio-, diastereo- and enantioselective deracemization of axially chiral 3-alkylideneoxindoles.

The first catalytic asymmetric dynamic resolution of unprotected racemic 3-(4-alkylcyclohexylidene)indolin-2-ones via a one-step direct vinylogous Michael reaction with chalcones was realized using a chiral N,N'-dioxide/Sc(iii) complex catalytic system. A variety of (Z)-4-alkyl-2-((3-oxo-1,3-diarylpropyl)cyclohexylidene)-indolin-2-ones with three stereogenic centers at ξ-, γ- and δ'-positions were obtained in up to 95% yield, 98% ee and 99/1 dr. A possible transition state was proposed to explain the origin of the stereoselectivity.

Highly diastereo- and enantioselective synthesis of spirooxindole-cyclohexaneamides through N,N'-dioxide/Ni(ii)-catalyzed Diels-Alder reactions.

Highly efficient asymmetric Diels-Alder reactions of methyleneindolinones with 1,3-dienylcarbamates and 1,2-dihydropyridines have been accomplished by using a chiral N,N'-dioxide/nickel(ii) complex as an efficient catalyst. New kinds of spirooxindole-cyclohexaneamides were achieved in up to 99% yield, >95 : 5 dr, and 99% ee.

Highly enantioselective construction of carbazole derivatives via [4+2] cycloaddition of silyloxyvinylindoles and ß,γ-unsaturated α-ketoesters.

A highly efficient catalytic asymmetric [4+2] cycloaddition of silyloxyvinylindoles with ß,γ-unsaturated α-ketoesters has been accomplished by an available chiral N,N'-dioxide/yttrium triflate complex. A widespread range of carbazole derivatives were obtained in 47-98% yield with 86-99% ee under mild reaction conditions.

The asymmetric synthesis of polycyclic 3-spirooxindole alkaloids via the cascade reaction of 2-isocyanoethylindoles.

A highly enantioselective dearomative cascade reaction between 2-isocyanoethylindoles and 3-alkenyl-oxindoles was realized using a chiral N,N'-dioxide-Mg(II) complex catalyst. This reaction provides a straightforward access to polycyclic 3-spirooxindoles bearing cyclopenta[b]indole units with four contiguous stereocenters in excellent yields and moderate to good stereoselectivities via a Michael/Friedel-Crafts/Mannich cascade.

A catalytic asymmetric carbonyl-ene reaction of ß,γ-unsaturated α-ketoesters with 5-methyleneoxazolines.

A catalytic asymmetric carbonyl-ene reaction of ß,γ-unsaturated α-ketoesters with 5-methyleneoxazolines was accomplished. The process was based on the utilization of a chiral N,N'-dioxide/Mg(II) catalyst, providing the desired products with excellent outcomes (up to 99% yield, >99% ee) under mild reaction conditions. Based on the experimental investigations and previous reports, a possible transition state was proposed.

Asymmetric dearomatization of indoles through a Michael/Friedel-Crafts-type cascade to construct polycyclic spiroindolines.

A highly efficient asymmetric dearomatization of indoles was realized through a cascade reaction between 2-isocyanoethylindole and alkylidene malonates catalyzed by a chiral N,N'-dioxide/Mg(II) catalyst. Fused polycyclic indolines containing three stereocenters were afforded in good yields with excellent diastereo- and enantioselectivities through a Michael/Friedel-Crafts/Mannich cascade. When 2-substituted 2-isocyanoethylindoles were used, spiroindoline derivatives were obtained through a Michael/Friedel-Crafts reaction.

Catalytic asymmetric Henry reaction of nitroalkanes and aldehydes catalyzed by a chiral N,N'-dioxide/Cu(I) complex.

An easily available N,N'-dioxide/Cu(I) complex has been developed for the catalytic asymmetric nitroaldol (Henry) reaction of aldehydes with nitroethane. Under mild reaction conditions, a series of substituted aromatic, heteroaromatic and α,ß-unsaturated aldehydes are transformed to the corresponding anti-ß-nitroalcohols in good to excellent yields (up to 99%) with moderate to good dr (up to 16.7:1 anti/syn) and high ee values (up to 97%). Besides nitroethane, nitromethane and 1-nitropropane were also employed as nucleophiles, and good enantioselectivities were obtained.

Direct asymmetric vinylogous Michael addition of 3-alkylidene oxindoles to chalcones catalyzed by a chiral N,N'-dioxide ytterbium(III) complex.

A chiral ytterbium(III)-N,N'-dioxide catalyst system has been developed for the catalytic direct asymmetric vinylogous Michael addition of 3-alkylidene oxindoles to chalcones, delivering the γ-substituted alkylideneoxindoles in high yields, enantioselectivities and good Z/E selectivities under mild reaction conditions.