Chiral ionic Brønsted acid–achiral Brønsted base synergistic catalysis for asymmetric sulfa-Michael addition to nitroolefins

Abstract

Chiral Ionic Broensted Acid-Achiral Broensted Base Synergistic Catalysis for Asymmetric Sulfa-Michael Addition to Nitroolefins. -The present new method is applicable to both aromatic and aliphatic nitroolefins giving the desired addition products with excellent enantioselectivities. The catalyst system consists of 2,6-lutidine and a binaphthyl catalyst with homogeneous axial chirality. Although aromatic nitroolefins (I) require only very small amounts of catalyst (1 mol%), slightly more amounts must be used for sterically demanding and aliphatic nitroolefins (2 mol%). Pentyl derivative (Va) is the key intermediate for the first asymmetric syntheses of both optically active taurine derivative (VI) as well as substituted β-sultam (VII). -(URAGUCHI, D.; KINOSHITA, N.; NAKASHIMA, D.; OOI*, T.; Chem. Sci. 3 (2012) 11, 3161-3164,

Recent advances in C–S bond formation via C–H bond functionalization and decarboxylation

“…10 Much of the work on C-S bond formation has been devoted to direct coupling of organic halides with thiols and the addition of thiols to unsaturated C-C bonds under freeradical or metal-catalyzed conditions. 11 Approaches that have proven successful for making sulfur-containing chiral compounds with high optical purity include asymmetric sulfa-Michael addition reaction, 12 allylic sulfonation, 13 and Diels-Alder reaction. 14 Despite their usefulness in forming C-S bonds, these methods have significant limitations, requiring either the implementation of metal-ligand combination or highly pre-functionalized precursors.…”

Phosphonium Salts in Asymmetric Catalysis: A Journey in a Decade's Extensive Research Work

“…The catalyst 88b ⋅HBArF (Ar=Ph) was also found to be applicable in the sulfa‐Michael addition of thiophenol 95 to nitrostyrene 89 and formed the product with 77% yield but strictly in the presence of a base, (Table , entries 1–3) . Under the same reaction conditions, the catalyst 88a ⋅HBArF (Ar=Ph) displayed an improved yield (88%) with an enantioselectivity of 66.5%.…”

Recent Advances in Synthesis of Chiral Thioethers

“…In 2012, Ooi and co-workers reported an asymmetric SMA catalyzed by quaternary phosphorus salt catalyst with binaphthalene diamine as the skeleton, providing adducts 134 with desired results (Scheme 41). [47] Finally, the application value of this strategy was also shown by the synthesis of optically active taurine derivatives 138 and β-sumatan 140, which was an important class of sulfur compounds (Scheme 42).…”