A complementary pair of enantioselective switchable organocatalysts
作者:Guillaume De Bo、David A. Leigh、Charlie T. McTernan、Shoufeng Wang
DOI:10.1039/c7sc02462b
日期:——
A pair of enantioselective switchable bifunctional catalysts are shown to promote a range of conjugate addition reactions in up to 95:5 e.r. and 95% conversion. Each catalyst can be switched OFF using conditions that switch the other catalyst ON. Catalyst ON:OFF ratios of up to 98:2 and 1:99 were achieved, with a ratio of reaction rates of up to 16:1 between the ON and OFF states, maintained over complete
Catalyst-free synthesis of trisubstituted tetrahydrothiophenes in water via a cascade sulfa-Michael/aldol (Henry) type reaction
作者:Jian Song、Jamia Moss、Da-Cheng Yang、Zhi Guan、Yan-Hong He
DOI:10.1039/c4ra06273f
日期:——
A simple, efficient, eco-friendly and catalyst-free procedure was developed for the construction of trisubstituted tetrahydrothiophenes via sulfa-Michael/aldol (Henry) cascade reaction in water. The protocol, simply utilizing readily-available starting materials under clean reaction conditions, provided an alternative and highly attractive approach to a series of tetrahydrothiophene derivatives from a wide range of substrates in good yields (up to 93%) with excellent diastereoselectivities (up to >99 : 1).
Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes via in Situ Generated Chiral Fluoride-Catalyzed Cascade Sulfa-Michael/Aldol Reaction of 1,4-Dithiane-2,5-diol and α,β-Unsaturated Ketones
A chiral fluoride-catalyzed asymmetriccascade sulfa-Michael/aldol condensation reaction of 1,4-dithiane-2,5-diol and a series of α,β-unsaturated ketones is described to access chiral trisubstituted tetrahydrothiophene derivatives. The target products, including the spiro tetrahydrothiophene derivatives bearing a five-, six-, and seven-membered ring, were highly functionalized and showed high ee value
Stereoselectivity Enhancement During the Generation of Three Contiguous Stereocenters in Tetrahydrothiophenes
作者:Żaneta A. Mała、Mikołaj J. Janicki、Natalia H. Niedźwiecka、Robert W. Góra、Krzysztof A. Konieczny、Rafał Kowalczyk
DOI:10.1002/cctc.202001583
日期:2021.1.20
resulted in the formation of threecontiguousstereocenters in enantio‐ and diastereoselective Sulfa‐Michael/intramolecular aldol reactions cascade. Increase of the temperature to 333 K in reaction of mercaptoacetic aldehyde and various en‐ynones allowed the rise of the reaction rate while not affecting the enantioselectivity nor diastereoselectivity. Stereoselectivity was dependent on the structure
A bifunctional squaramide catalyzed sulfa-Michael/aldol cascade reaction between 1,4-dithiane-2,5-diol and chalcones with a low catalyst loading has been developed. Trisubstituted tetrahydrothiophenes with three contiguous stereogenic centers are obtained in a highly stereocontrolled manner. Additionally, a remarkable temperature effect on reaction efficiency was observed and a synthetically potential gram-synthesis was also conducted.