Search

Abstract: A catalytic enantioselective desymmetrization of meso-N-(heteroarenesulfonyl)aziridines with TMSN3 using chiral Lewis acids afforded products with high enantioselectivity. As proof of the utility of this procedure, the precursor of selective κ-opioid agonist (1S,2S)-(−)-U-50,488 was synthesized. [Copyright &y& Elsevier]

Abstract: A catalytic enantioselective Mannich-type reaction of N-(2-pyridylsulfonyl)imines in the presence of chiral bis(oxazoline)s afforded the products with high enantioselectivity. Asymmetric induction was supposed to be efficiently controlled by a new chiral center on the sulfur dynamically induced through the discriminative coordination of a chiral Lewis acid to one of the sulfonyl oxygens. [Copyright &y& Elsevier]

Abstract: A catalytic enantioselective Strecker-type reaction to N-(2-pyridylsulfonyl)imines in the presence of chiral bis(oxazoline)s afforded the products with a high enantioselectivity. A dynamically induced new chiral center on the sulfur by discriminative coordination of a chiral Lewis acid to one of the sulfonyl oxygens efficiently controlled the enantioselectivity. [Copyright &y& Elsevier]

Abstract: The reaction of 1-[(2,4,6-triisopropylphenyl)sulfinyl]-2-naphthaldehyde with (trifluoromethyl)trimethylsilane using tetramethylammonium fluoride gave trifluoromethylated compounds in high yield with high diastereoselectivity. Desilylation and subsequent recrystallization yielded the enantiomerically and diastereomerically pure trifluoroethanol, which afforded chiral 1-(2-naphthyl)-2,2,2-trifluoroethanol after removal of the sulfinyl group. [Copyright &y& Elsevier]

Abstract: Enantioselective nucleophilic addition of Grignard reagents to N-(2-pyridylsulfonyl)imines in the presence of bis(oxazoline) afforded products with good enantioselectivity. Dynamically induced chirality on the sulfur by coordination of a chiral Lewis acid to a pyridyl nitrogen and one of the sulfonyl oxygens fixes the conformation of the complex and induces enantioselectivity. Since the 2-pyridylsulfonyl group can be easily removed after the addition reaction, it acts not only as a protecting group but also as an efficient stereocontroller. [Copyright &y& Elsevier]

The enantioselective reaction of the α-thio carbanion derived from 1-phenyl-1-(phenylthio)-1-(tributylstannyl)methane with 4-substituted cyclohexanones in the presence of bis(oxazoline)s gave the products as a diastereomeric mixture. Each diastereomer obtained had high optical purity. The reaction of the α-seleno carbanion derived from the bis(phenylseleno)acetal also showed high enantioselectivity. The stereospecific elimination of the isolated diastereomers on treatment with methanesulfonyl chloride and triethylamine afforded axially chiral benzylidenecyclohexanes with high enantioselectivities up to 99% ee. [Copyright &y& Elsevier]

Abstract: The observed rate enhancement for the condensation reaction between 2-phenyl benzoic acid and isopropanol mediated by fluorous Mukaiyama reagents is described. It is shown that Mukaiyama reagents bearing a fluorous tag increase the reaction rate considerably when compared to their non-fluorous tagged counterpart. Furthermore, it is observed that the longer the fluorous chain, the higher the activity of the Mukaiyama reagent. [Copyright &y& Elsevier]

Optically active β-(trimethylsilyl)ethyl sulfoxides supported on Merrifield resin were treated with LDA and subsequently with methyl cinnamate at −78°C. Thermal treatment or reaction with TBAF liberated the optically active methyl 3-phenyl-5-trimethylsilylpent-4-enoate or methyl 3-phenylpent-4-enoate, respectively, in good yields with high enantioselectivity. [Copyright &y& Elsevier]

Enantioselective intramolecular radical cyclization of benzimidazolyl iodoalkenyl and iodoalkadienyl sulfones using chiral Lewis acids gave products with good enantioselectivity. Newly formed chiral centers could be induced effectively by enantioselective coordination to one of the sulfonyl oxygens. [Copyright &y& Elsevier]

Abstract: The enantio- and diastereoselective synthesis of allenyl aryl sulfides by asymmetric lithiation of 2-alkynyl (2-hetero)aryl sulfides is described. A dynamic thermodynamic resolution by selective crystallization of the intermediate lithium complexes derived from deprotonation, applying a bis(oxazoline) ligand, was achieved to give enantioselectivities up to 85% ee. Subsequent stereospecific nickel-catalyzed cross-coupling reactions with arylzinc reagents established a versatile access to threefold carbon-substituted allenes. [Copyright &y& Elsevier]