Asymmetric Brominative Dearomatization of 2-Naphthols Using a Cinchona Alkaloid-Based Organocatalyst.

A cinchona alkaloid-based organocatalyst enables asymmetric brominative dearomatization of 2-naphthols, providing the corresponding bromonaphthalenones with high enantioselectivities. The first metal-free reaction can accommodate a variety of functional groups and give useful frameworks bearing a Br-containing tetrasubstituted stereogenic center.

Construction of three contiguous stereocenters through amine-catalyzed asymmetric aldol reactions.

Three contiguous stereocenters were constructed by an amino acid-catalyzed asymmetric aldol reaction of α-siloxyketones with racemizable α-haloaldehydes via dynamic kinetic resolution. One-pot catalytic asymmetric synthesis of the highly functionalized products could also be accomplished by the α-bromination of simple aldehydes and the subsequent asymmetric aldol reaction.

Oxetane Intermediate during a Direct Aldol Reaction: Stereoselective [5 + 1] Annulation Affording Tetralines.

An oxetane intermediate during a direct aldol reaction was trapped with an internal aryl group to yield trans-tetraline products. The contribution of the oxetane intermediate was confirmed by 18O-isotope labeling experiments.

Synthesis of Chiral Tritylpyrrolidine Derivatives and Their Application to Asymmetric Benzoyloxylation.

An efficient synthesis of novel chiral tritylpyrrolidine derivatives has been developed. Single stereoisomers of various tritylpyrrolidine derivatives can be readily obtained through diastereomer separation by simple silica gel column chromatography. Representative compounds of this class have been shown to be efficient amine organocatalysts for asymmetric benzoyloxylation.

Enantioselective C-C Bond Formation during the Oxidation of 5-Phenylpent-2-enyl Carboxylates with Hypervalent Iodine(III).

The oxidation of (5-acyloxypent-3-enyl)benzene with hypervalent iodine(III) afforded 2-oxy-1-(oxymethyl)tetrahydronaphthalene under metal-free conditions. The acyloxy group may nucleophilically participate in the oxidative cyclization. A lactate-based chiral hypervalent iodine afforded an enantioselective variant of oxyarylation with up to 89% ee.

Metal-Free Enantioselective Oxidative Arylation of Alkenes: Hypervalent-Iodine-Promoted Oxidative C-C Bond Formation.

The enantioselective oxyarylation of (E)-6-aryl-1-silyloxylhex-3-ene was achieved using a lactate-based chiral hypervalent iodine(III) reagent in the presence of boron trifluoride diethyl etherate. The silyl ether promotes the oxidative cyclization, and enhances the enantioselectivity. In addition, the corresponding aminoarylation was achieved.

Stereoselective Formation of Substituted 1,3-Dioxolanes through a Three-Component Assembly during the Oxidation of Alkenes with Hypervalent Iodine(III).

Stereoselective formation of substituted 1,3-dioxolanes was achieved through an assembly of three components: alkene, carboxylic acid and silyl enol ether. The reaction proceeded via stereospecific generation of a 1,3-dioxolan-2-yl cation intermediate during oxidation of alkene substrates with hypervalent iodine. The stereoselective trapping of the cation intermediate with silyl enol ether completed the formation of the dioxolane product.

Asymmetric synthesis of 4,8-dihydroxyisochroman-1-one polyketide metabolites using chiral hypervalent iodine(III).

Stereoselective oxylactonization of ortho-alkenylbenzoate with chiral hypervalent iodine is applied to the asymmetric synthesis of 4-oxyisochroman-1-one polyketide metabolites including 4-hydroxymellein (1), a derivative of fusarentin 2, monocerin (3), and an epimer of monocerin epi-3.