Asymmetric addition of arylboronic acids to 2H-chromenes proceeded in the presence of a hydroxorhodium/chiral diene catalyst to give 3-arylchromanes in high yields with high enantioselectivity. The reaction involves 1,4-Rh shift before protonation to release the addition product and to regenerate the hydroxorhodium species.
Acid-catalyzed intramolecular Friedel–Crafts cyclization of optically active α-hydroxy-α-alkenylsilanes possessing a benzene ring (>99% ee) with TMSOTf as a Lewis acid gave enantio-enriched tetrahydronaphthalenes (up to 98% ee). The silyl group attached to the chiral carbon played a crucial role in the chirality transfer.
Diastereoselective direct hydroarylation of glycals with aromatic compounds was realized by use of an iridium/binap catalyst, giving the corresponding C-glycosyl compounds in high yields. The use of binap with the different absolute configuration enabled the stereoselective synthesis of α- or β-C-glycosyl arenes irrespective of the chirality of the glycals. The method showing the high functional group tolerance provides an atom-economical access to C-glycosyl arenes by way of C–H bond activation
A hydroxoiridium/cod complex efficiently catalyzed hydroarylation of conjugated dienes with arenes bearing an acidic N–H bond as a directing group, which can form an amidoiridium species as an active intermediate for C–H activation. A π-allyliridium(III) complex was isolated as a key intermediate leading to the addition product.