Direct Synthesis of Secondary Benzylic Alcohols Enabled by Photoredox/Ni Dual-Catalyzed Cross-Coupling

An operationally simple, mild, redox-neutral method for the cross-coupling of α-hydroxy­alkyl­trifluoro­borates is reported. Utilizing an Ir photocatalyst, α-hydroxyalkyl radicals are generated from the single-electron oxidation of the trifluoroborates, and these radicals are subsequently engaged in a nickel-catalyzed C–C bond-forming reaction with aryl halides. The process is highly selective, functional group tolerant, and step economical, which allows the direct synthesis of secondary benzylic alcohol motifs

Synthesis of Adjacent Quaternary Stereocenters by Catalytic Asymmetric Allylboration

Allylboration of ketones with γ-disubstituted allyl­boronic acids is performed in the presence of chiral BINOL derivatives. The reaction is suitable for single-step creation of adjacent quaternary stereo­centers with high selectivity. We show that, with an appropriate choice of the chiral catalyst and the stereo­isomeric prenyl substrate, full control of the stereo- and enantio­selectivity is possible in the reaction

Selective Formation of Adjacent Stereocenters by Allylboration of Ketones under Mild Neutral Conditions

Allylboronic acids readily react with a broad variety of ketones, affording homoallylic alcohols with adjacent quaternary and tertiary stereocenters. The reaction proceeds with very high anti stereoselectivity even if the substituents of the keto group have a similar size. α-Keto acids react with syn stereoselectivity probably due to the formation of acyl boronate intermediates. The allylation reactions proceed without added acids/bases under mild conditions. Because of this, many functionalities are tolerated even with in situ generated allylboronic acids

Stereoselective Intermolecular Allylic C–H Trifluoroacetoxylation of Functionalized Alkenes

Pd-catalyzed allylic C–H trifluoroacetoxylation of substituted alkenes was performed using PhI­(OCOCF₃)₂ as the oxidant and acyloxy source. Trifluoroacetoxylation of monosubstituted cyclopentenes and cyclohexenes proceeds with excellent regio- and diastereoselectivity. Studies with one of the possible (η³-allyl)­Pd­(II) intermediates suggest that the reaction proceeds via stereoselective formation of Pd­(IV) intermediates and subsequent stereo- and regioselective reductive elimination of the product