A redox-neutral alkyl Petasis reaction has been developed that proceeds via photoredox catalysis. A diverse set of primary, secondary, and tertiary alkyltrifluoroborates participate effectively in this reaction through a single-electron transfer mechanism, in contrast to the traditional two-electron Petasis reaction, which accommodates only unsaturated boronic acids. This protocol is ideal to diversify benzyl-type and glyoxalate-derived aldehydes, anilines, and alkyltrifluoroborates toward the rapid assembly of libraries of higher molecular complexity important in pharmaceutical and agrochemical settings.
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.
An
electrophilic, imide-based, visible-light-promoted photoredox/Ni-catalyzed
cross-coupling reaction for the synthesis of aliphatic ketones has
been developed. This protocol proceeds through N–C(O) bond
activation, made possible through the lower activation energy for
metal insertion into this bond due to delocalization of the lone pair
of electrons on the nitrogen by electron-withdrawing groups. The operationally
simple and mild cross-coupling reaction is performed at ambient temperature
and exhibits tolerance for a variety of functional groups.
Textbook revision: Allylboronic acids, which are easily prepared from allylic alcohols, react readily and selectively with ketones without Lewis acid catalysts.
The catalytic asymmetric allylboration of cyclic imines with γ,γ‐disubstituted allylboronic acids provides products with adjacent stereocenters in high yield and stereoselectivity. Various electrophiles, including 3,4‐dihydroisoquinolines and indoles, were prenylated in a fully stereodivergent fashion by switching the E/Z geometry of the allylboronate and/or the enantiomer of the BINOL catalyst. 3‐Methylindole provided products with three adjacent stereocenters with high stereoselectivity in one synthetic operation.
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