"Bulky-Yet-Flexible" α-Diimine Palladium-Catalyzed Reductive Heck Cross-Coupling: Highly Anti-Markovnikov-Selective Hydroarylation of Alkene in Air

Transition-Metal-Free Anti-Markovnikov Hydroarylation of Alkenes with Aryl Chlorides through Consecutive Photoinduced Electron Transfer

The hydroarylation of alkenes has emerged as a powerful strategy for arene functionalization. However, aryl chlorides remain a large challenge in this type of reaction due to the chemical inertness of the C(sp2)-Cl bond and high negative reduction potential. Herein, we report an anti-Markovnikov radical hydroarylation of alkenes with aryl chlorides via visible-light photoredox catalysis. The key reactive aryl radicals can be efficiently achieved from aryl chlorides by consecutive photoinduced electron transfer. This transition-metal-free protocol features mild conditions, a wide substrate scope, and functional group tolerance, producing a diverse range of linear alkylarenes in moderate to good yields. The reaction is proposed to proceed through a radical-polar crossover pathway.

The Mizoroki-Heck reaction between in situ generated alkenes and aryl halides: cross-coupling route to substituted olefins

This review covers palladium-catalyzed typical Mizoroki-Heck cross-coupling reactions of aryl halides with in situ generated alkenes, by following a typical Heck coupling mechanism to form substituted olefins unlike direct cross-coupling of alkenes with aryl halides in Heck olefination. These reactions solve the issue of alkenes undergoing polymerization at high temperatures and increase reaction efficiency by reducing the reaction time and purification steps.

Imidazolidine Hydride Donors in Palladium-Catalyzed Alkyne Hydroarylation

Aldehyde-derived imidazolidines participate as hydride donors in intramolecular reductive Heck-type reactions. N,N′-Diphenylimidazolidines prepared from ortho-alkynyl benzaldehydes underwent regio- and stereoselective palladium-catalyzed hydroarylation followed by formal 1,5-hydride transfer and reductive elimination to afford substituted alkenes and imidazolium moieties, the latter conveniently converted in situ to ring-opened benzanilides to simplify product isolation. Internal alkynes were converted to trisubstituted alkenes via a syn hydroarylation process, while a terminal alkyne was converted to a cis alkene via a formal trans hydroarylation reaction. Benzanilide products could be converted to carboxylic acid derivatives under basic conditions, resulting in the net conversion of alkynyl aldehydes to alkenyl carboxylic acids. A styrene derivative with an attached N,N′-dimethylbenzimidazoline hydride donor was also found to undergo an analogous hydroarylation/benzimidazoline oxidation to give a diarylethane product.

Phase-transfer catalyzed Michael/ammonolysis cascade reactions of enaminones and olefinic azlactones: a new approach to structurally diverse quinoline-2,5-diones

Michael/ammonolysis cascade reactions between cyclohexane-1,3-dione-derived enaminones and olefinic azlactones via phase-transfer catalysis have been developed. This method provides rapid access to a suite of architecturally complex and diverse quinoline-2,5-diones bearing a secondary amide group at the C-3 position in moderate to excellent yields (53-94%) and with excellent diastereoselectivities (>99 : 1 dr in most cases). The achievement of a preparative-scale reaction and the diverse product derivatization that can be obtained highlight the application potential of this protocol both in academic and industrial settings. An investigation of the reaction mechanism implies that tetrabutylammonium hydroxide may be the actual catalyst during this cascade reaction.

Directed Markovnikov hydroarylation and hydroalkenylation of alkenes under nickel catalysis

We report a full account of our research on nickel-catalyzed Markovnikov-selective hydroarylation and hydroalkenylation of non-conjugated alkenes, which has yielded a toolkit of methods that proceed under mild conditions with alkenyl sulfonamide, ketone, and amide substrates. Regioselectivity is controlled through catalyst coordination to the native Lewis basic functional groups contained within these substrates. To maximize product yield, reaction conditions were fine-tuned for each substrate class, reflecting the different coordination properties of the directing functionality. Detailed kinetic and computational studies shed light on the mechanism of this family of transformations, pointing to transmetalation as the turnover-limiting step.

Native Lewis basic functional groups enable the nickel-catalyzed Markovnikov-selective hydroarylation and hydroalkenylation of unactivated alkenes with organoboron reagents.