One Product, Two Pathways: Initially Divergent Radical Reactions Reconverge To Form a Single Product in High Yield

Regioselective Synthesis of the Tetrahydrocarbazole Core of Akuammiline Alkaloids via Palladium-Catalyzed Intramolecular Arylation Reaction

Tetrahydrocarbazole is the central core for several biologically active alkaloids, and regioselective synthesis of this core is a challenging task. Herein, we report an efficient strategy for the synthesis of this core involving palladium-catalyzed intramolecular arylation reaction with excellent regioselectivity (>99%) starting from N-phenyl-bromoalkene without having any relocation of double bonds via competitive palladium-catalyzed isomerization reaction. Broad functional group tolerance and exclusive regioselectivity have been observed for meta-substituted halide substrates. Furthermore, this reaction can be scalable on the gram scale.

Atroposelective Catalytic Asymmetric Allylic Alkylation Reaction for Axially Chiral Anilides with Achiral Morita-Baylis-Hillman Carbonates

A highly efficient method to access axially chiral anilides through asymmetric allylic alkylation reaction with achiral Morita-Baylis-Hillman carbonates by using a biscinchona alkaloid catalyst was reported. Through the atroposelective approach, a broad range of axially chiral anilide products with different acyl groups, such as substituted phenyl, naphthyl, alkyl, enyl, styryl, and benzyl, were generated with very good yields, moderate to excellent cis: trans ratios, and good to excellent enantioselectivities. The reaction can be scaled up, and the synthetic utility of axially chiral anilides was proved by transformations. Moreover, the linear free energy relationship analysis was introduced to investigate the reaction.

Radical Arene Addition vs Radical Reduction: Why Organometal Hydride Chain Reactions Stop and How To Make Them Go

Nonideal kinetic chain analysis was used to examine the kinetic limitations of free-radical synthesis. Homolytic aromatic substitution (HAS: ArH + R^• → ArR + H^•) occurs in a chain-terminating side reaction to the tributyltin hydride ( SnH) reduction chain (RX + SnH + ( i^•)_cat. → RH + SnX). Kinetic modeling of premixed and slow reagent addition reactions have clarified the mechanisms of SM HAS, with the azo initiator ( iNN i) acting not only as radical source but also (as an H^• acceptor) as the redox catalyst for aromatization, and/or as a postaddition oxidant. Refractory halides and other hitherto baffling anomalies may arise from the build up of ipso (rather than ortho)-cycloadduct radicals in the steady-state radical population. The implications of these findings for "tin-free" radical chains (and emerging photoredox methods) are considered via historical and recent examples of the effects of chain-degrading radical transfer (to substrate, product, solvent, initiator, and/or reagent ligands) on the reagent's chain.

A combined density functional theory and numerical simulation investigation of levels of chirality transfer and regioselectivity for the radical cyclizations of N-methyl-, N-ethyl- and N-isopropyl-substituted ortho-halo-N-acryloylanilides

There is a high chirality transfer ratio when the N-alkyl substituent is larger in volume than isopropyl.

An "against the rules" double bank shot with diisobutylaluminum hydride to allow triple functionalization of α-cyclodextrin

Frustration leads to overreaction: when diametrically opposed regioselective debenzylation is frustrated, an unexpected double debenzylation reaction affords original tetrafunctionalized cyclodextrins in a controlled and efficient manner. A rationale of the reaction is proposed based on a kinetic study.