Thiol-Catalyzed Radical Decyanation of Aliphatic Nitriles with Sodium Borohydride

Single-Electron Reduction of "Push-Pull" C-C Single Bond and Decyanation Using Tertiary Amines as the Organic Electron Donor

Using commercially available tertiary amines as an organic electron donor (OED), the reduction of "push-pull" C-C single bond and reductive decyanation of tetrahydroisoquinolines were realized. These reactions exhibited higher reaction efficiency and better functional group tolerance compared with those of metallic reductants, and the mechanistic study indicated that a radical intermediate was involved in the reduction of the C-C single bond, which provides a new way to the OED-enabled mild reduction.

Selective Defluoroalkylation and Hydrodefluorination of Trifluoromethyl Groups Photocatalyzed by Dihydroacridine Derivatives

The selective functionalization of trifluoromethyl groups through C-F cleavage poses a significant challenge due to the high bond energy of the C(sp3)-F bonds. Herein, we present dihydroacridine derivatives as photocatalysts that can functionalize the C-F bond of trifluoromethyl groups with various alkenes under mild conditions. Mechanistic studies and DFT calculations revealed that upon irradiation, the dihydroacridine derivatives exhibit high reducibility and function as photocatalysts for reductive defluorination. This process involves a sequential single-electron transfer mechanism. This research provides valuable insights into the properties of dihydroacridine derivatives as photocatalysts, highlighting the importance of maintaining a planar conformation and a large conjugated system for optimal catalytic activity. These findings facilitate the efficient catalytic reduction of inert chemical bonds.

Starting from Styrene: A Unified Protocol for Hydrotrifluoromethylation of Diversified Alkenes

In contrast with unactivated alkenes, the corresponding hydrotrifluoromethylation of styrene has remained challenging due to the strong propensity of styrene for oligomerization and polymerization. On the basis of our newly developed trifluoromethylation reagent, TFSP, herein we present a general method for the hydrotrifluoromethylation of styrene under photoredox catalysis. The substrate scope was further extended to unactivated alkenes, acrylates, acrylamides, and vinyl-heteroatom-substituted alkenes. The tunability of this method was showcased via the relevant deprotonative trifluoromethylation and trifluoromethyltrifluoroethoxylation reactions.

Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant

Ethanol, as an environmentally friendly and renewable reagent, was applied as a hydride donor to convert C–CN to C–H bonds in this nickel-catalyzed protocol.

Photocatalyzed intermolecular amination for the synthesis of hydrazonamides

A photocatalyzed intermolecular amination strategy for the synthesis of hydrazonamides is reported by a multi-component reaction of β-ketonitriles with N,N-disubstituted hydrazines.

Hydrodecyanation of Secondary Alkyl Nitriles and Malononitriles to Alkanes using DiMeImd-BH3

The decyanation of secondary aliphatic nitriles and the 2-fold decyanation of malononitriles leading to alkanes in the presence of 1,3-dimethylimidazol-2-ylidene borane (diMeImd-BH₃) are reported. These reactions proceed via a radical mechanism that involves the addition of a borane radical to the nitrile to form an iminyl radical, followed by cleavage of a carbon-carbon bond. Theoretical calculations suggest that the β-cleavage of these iminyl radicals, which affords NHC-BH₂CN and the corresponding alkyl radicals, is the rate-determining step in this reaction.

Titanium(III)-Catalyzed Reductive Decyanation of Geminal Dinitriles by a Non-Free-Radical Mechanism

A titanium-catalyzed mono-decyanation of geminal dinitriles is reported. The reaction proceeds under mild conditions, tolerates numerous functional groups, and can be applied to quaternary malononitriles. A corresponding desulfonylation is demonstrated as well. Mechanistic experiments support a catalyst-controlled cleavage without the formation of free radicals, which is in sharp contrast to traditional stoichiometric radical decyanations. The involvement of two TiIII species in the C-C cleavage is proposed, and the beneficial role of added ZnCl2 and 2,4,6-collidine hydrochloride is investigated.

Reductive Cleavage of Unactivated Carbon-Cyano Bonds under Ammonia-Free Birch Conditions

A general protocol for the reductive cleavage of unactivated carbon-cyano bonds in aliphatic nitriles has been achieved under single-electron-transfer conditions using Na/15-crown-5/H₂O. Electron is supplied by the electride derived from bench-stable sodium dispersions and recoverable 15-crown-5. H₂O provides the proton source and suppresses the reduction of aromatic moieties. Compared with the Na/NH₃ electride system generated under traditional Birch conditions, this ammonia-free electride system is more practical and features better reactivity and chemoselectivity for the decyanations of a broad range of aliphatic nitriles.

Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source

The general dehalogenation of alkyl halides with zinc using D₂O or H₂O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.

Intermolecular Phosphite-Mediated Radical Desulfurative Alkene Alkylation Using Thiols

We report herein the development of a S atom transfer process using triethyl phosphite as the S atom acceptor that allows thiols to serve as precursors of C-centered radicals. A range of functionalized and electronically unbiased alkenes including those containing common heteroatom-based functional groups readily participate in this reductive coupling. This process is driven by the exchange of relatively weak S-H and C-S bonds of aliphatic thiols for C-H, C-C, and S-P bonds of the products formed.

Cleavage of carbon–carbon bonds by radical reactions

This review provides insights into the in situ generated radicals triggered carbon–carbon bond cleavage reactions.