Deoxygenative Transition-Metal-Promoted Reductive Coupling and Cross-Coupling of Alcohols and Epoxides

Quinoline as an Intramolecular Hydride Shuttle in the Deoxygenative Coupling Reaction of Alcohol and the Inert Methyl C(sp3)-H Bond

Reported herein is the C(sp3)-C(sp3) bond-forming at an unactivated C(sp3)-H bond via hydride transfer-initiated deoxygenative coupling reactions. Various polycyclic hydroquinolines were provided under metal-free conditions with excellent diastereoselectivity. Mechanistic study revealed that quinoline served as an intramolecular hydride shuttle to achieve the hydride abstraction and release in order. This methodology not only provides a practical strategy for direct deoxygenative coupling for the C(sp3)-C(sp3) bond-forming but also develops a new reaction type involving quinoline-enabled hydride transfer.

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Highly (E)-Selective Trisubstituted Alkene Synthesis by Low-Valent Titanium-Mediated Homolytic Cleavage of Alcohol C-O Bond

Ti-mediated homolytic C-O bond cleavage was useful for cascade radical-ionic reactions. Benzyl alcohols treated with TiCl₄(col) (col = 2,4,6-collidine) and Mn powder generated the corresponding benzyl radicals; in addition, their reaction with 2-carboxyallyl acetates and the subsequent elimination of the acetoxy group yielded α,β-unsaturated carbonyl compounds with exclusive (E)-stereoselectivity. The simplicity of the procedure and its wide substrate scope represent a solution to the drawbacks associated with the reactions.

The exploration of deoxygenation reactions for alcohols and derivatives using earth-abundant reagents

In Earth matter evolution, the deoxygenation process plays a central role as plant and animal remains, which are composed by highly oxygenated molecules, were gradually deoxygenated into hydrocarbons to give fossil fuels deep in the Earth crust. The understanding of this process is becoming crucial to the entire world and to the sustainable development of mankind. This review provides a brief summary of the extensive deoxygenation research under mild, potentially sustainable conditions. We also summarize some challenges and opportunities for potential deoxygenation reactions in the future.