Modern Lithium Carbenoid Chemistry

A Half‐Century Odyssey in the Realm of Reactive Intermediates

“…[7] Carbenoids exhibited some of the reactions of true carbenes, that is, additions to alkenes, but were not free divalent carbon species. [8] In late 1963, I undertook postdoctoral work at Columbia University with Ronald Breslow, whose brilliant early studies of the cyclopropenium ion [9] and the mechanism of thiamine catalysis [10] fostered the fields of nontraditional aromaticity and bioorganic chemistry. Breslow suggested that I attempt to prepare a derivative of tetrahedrane by the intramolecular addition of a cyclopropenylcarbene.…”

A practical guide for using lithium halocarbenoids in homologation reactions

“…These milestones still represent the key concepts in carbenoid chemistry and put the bases for the rational design and understanding of reactions involving these versatile synthetic tools. The concomitant presence of an electron-donating and electron-withdrawing substituent at the carbon center determines the so-called ambiphilicity of these reagents [ 5 , 10 ]. Thus, carbenoids display a dual reactivity ranging from nucleophilic to electrophilic [ 6 , 11 , 12 ].…”

Chemoselective Homologation–Deoxygenation Strategy Enabling the Direct Conversion of Carbonyls into (n+1)-Halomethyl-Alkanes

“…Accordingly, solid synthetic methodologies levered on different logics (e.g., radical, electrophilic, and nucleophilic) have been designed and thoroughly applied . In this sense, the introduction of metalated α-halogenated carbon species (MCR 1 R 2 Hal, i.e., the so-called carbenoid reagents) reacting under a nucleophilic or electrophilic regime (Scheme , path a), depending on the nature of the metal, has emerged as a valuable tool for delivering synthons featuring the exact degree of functionalization requested (i.e., halogen loading) . As a result, common downsides associated with the use of conceptually different approaches, such as polyhalogenations, can be conveniently skipped.…”