Transition-metal catalyzed cross-coupling reactions have created an epoch in modern synthetic organic chemistry, offering a variety of insights in retrosynthetic tactics to synthesize targeted complex molecules in medicine and materials-based applications. Despite numerous types of combinations between nucleophiles, electrophiles, and transition-metal catalysts available for the cross-coupling reactions, construction of covalent bonds including sp 3 -hybridized carbon(s) still remains a challenge due to the inherent diverse reactivity of the alkyl species (i.e. alkyl halides, alkyl metals) involved in the catalytic cycle. To realize this goal, the methods to leverage alkyl radicals have recently emerged. This perspective highlights and discusses recent advances on transition-metal catalyzed cross coupling reactions that engage alkyl radicals for C(sp 3 )-N and C(sp 3 )-Si bond formation with alkyl halides as well as use of carboxylic acid derivatives as surrogates of alkyl halides in decarboxylative C(sp 3 )-C(sp 2 )/C(sp 3 )/B couplings.
Among organic azides, vinyl azides have shown versatile chemical reactivities in the recent development of new synthetic methodologies mainly for nitrogen-containing molecules. This synopsis highlights and discusses recent advances on use of vinyl azides in chemical synthesis as a radical acceptor and an enamine-type nucleophile.
A method for the nucleophilic amination of methoxy arenes was established by using sodium hydride (NaH) in the presence of lithium iodide (LiI). This method offers an efficient route to benzannulated nitrogen heterocycles. Mechanistic studies showed that the reaction proceeds through an unusual concerted nucleophilic aromatic substitution.
Diastereoselective anti-aminooxygenation and anti-diamination of alkenes with amidines were enabled by hypervalent iodine(III) reagents such as PhI(OCOR)2 and PhI(NMs2)2, respectively. The present transformation offers diastereochemically pure dihydroimidazoles divergently from E- and Z-alkenes.
We report a protocol for aryl cross-coupling of electron-deficient aryl halides with electron-rich (hetero)arenes that is driven solely by violet light. This process takes advantage of formation of photo-excited state of electron-deficient aryl halides, that are reduced by electron-rich (hetero)arenes to form a pair of aryl anion and cation radicals. The resulting aryl anion radicals of aryl halides undergo mesolysis of the carbonhalogen bond to generate aryl radicals, that are coupled most likely with aryl cation radicals to afford functionalized biaryls.
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