Abstract
Selective deconstructive functionalization of alkenes, other than the well-established olefin metathesis and ozonolysis, to produce densely functionalized molecular scaffolds is highly attractive but challenging. Here we report an efficient photo-mediated deconstructive germinal dihalogenation of carbon-carbon double bonds. A wide range of geminal diiodoalkanes and bromo(iodo)alkanes (>40 examples) are directly prepared from various trisubstituted alkenes, including both cyclic and acyclic olefins. This C=C cleavage is highly chemoselective and produces geminal dihalide ketones in good yields. Mechanistic investigations suggest a formation of alkyl hypoiodites from benzyl alcohols and N-iodoimides, which undergo light-induced homolytic cleavage to generate active oxygen radical species.
Highlights
Selective deconstructive functionalization of alkenes, other than the well-established olefin metathesis and ozonolysis, to produce densely functionalized molecular scaffolds is highly attractive but challenging
Common functionalization usually focuses on the installation or modification of functional groups without significantly changing the backbones of molecules
Deconstructive functionalization is attractive as it can drastically change the scaffolds of molecules to introduce new chemical space, unmask dormant functional groups, and create functionalities tethered at a predefined distance determined by ring sizes of the reactants
Summary
Selective deconstructive functionalization of alkenes, other than the well-established olefin metathesis and ozonolysis, to produce densely functionalized molecular scaffolds is highly attractive but challenging. A wide range of geminal diiodoalkanes and bromo(iodo)alkanes (>40 examples) are directly prepared from various trisubstituted alkenes, including both cyclic and acyclic olefins This C=C cleavage is highly chemoselective and produces geminal dihalide ketones in good yields. Ozonolysis and other similar oxidations with various organic and inorganic oxidants were robust to introduce two carbonyl derivatives from a single C=C bond[13,14,15,16,17] Aside from such well-established strategies, other types of deconstructive functionalization of alkenes producing densely functionalized scaffolds remain rare and challenging[18,19,20,21,22,23,24,25,26,27]. We report a direct synthetic route to geminal dihalides by photo-mediated deconstructive fragmentation of cyclic or acyclic trisubstituted alkenes (Fig. 1b)
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