Regioselective Direct Difunctionalization of Glycals: Convenient Access to 2‐Deoxyglycoconjugates Mediated by Tetra‐n‐butylammonium Iodide/Sodium Periodate

Abstract

Ac ombination of nBu 4 NI and NaIO 4 promoted the intermoleculars tereo and regioselective bisfunctionalization of glycals in am etal-free, one-pot process. The oxidative iodocaboxylation, iodoamination,a nd iodoazidation of enol ether moieties by employing carboxylic or aromatic acids, and N-nucleophiles such as 1-H-benzotriazole or NaN 3 led to glycosyl carboxylates,g lycosyla mines, and glycosyl azides, respectively.T he protocol is operationally simple, employs readily available and environmental benign reagents, and was applicable for ad iverse range of substrates to obtain stereodivergent glycoconjugatesi ny ields up to 99 %w ith diastereomeric ratios up to 100 %.

Photoswitchable Regiodivergent Azidation of Olefins with Sulfonium Iodate(I) Reagent

“…Styrenes with α-substitutions (Me or Ph) were also found to be compatible, affording the corresponding azides 44 – 46 in good yields. In particular, ( E )-β-methylstyrene can exclusively undergo Markovnikov addition to give 47 with complete trans -selectivity, attributed to the anti -opening of putative iodonium intermediate . Likewise, indene and 1,2-dihydronaphthalene followed stereoselective azidation furnishing the trans - 48 and - 49 with high dr.…”

“…Inspired by our recent interest in developing a protocol for the selective functionalization of C–C multiple bonds by employing sulfonium iodate salts, herein we present a photoswitchable approach for regiodivergent azidation of olefins under metal-free conditions. This light-controlled modular aimed for regioselective azidation will be highly advantageous in extensively studied C -heteroatom bond-forming reactions.…”

Addition of Heteroatom Radicals to endo-Glycals †

“…However, the reactions proceed Compared to 2-chloro derivatives, the corresponding iodides are even more attractive because the carbon-iodine bond can be easily reduced to 2-deoxy sugars, important building blocks for carbohydrate chemistry. Thus, various strategies have been developed by oxidation of iodides by hypervalent iodine(iii) [36,37] or sodium periodate [38] in the presence of endo-glycals 2, affording 2-iodo-2-deoxy sugars 10 in very good yields (Scheme 5). The mechanism proceeds by oxidation of iodide to iodine in the first step, formation of an iodonium ion similar to intermediate 6a (Scheme 3), and trapping of the 1-position with the carboxylate with high 1,2-trans selectivity.…”

Selective Azidooxygenation of Alkenes Enabled by Photo-induced Radical Transfer Using Aryl-λ3-azidoiodane Species

“…Inspired by these precedents and augmented with our previous studies, herein we propose a visible-light-promoted approach for the radical azidooxygenation of olefinic moiety with [bis­(azido)­iodo­(III)]­arene (PhI­(N 3 ) 2 ) under additive-free conditions (Scheme b). It is attributed to the fact that the “hypervalent I–N 3 bond” in λ 3 -azidoiodane species is significantly longer lifetime and highly polarized, which is eventually capable of generating the requisite radicals under mild visible-light irradiation .…”