Copper-Catalyzed Intramolecular Alkoxylation of Purine Nucleosides: One-Step Synthesis of 5′-O,8-Cyclopurine Nucleosides

Abstract

A novel copper-catalyzed intramolecular dehydrogenative alkoxylation of purine nucleosides has been developed successfully, providing the 5'-O,8-cyclopurine nucleosides in one-step with a yield up to 90%. The method, which utilized an inexpensive CuCl catalyst and a di-tert-butyl peroxide (DTBP) oxidant was suitable in a broad substrate scope and proceeded well even in gram scale.

Nucleophilic C–H Etherification of Heteroarenes Enabled by Base-Catalyzed Halogen Transfer

“…We first targeted the 2-selective C–H etherification of 1,3-azoles for development, as there is currently no general protocol for this coupling process. , Optimization of a model reaction between thiazole ( 1 ) and 2-ethyl-1-hexanol ( 2 ) is shown in Scheme a using KO- t -Bu as base . We began by examining 2-bromothiophenes as potential oxidants, which are inert toward nucleophilic aromatic substitution .…”

“…4,5-Dimethylthiazole (13) undergoes 2-etherification without competing methyl oxidation. Substrates with halogen substituents (15,18) and additional aryl groups (15,17,21) favor 1,3-azole etherification over potential substitution or unselective halogenation side reactions.…”

Silver-Mediated Methoxylation of Aryl C(sp2)–H Bonds Directing by DMEDA

“…While MgSO 4 were used as an additive, the yield was improved to 78% (Entry 14, Isolated yield 71%). However, no obvious improvement could be observed when other additives were added to this system (Entry [15][16][17][18][19]. This may due to the high binding energy of Ag(3d 5/2 ) states for AgSO 4 , a Ag(II) compuond [39].…”

“…Compared to the traditional method for carbon-oxygen bond coupling [3][4][5][6], transition metal catalyzed C-H alkoxylation with alcohols has received much attention in recent decades in terms of atom and step economy [7][8][9][10]. However, direct C-H bond alkoxylation has been mostly limited to a palladium- [11][12][13][14][15] or copper-catalyzed system [16][17][18][19][20] which are both more biological toxicity metals. Recently, the first-row transition metals such as iron, cobalt, and nickel for C-H alkoxylation, have attracted more attention owing to low biological toxicity as well as low cost [21][22][23][24][25].…”

Synthesis of 1,1‐Disubstituted N‐Acyl Tetrahydroisoquinolines from Enamides by Cascade Radical Addition and Cyclization

“…Although the detailed reaction mechanism still remains to be clarified, a proposed radical reaction pathway is shown in Scheme . With the aid of [Cu] I , the benzylic H atom of methylarene was abstracted by DTBP to generate benzyl radical, and [Cu] I was oxidized to [Cu] II . Intermolecular addition of benzyl radical to substrate 1a gave the intermediate A , which underwent sequential intramolecular cyclization to produce intermediate B .…”