Pradhan P, Moktan S, Biswas A, Das A, Lenka R, Kancharla PK. Triple Role of Proton Sponge (DMAN) in the Palladium-Catalyzed Direct Stereoselective Synthesis of
C-Aryl Glycosides from Glycals.
Org Lett 2024;
26:3563-3568. [PMID:
38652887 DOI:
10.1021/acs.orglett.4c00997]
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Abstract
The triple role of 1,8-bis(dimethylamino)naphthalene (proton sponge) as a reductant, ligand precursor, and organic base in the palladium-catalyzed Heck-type coupling reaction of glycals with aryl iodides affords the rapid and stereoselective synthesis of 2',3'-unsaturated α-C-aryl glycosides in excellent yields. The role of the proton sponge in reducing palladium(II) to (0) has been studied using cyclic voltammetry, UV-vis, HRMS, and other spectroscopic techniques. This is the first example of a palladium proton sponge complex utilized in coupling reactions. The method is observed to be tolerant of various functional groups, as demonstrated by the huge substrate scope. Moreover, the 2',3'-unsaturated α-C-aryl glycosides were also converted to 3-keto-β-C-glycosides under sterically hindered pyridinium salt catalysis via a ring-opening and -closing mechanism.
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