Arylation de glycals catalysée par les sels de palladium: nouvelle synthèse de C-glycosides

Abstract

The arylation of peracetylated glycals catalyzed by palladium salts provides a new synthesis of C-glycosides. The title reaction is applied to several aromatic compounds, including fluoro and nitro derivatives. The regioselectivity of the reaction with respect to the aromatic nucleus is explained by the formation of an arylpalladium directly from the aromatic compound and the salt. A two-step mechanism, involving syn-addition of the arylpalladium to the glycal double bond, followed by a syn-elimination is proposed and discussed.

Enantioselective Dehydrogenative Heck Arylations of Trisubstituted Alkenes with Indoles to Construct Quaternary Stereocenters

“…2,3 Indeed, the use of electron rich multi-substituted alkenes has been restricted with issues associated with addition to a specific carbon on the alkene and overall reactivity. 4 Therefore, there is a significant need to develop systems to facilitate the direct addition of an arene to multi-substituted, electron rich alkenes. 5 …”

The Chemistry of C-Nucleosides

“…(105)(106)(107)(108)(109) This reaction was studied extensively, (105)(106)(107)(108)(109)(110)(111)(112) and the effects of protecting groups on the glycal ring on the stereochemistry of the products have been established. If the reactant ribaI contained a free OH group at the 3-position (e.g., 59, Scheme 5), a relatively sta bIe (1 adduct 60 was formed selectively, which, upon hydrogenolysis, was converted into the 2'-deoxy a-C-nucleoside 61.…”

Application of an Enyne Metathesis/Diels–Alder Cycloaddition Sequence: A New Versatile Approach to the Syntheses of C‐Aryl Glycosides and Spiro‐C‐Aryl Glycosides

“…[9][10][11][12][13] However, the limitation is that these methods require stereoselective generation of the anomeric centre. Apart from these methods, transition-metal-catalysed reactions [14] are also known for the synthesis of C-aryl glycosides though most of the cases are accompanied by b-elimination products. [13] Moreover, most of the C-aryl glycoside natural products have been found to possess a quinone moiety as a subunit and it could perhaps be speculated that the presence of the quinone moiety in these natural products may also be responsible for their significant biological activity.…”