Copper-Catalyzed Anomeric O-Arylation of Carbohydrate Derivatives at Room Temperature

Abstract

Direct and practical anomeric O-arylation of sugars lactols with substituted aryl boronic acids has been established. Using copper catalysis at room temperature under air atmosphere, the protocol proved to be general, and a variety of aryl O-glycosides have been prepared in good to excellent yields. Furthermore, this approach was extended successfully to unprotected carbohydrates including α-mannose, and demonstrated here how the interaction between carbohydrates and boronic acids can be combined with copper catalysis to achieve selective anomeric O-arylation.

C–H···Anion Interactions Assisted Addition of Water to Glycals by Sterically Hindered 2,4,6-Tri-tert-butylpyridinium Hydrochloride

“…In addition, the mismatch of the anomeric selectivities obtained in the secondary amine catalysis with the thermodynamic anomeric equilibrium ratios of hemiacetals is indicative of the kinetic origins of the products under the present catalysis. In addition, the utility of the silyl-protected hemiacetals has also been shown in the synthesis of O -aryl glycosides (Scheme ). Compounds 3j and 3g were converted to the respective O -aryl glycosides 6a and 6b via a copper-catalyzed addition of the phenylboronic acid in 89% and 92% yields, respectively.…”

Room-Temperature, Transition-Metal-Free Arylation of Alcohols with Aryl Bromides

“…Aryl alkyl ethers are prevalent structural motifs in natural products, pharmaceuticals, and agrochemicals. 1 Transition-metal-catalyzed Ullmann cross-coupling reactions of alcohols with aryl halides 2 and Chan–Lam cross-coupling reactions of alcohols with arylboronic acids 3 are well established routes to this functionality (Scheme 1a ). Recently, MacMillan and other groups independently demonstrated the photoredox nickel-catalyzed etherification of alcohols with aryl bromides/iodides 4 (Scheme 1b ).…”

“…Yield: 41.5 mg (82%); white solid; mp 145. 3 1 H NMR (400 MHz, CDCl 3 ):  = 7.57 (d, J = 8.7 Hz, 2 H), 7.00 (d, J = 8.7 Hz, 2 H), 6.92-6.84 (m, 2 H), 6.81 (d, J = 7.8 Hz, 1 H), 5.97 (s, 2 H), 5.00 (s, 2 H).…”

The Palladium-Catalyzed Glycosylation of Halotropones

“…As revealed in entries a–e of Table , simply reacting near-molar equivalents of substrates 10 and 11 with various bases in a range of solvents at elevated temperatures only led to complex product mixtures most likely resulting from the base-sensitive natures of the glucose derivative 10 (P = Ac) and the troponoid 11 . Prompted by the 1997 report of Buchwald et al, together with various more recent ones, indicating that aryl halides can be coupled with alcohols in the presence of palladium or other catalysts to afford aryl ethers, the conditions defined in entries f–h of Table were explored. Once again, however, only decomposition was observed when glucose derivative 10 (P = Ac) was involved.…”