This report describes the first example of palladium-catalyzed ortho-C–H glycosylation/ipso-alkenylation of aryl iodides, and the easily accessible glycosyl chlorides are used as a glycosylation reagent. The reaction is compatible with the functional groups of the substrates, and a series of C-aryl glycosides have been synthesized in good to excellent yield and with excellent diastereoselectivity. It is found that a cheap 5-norbornene-2-carbonitrile as a transient mediator can effectively promote this reaction. In addition, ipso-arylation and cyanation were also realized by the strategy.

Free radical cyclization has emerged as one of the most important reaction types, which is widely used in natural product synthesis, pharmaceutical chemistry, and materials science. This report described the combination of radical cyclization and ruthenium-catalyzed meta-selective C−H functionalization for the synthesis of arylpyrrolidone derivatives. This method exhibited the highly meta-site selectivity of the primary, secondary, and tertiary alkyl radicals formed by intramolecular addition. A wide spectrum of directing groups bearing diversified N-heterocycles performed well, including biologically active molecules. Density functional theory calculations provided a theoretical basis for the high metaselectivity and the favored reaction pathway of an intramolecular cyclization.

The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka−Heck/ C(sp 3 or sp 2 )−H activation reaction is reported here. The key step in this transformation is the activation of a δ-C−H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiropalladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp 3 )−H activation step.

We described a novel palladium-catalyzed C−H glycosylation of indole or tryptophan for a one-pot stereoselective synthesis of 2,3-diglycosylindoles and tryptophan-C-glycosides. In this strategy, the use of air and base-free and ligand-free conditions provided a highly efficient route to construct C-glycosides. The method can be applied to a wide range of cost-effective and convenient glycosyl chloride donors. Mechanistic studies indicated that the indole 2,3-diglycosylation sequence was C3 and then C2.

A novel visible-light-induced palladium-catalyzed Heck reaction for bromine sugars and aryl olefins with high regioand stereochemistry selectivity for the preparation of C-glycosyl styrene is described. This reaction takes place in one step at room temperature by using a simple and readily available starting material. This protocol can be scaled up to a wide range of glycosyl bromide donors and aryl olefin substrates. Mechanistic studies indicate that a radical addition pathway is involved.C-Glycosides, in which the glycosidic oxygen is replaced by a carbon atom, have received a great deal of attention 1 because of the crucial roles of carbohydrates in resisting metabolic degradation and biological activities. 2 Compared with N-or Oglycosides, C-glycosides show an obvious enhancement in both in vitro and in vivo stability. Despite the significant methods available for constructing C-glycosides, a stereoselective and efficient method is still challenging and lags far behind that for O-or N-glycosides. 3 Over the past few decades, synthetic methods for C-glycosides have mainly concentrated on transition-metal-catalyzed 4 cross-coupling reactions. In particular, the construction of aryl C-glycosides 5 has undergone remarkable development. In 2008, Gagnéand co-workers reported a Ni-catalyzed Negishi cross-coupling approach for the synthesis of C-alkyl and C-aryl glycosides 6 (Scheme 1, Gagne's work). Recently, an efficient and stereoselective synthesis via palladium-catalyzed C−H glycosylation of Caryl glycosides was reported by Chen and co-workers. 7 In addition, the groups of Gagne, Cossy, and Nakamura also explored nickel-, 8 cobalt-, 9 and iron-catalyzed 10 cross-coupling reactions through generation of glycosyl radical intermediates to synthesize C-aryl glycosides.Although synthetic routes for C-aryl glycosides have been widely explored, the C-glycosyl styrenes, which are versatile starting compounds for, e.g., varitriol, 11 C-glycosyl aldehydes, 12 UDP sugar derivatives, 13 pyranopyran carbohydrate amino acids, 14 and some natural products, 15 remain challenging. At the outset, an intramolecular radical cyclization strategy was applied to prepare C-glycopyranosyl styrenes. In 1991, Stork and co-workers 16 demonstrated a temporary silicon connection for constructing C-glycopyranosyl styrenes that undergo an intramolecular radical process. Soon afterward, the Beau group 17 used a similar strategy to realize samarium iodidepromoted radical cyclization for the formation of the Cglycopyranosyl bond. Over the past few years, some other