Visible-Light-Induced Carbo-2-pyridylation of Electron-Deficient Alkenes with Pyridinium Salts.

A simple and practical visible-light-induced carbo-2-pyridylation of electron-deficient alkenes with readily available N-benzoylmethylpyridinium bromides is reported. More than 40 examples are presented and proceed in greater than 80 % yield (on average) with excellent regio- and diastereoselectivities.

P(O)R2-directed Pd-catalyzed C-H functionalization of biaryl derivatives to synthesize chiral phosphorous ligands.

Chiral phosphorus ligands have been widely used in transition metal-catalyzed asymmetric reactions. Herein, we report a new synthesis approach of chiral biaryls containing a phosphorus moiety using P(O)R2-directed Pd-catalyzed C-H activation; the functionalized products are produced with good enantioselectivity.

Access to Bromo-γ-butenolides via Zwitterion-Catalyzed Rearrangement of Cyclopropene Carboxylic Acids.

γ-Butenolides are useful structural motifs in many pharmaceutically relevant compounds. In particular, halogenated γ-butenolides are attractive building blocks because the halogen handles can readily be manipulated to give various functional molecules. In this study, a catalytic synthesis of halogenated γ-butenolides from cyclopropene carboxylic acids was developed using zwitterionic catalysts and N-haloamides as the halogen sources. The catalytic protocol could also be applied to the synthesis of halogenated pyrrolones by using cyclopropene amides as the starting materials.

Zwitterion-Catalyzed Intermolecular Bromoesterifications.

Intermolecular haloesterification is an important class of transformations. The resulting products are valuable building blocks. However, it is often necessary to use super-stoichiometric amount of acid in order to compensate the low reactivity. Herein, we report a zwitterion-catalyzed intermolecular bromoesterification using acid and olefin in an equimolar ratio. Mechanistic study revealed that the charge pair in the zwitterion works synergistically in activating both NBS and carboxylic acid.

Dearomatization of Indoles via Palladium-Catalyzed Allylic C-H Activation.

The first Pd-catalyzed allylic dearomatization of substituted indoles triggered by C-H bond activation is reported. The presence of a catalytic amount of 2,5-DMBQ is proven to be a key factor for the high yield. This one-pot tandem allylic C-H activation/dearomatization sequence provides a straightforward access to 3,3-disubstituted indolines.

Palladium-catalyzed P(O)R2 directed C-H arylation to synthesize electron-rich polyaromatic monophosphorus ligands.

Palladium-catalyzed arylation of (diisopropylphosphoryl)biphenyl skeleton derivatives by the P(O)R2 directed C-H functionalization was reported. The related products were obtained in high regioselectivity and good functional group tolerance was observed. This reaction provided a new and efficient pathway for the synthesis of polyaromatic monophosphorus ligands.

Palladium-catalyzed R2(O)P directed C(sp2)-H acetoxylation.

A novel and efficient Pd-catalyzed C-H acetoxylation is described. The approach uses R2(O)P as a directing group to synthesize various substituted 2'-phosphorylbiphenyl-2-OAc compounds. Notably, the reaction exhibits smooth operation under mild conditions and shows good functional group tolerance. Products are obtained with high selectivity and yields.

Palladium-catalyzed sp2 and sp3 C-H bond activation and addition to isatin toward 3-hydroxy-2-oxindoles.

The first Pd(II)-catalyzed C-H addition to isatins by direct sp(2)/sp(3) C-H bond activation for the construction of 3-substituted-3-hydroxy-2-oxindoles is reported. The bidentate nitrogen ligands were found to promote this reaction. Specifically, the preliminary bioassay indicated that 3-(5-chlorobenzoxazole)-3-hydroxy-N-benzyl-2-oxindole (2w) is a new inhibitor of human kidney cancer and hepatocellular carcinoma cells. Moreover, this reaction system exhibits great functional group tolerance and requires no directing group, extra base, or additives.

Pd(II)-catalyzed Ph2(O)P-directed C-H olefination toward phosphine-alkene ligands.

The Pd(II)-catalyzed Ph2(O)P-directed C-H olefination to synthesize alkene-phosphine compounds is reported. In contrast to previous examples of various directing groups that guide selective C-H activation, the Ph2(O)P group not only acts as the directing group but also serves to construct the alkene-phosphine ligands. The monoprotected amino acid (MPAA) ligand Ac-Leu-OH is found to promote this reaction in a significant manner.