Endo-Selective Pd-Catalyzed Silyl Methyl Heck Reaction

A palladium (Pd)-catalyzed endo-selective Heck reaction of iodomethylsilyl ethers of phenols and aliphatic alkenols has been developed. Mechanistic studies reveal that this silyl methyl Heck reaction operates via a hybrid Pd-radical process and that the silicon atom is crucial for the observed endo selectivity. The obtained allylic silyloxycycles were further oxidized into (<i>Z</i>)-alkenyldiols

Nanocellulose as Convenient Reaction Media for the FeCl₃ Mediated Mechanochemical Synthesis of 3‑Acylchromones

A solvent free strategy for the mechanochemical synthesis of 3-acylchromones has been developed via FeCl3-nanocellulose mediated dehydrative coupling of ortho-hydroxyarylenaminones and carboxylic acids. The ortho-hydroxyarylenaminones undergo electrophilic domino cyclization followed by an unusual acylation event with carboxylic acids in the presence of FeCl3 as the catalyst and nanocellulose as the reaction media. The protocol was found to be simple, efficient, and environmentally benign to obtain a diverse array of 3-acylchromones with high yields. The protocol features advantages such as the use of cheap and readily available carboxylic acids as acyl source and no requirement of directing groups, oxidants, and solvents. Furthermore, the utilization of a wood-derived material, nanocellulose as the biodegradable reaction media and nontoxic iron salt as the catalyst under very mild and solvent-free conditions makes this acylation protocol very interesting in the perspective of the Green Chemistry principles

Regioselective and Guided C–H Activation of 4‑Nitropyrazoles

A divergent and regioselective approach to 5-aryl-4-nitro-1<i>H</i>-pyrazoles was developed by guided transition-metal-catalyzed arylation of 4-nitro-1<i>H</i>-pyrazoles. This method provides a convenient tool for the functionalization of the pharmacologically relevant pyrazole scaffold. The scope and limitations of the methodology were studied

One-Pot, Three-Component Synthesis of 7-Azaindole Derivatives from N-Substituted 2-Amino-4-cyanopyrroles, Various Aldehydes, and Active Methylene Compounds

An efficient and practical route to 7-azaindole framework has been developed by one-pot, three-component cyclocondensation of N-substituted 2-amino-4-cyanopyrroles, various aldehydes, and active methylene compounds in ethanol or acetic acid at reflux. Reactions involving tetronic acid, indane-1,3-dione, dimedone, and 5-phenylcyclohexane-1,3-dione gave carbocyclic fused 7-azaindoles, whereas Meldrum’s acid, benzoylacetonitrile, and malononitrile resulted in the highly substituted 7-azaindole derivatives, making this strategy very useful in diversity-oriented synthesis (DOS)

Transition-Metal-Catalyzed Arylation of Nitroimidazoles and Further Transformations of Manipulable Nitro Group

Pd- or Ni-catalyzed C–H arylation of 4-nitroimidazole derivatives directed by a manipulable nitro group was developed. The reaction tolerates a wide range of substituted aryl halides and 4-nitroimidazoles. The experiments indicated that the nitro group has influence on regioselectivity of the reaction. In addition, we have shown that the efficiency of the Suzuki–Miyaura cross-coupling reaction of nitroimidazoles is slightly lower in comparison to the direct C–H arylation. The exploration of the chemical potential of the nitro group and a putative reaction mechanism are discussed