Electrophilicity–Nucleophilicity Scale Also in the Gas Phase

Nucleophilicity and Electrophilicity in the Gas Phase: Silane Hydricity

Hydricity is of great import as hydride transfer reactions are prominent in many processes, including organic synthesis, photoelectrocatalysis, and hydrogen activation. Herein, the kinetic hydricity of a series of silanes is examined in the gas phase. Most of these reactions have not heretofore been studied in vacuo and provide valuable data that can be compared to condensed-phase hydricity, to reveal the effects of solvent. Both experiments and computations are used to gain insight into mechanism and reactivity. In a broader sense, these studies also represent a first step toward systematically understanding nucleophilicity and electrophilicity in the absence of a solvent.

Kinetic hydricity of silane hydrides in the gas phase

Gas-phase experimental and computational methods reveal unknown intrinsic hydricity/nucleophilicity and electrophilicity parameters.

Herein, gas phase studies of the kinetic hydricity of a series of silane hydrides are described. An understanding of hydricity is important as hydride reactions figure largely in many processes, including organic synthesis, photoelectrocatalysis, and hydrogen activation. We find that hydricity trends in the gas phase differ from those in solution, revealing the effect of solvent. Calculations and further experiments, including H/D studies, were used to delve into the reactivity and structure of the reactants. These studies also represent a first step toward systematically understanding nucleophilicity and electrophilicity in the absence of solvent.

Direct dendronization of polystyrenes using dendritic diarylcarbenium ion pools

Dendritic diarylcarbenium ions reacted with unfunctionalized polystyrenes to give dendronized polymers, which were characterized by MALDI-TOF MS and AFM.

Versatile and expeditious synthesis of aurones via Au I-catalyzed cyclization

Aurones are conveniently formed in a three-step procedure including a goldI-catalyzed cyclization of 2-(1-hydroxyprop-2-ynyl)phenols as a highly regio- and stereoselective key step. A wide diversity of derivatives can be obtained starting from substituted salicylaldehydes. Synthesis of natural 4,6,3',4'-tetramethoxyaurone and structure revision of two natural products (dalmaisione D and 4'-chloroaurone) were achieved.

Tandem Bis-aldol Reaction of Ketones: A Facile One-Pot Synthesis of 1,3-Dioxanes in Aqueous Medium

A novel tandem bis-aldol reaction of ketone with paraformaldehyde catalyzed by polystyrenesulfonic acid in aqueous medium delivers 1,3-dioxanes in high yield. This one-pot, operationally simple microwave-assisted synthetic protocol proceeds efficiently in water in the absence of organic solvent, with excellent yield.

Oxidative Generation of Diarylcarbenium Ion Pools

"Cation pools" of diarylcarbenium ions have been generated by the oxidative C-H bond dissociation of diarylmethanes using anodic oxidation. "Diarylcarbenium ion pools" thus generated react with various nucleophiles, such as allylsilanes, ketene silyl acetals, and aromatic compounds. The reductive homocoupling of the "diarylcarbenium ion pool" has been achieved. The dimer thus obtained also serves as a precursor of the "diarylcarbenium ion pool" via oxidative C-C bond dissociation. [reaction: see text]

Benzene loss from trityl cations--a mechanistic study

Triarylmethyl cations eliminate substituted benzene in the gas phase, upon activation. The mechanism of this process has been studied using deuterium labeling, substituent effects, and density functional theory calculations. It is shown that this apparently simple dissociation is in fact a complicated stepwise process that involves several consecutive hydride shifts. The combination of experimental evidence and computational results leads to a clear description of transition states and reaction intermediates.

Pummerer fragmentation vs. Pummerer rearrangement: a mechanistic analysis

Depending upon the nature of the substituent at the beta-position of the sulfoxide moiety, a Pummerer reaction can be oriented "at will" towards Calpha-H (rearrangement) or Calpha-Cbeta (fragmentation) bond cleavage.