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A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 % yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon‐containing by‐products with inexpensive, readily available, and environmentally benign reagents. [ABSTRACT FROM AUTHOR]

A novel strategy to prepare methanol from formic acid without an external reductant is presented. The overall process described herein consists of the disproportionation of silyl formates to methoxysilanes, catalyzed by ruthenium complexes, and the production of methanol by simple hydrolysis. Aqueous solutions of MeOH (>1 mL, >70 % yield) were prepared in this manner. The sustainability of the reaction has been established by recycling of the silicon‐containing by‐products with inexpensive, readily available, and environmentally benign reagents. [ABSTRACT FROM AUTHOR]

A method for the catalytic generation of functionalized aryl alkali metals is reported. These highly reactive intermediates are liberated from silyl‐protected aryl‐substituted diazenes by the action of Lewis basic alkali metal silanolates, resulting in desilylation and loss of N2. Catalytic quantities of these Lewis bases initiate the transfer of the aryl nucleophile from the diazene to carbonyl and carboxyl compounds with superb functional‐group tolerance. The aryl alkali metal can be decorated with electrophilic substituents such as methoxycarbonyl or cyano as well as halogen groups. The synthesis of a previously unknown cyclophane‐like [4]arene macrocycle from a 1,3‐bisdiazene combined with a 1,4‐dialdehyde underlines the potential of the approach. [ABSTRACT FROM AUTHOR]

Es wird über eine Methode zur katalytischen Erzeugung von funktionalisierten Arylalkalimetallverbindungen berichtet. Diese hochreaktiven Intermediate werden aus silylgeschützten, arylsubstituierten Diazenen durch Einwirkung von Lewis‐basischen Alkalimetallsilanolaten freigesetzt, wobei Desilylierung und Verlust von N2 eintreten. Katalytische Mengen jener Lewis‐Basen leiten die Übertragung des Arylnukleophils vom Diazen auf Carbonyl‐ und Carboxyverbindungen mit hervorragender Toleranz gegenüber funktionellen Gruppen ein. Die Arylalkalimetallverbindungen können elektrophile Substituenten wie Methoxycarbonyl‐ oder Cyangruppen sowie Halogene tragen. Die Synthese eines bislang nicht bekannten cyclophanartigen [4]Arenmakrocyclus ausgehend von einem 1,3‐Bisdiazen in Verbindung mit einem 1,4‐Dialdehyd unterstreicht das Leistungsvermögen des Ansatzes. [ABSTRACT FROM AUTHOR]

The silylation of O–H bonds is a useful methodology in organic synthesis and materials science. While this transformation is commonly achieved by reacting alcohols with reactive chlorosilanes or hydrosilanes, we show herein for the first time that silylformates HCO2SiR3 are efficient silylating agents for alcohols, in the presence of a ruthenium molecular catalyst. [ABSTRACT FROM AUTHOR]

An iron catalyst is shown for the first time to promote transfer hydrosilylation with silyl formates and is utilized for the silylation of alcohols. Attractive features of this protocol include the use of an earth-abundant transition-metal catalyst, mild reaction conditions, and the release of gases as the only byproducts (H2 and CO2). [ABSTRACT FROM AUTHOR]

Silyl formates are investigated for the first time as surrogates of hydrosilanes. In the presence of a well-defined ruthenium catalyst, these reagents are shown to promote the chemoselective reduction of a variety of aldehydes by transfer hydrosilylation. Mechanistic investigations have shown that genuine hydrosilane species are avoided during catalysis. The mechanism involves a sequence of decarboxylation/insertion/transmetallation steps. [ABSTRACT FROM AUTHOR]

Silyl formates are investigated for the first time as surrogates of hydrosilanes. In the presence of a well-defined ruthenium catalyst, these reagents are shown to promote the chemoselective reduction of a variety of aldehydes by transfer hydrosilylation. Mechanistic investigations have shown that genuine hydrosilane species are avoided during catalysis. The mechanism involves a sequence of decarboxylation/insertion/transmetallation steps. [ABSTRACT FROM AUTHOR]

N‐Heterocyclic carbenes (NHCs) have drawn considerable interest in the field of nanomaterials chemistry as highly stabilizing ligands enabling the formation of strong and covalent carbon–metal bonds. Applied to gold nanoparticles synthesis, the most common strategy consists of the reduction of a preformed NHC‐AuI complex with a large excess of a reducing agent that makes the particle size difficult to control. In this paper, we report the straightforward synthesis of NHC‐coated gold nanoparticles (NHC‐AuNPs) by treating a commercially available gold(I) precursor with an easy‐to‐synthesize NHC‐BH3 reagent. The latter acts as both the reducing agent and the source of surface ligands operating under mild conditions. Mechanistic studies including NMR spectroscopy and mass spectrometry demonstrate that the reduction of gold(I) generates NHC‐BH2Cl as a by‐product. This strategy gives efficient control over the nucleation and growth of gold particles by varying the NHC‐borane/gold(I) ratio, allowing unparalleled particle size variation over the range of 4.9±0.9 to 10.0±2.7 nm. Our strategy also allows an unprecedented precise and controlled seeded growth of gold nanoparticles. In addition, the as‐prepared NHC‐AuNPs exhibit narrow size distributions without the need for extensive purification or size‐selectivity techniques, and are stable over months. [ABSTRACT FROM AUTHOR]

Benzylsilanes have found increasing applications in organic synthesis as bench‐stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom‐economical silylation of benzylic C(sp3)−H bonds remain scarcely available as specialized directing groups and catalytic systems are needed to outcompete the kinetically‐favored silylation of C(sp2)−H bonds. Herein, we describe the first general and catalytic‐in‐metal undirected silylation of benzylic C(sp3)−H bonds under ambient, transition metal‐free conditions using stable tert‐butyl‐substituted silyldiazenes (tBu−N=N−SiR3) as silicon source. The high activity and selectivity of the catalytic system, exemplified by the preparation of various mono‐ or gem‐bis benzyl(di)silanes, originates from the facile generation of organopotassium reagents, including tert‐butylpotassium. [ABSTRACT FROM AUTHOR]

Benzylsilanes have found increasing applications in organic synthesis as bench‐stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom‐economical silylation of benzylic C(sp3)−H bonds remain scarcely available as specialized directing groups and catalytic systems are needed to outcompete the kinetically‐favored silylation of C(sp2)−H bonds. Herein, we describe the first general and catalytic‐in‐metal undirected silylation of benzylic C(sp3)−H bonds under ambient, transition metal‐free conditions using stable tert‐butyl‐substituted silyldiazenes (tBu−N=N−SiR3) as silicon source. The high activity and selectivity of the catalytic system, exemplified by the preparation of various mono‐ or gem‐bis benzyl(di)silanes, originates from the facile generation of organopotassium reagents, including tert‐butylpotassium. [ABSTRACT FROM AUTHOR]

A transfer hydrosilylation of ketones employing silyl formates as hydrosilane surrogates under mild conditions is presented. A total of 24 examples of ketones have been successfully converted to their corresponding silyl ethers with 61–99% yields in the presence of a PNHP-based ruthenium catalyst and silyl formate reagent. The crucial role of the ligand for the transformation is demonstrated. [ABSTRACT FROM AUTHOR]

Among all functional groups, alkynes occupy a privileged position in synthetic and medicinal chemistry, chemical biology, and materials science. Thioalkynes, in particular, are highly useful, as they combine the enhanced reactivity of the triple bond with a sulfur atom frequently encountered in bioactive compounds and materials. Nevertheless, general methods to access these compounds are lacking. In this article, we describe the mechanism and full scope of the alkynylation of thiols using ethynyl benziodoxolone (EBX) hypervalent iodine reagents. Computations led to the discovery of a new, three-atom concerted transition state with a very low energy barrier, which rationalizes the high reaction rate. On the basis of this result, the scope of the reaction was extended to the synthesis of aryl- and alkyl-substituted alkynes containing a broad range of functional groups. New sulfur nucleophiles such as thioglycosides, thioacids, and sodium hydrogen sulfide were also alkynylated successfully to lead to the most general and practical method yet reported for the synthesis of thioalkynes. [ABSTRACT FROM AUTHOR]