The synthesis of fructose-based surfactants.

This study describes the synthesis of a new class of surfactants that is based on the bioderived building blocks fructose, fatty acid methyl esters (FAME), and hydroxy propionitrile (cyanoethanol, 3-HP). The synthesis is scalable, is carried out at ambient conditions, and does not require chromatography. The produced surfactants have excellent surfactant properties with critical micelle concentrations and Krafft points comparable to current glucose-based surfactants.

Pd Nanoparticle-Catalyzed Stereospecific Mizoroki-Heck Arylation of -1,2-Disilylarylethylenes.

In the presence of catalytic amounts of Pd nanoparticles, generated from Pddba/Ag(I), -1,2-ditrimethylsilylarylethylenes undergo with aryl iodides a stereospecific Mizoroki-Heck arylation leading to -ditrimethylsilyldiarylethylenes. This chemoselectivity is in contrast to that of their trimethylgermyl analogues, which are arylated at the position of the C-Ge bonds. -1,2-Ditrimethylsilylarylethylenes are completely unreactive under the standard reaction conditions.

Site-Selective Electrochemical Oxidation of Glycosides.

Quinuclidine-mediated electrochemical oxidation of glycopyranosides provides C3-ketosaccharides with high selectivity and good yields. The method is a versatile alternative to Pd-catalyzed or photochemical oxidation and is complementary to the 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-mediated C6-selective oxidation. Contrary to the electrochemical oxidation of methylene and methine groups, the reaction proceeds without oxygen.

Substitution-Dependent Ring-Opening Hydrosilylation or Dehydrogenative Hydrosilylation of Cyclopropyl Aldehydes and Ketones Catalyzed by Au Nanoparticles.

The reaction between hydrosilanes and aryl-substituted cyclopropyl aldehydes or ketones catalyzed by Au nanoparticles supported on TiO provides two distinct ring-opening reaction motifs depending on the substituents. 2-Aryl-substituted cyclopropyl carbonyl compounds form linear enol ethers via formal silyl hydride addition on the carbon atom bearing the aryl group. Under the reaction conditions, the hydrosilylation adducts undergo hydrolytic silyl deprotection to form acyclic aldehydes or ketones.

Reduction of the Diazo Functionality of α-Diazocarbonyl Compounds into a Methylene Group by NHBH or NaBH Catalyzed by Au Nanoparticles.

Supported Au nanoparticles on TiO (1 mol%) are capable of catalyzing the reduction of the carbene-like diazo functionality of α-diazocarbonyl compounds into a methylene group [C=(N) → CH] by NHBH or NaBH in methanol as solvent. The Au-catalyzed reduction that occurs within a few minutes at room temperature formally requires one hydride equivalent (B-H) and one proton that originates from the protic solvent. This pathway is in contrast to the Pt/CeO-catalyzed reaction of α-diazocarbonyl compounds with NHBH in methanol, which leads to the corresponding hydrazones instead.

β-Borylation of conjugated carbonyl compounds with silylborane or bis(pinacolato)diboron catalyzed by Au nanoparticles.

Conjugated aldehydes and ketones undergo reaction with Me2PhSiBpin (pin: pinacolato) catalyzed by Au nanoparticles supported on TiO2 forming exclusively the β-borylation products, via the intermediate formation of the labile silaboration adducts. This chemoselectivity pathway is complementary to the so far known analogous reaction catalyzed by other metals, where β-silylation occurs instead. β-Borylation also occurs with pinBBpin under identical reaction conditions in a variety of conjugated carbonyl compounds, including esters and amides which are unreactive in their attempted Au-catalyzed silaboration.

Isomerization of Epoxides into Allylic Alcohols Catalyzed by Supported Au Nanoparticles on TiO: A Mechanistic Insight.

Based on primary and β-secondary isotope effects, it is established that the isomerization of epoxides into allylic alcohols catalyzed by supported Au nanoparticles proceeds via an unsymmetrical concerted transition state in which there is partial positive charge developing on the C-O carbon atom progressing C-H abstraction. A carbocationic intermediate can be formed only in cases of sufficient stabilization of the positive charge by appropriate substituents.

Cycloisomerization of Conjugated Allenones into Furans under Mild Conditions Catalyzed by Ligandless Au Nanoparticles.

Au nanoparticles supported on TiO (1 mol %) catalyze the quantitative cycloisomerization of conjugated allenones into furans under very mild conditions. The reaction rate is accelerated by adding acetic acid (1 equiv), but the acid does not participate in the protodeauration step as in the corresponding Au(III)-catalyzed transformation. The process is purely heterogeneous, allowing thus the recycling and reuse of the catalyst effectively in several runs.

Supported Au Nanoparticles-Catalyzed Regioselective Dehydrogenative Disilylation of Allenes by Dihydrosilane.

Supported Au nanoparticles on TiO catalyze the unprecedented dehydrogenative disilylation of monosubstituted and 1,1-disubstituted allenes by Et SiH exclusively on the terminal double bond in a stereoselective manner. Treatment of the disilylation products with H O, in a one-pot operation also catalyzed by Au/TiO , leads to 3-alkylidene-1,2,5-oxadisilolanes, an unknown class of heterocyclic compounds, which are excellent scaffolds for the stereoselective synthesis of alkenes under Hiyama-type cross-coupling conditions.

Reaction of Aromatic Carbonyl Compounds with Silylborane Catalyzed by Au Nanoparticles: Silylative Pinacol-type Reductive Dimerization via a Radical Pathway.

Aromatic aldehydes and acetophenones undergo silylative pinacol-type reductive dimerization in their reaction with silylborane pinB-SiMePh (pin: pinacolato) catalyzed by supported Au nanoparticles on TiO. It is proposed that after initial activation of silylborane by Au nanoparticles and addition to the carbonyl functionality of an aromatic aldehyde or ketone, an aryl silyloxy radical is generated from the collapse of the intermediate adduct, which then dimerizes through a chain process. The silyloxy radical was almost quantitatively trapped in the presence of TEMPO.

Au Nanoparticle-Catalyzed Insertion of Carbenes from α-Diazocarbonyl Compounds into Hydrosilanes.

Supported Au nanoparticles on TiO catalyze the insertion of carbenes from α-diazocabonyl compounds into hydrosilanes. It is proposed that the transformation involves two modes of catalytic activation: formation of nucleophilic Au carbenes on the surface of nanoparticle via expulsion of N and activation of the Si-H bond of hydrosilane on Au nanoparticle, followed by coupling of the chemisorbed species. No external ligands or additives are required, while the process is purely heterogeneous, thus allowing the recycling and reuse of the catalyst.

Ligandless Regioselective Hydrosilylation of Allenes Catalyzed by Gold Nanoparticles.

The first example of Au-catalyzed hydrosilylation of allenes is presented using recyclable gold nanoparticles as catalyst, without the requirement of any external ligands or additives. The hydrosilane addition takes place on the more substituted double bond of terminal allenes in a highly regioselective manner. The observed regioselectivity/reactivity modes are attributed to steric and electronic factors.

Supported gold nanoparticle-catalyzed cis-selective disilylation of terminal alkynes by σ disilanes.

Supported gold nanoparticles on metal oxides (1 mol %) catalyze for the first time the cis-selective disilylation of terminal alkynes by 1,2-disilanes in isolated yields up to 94%. It is likely that the reaction proceeds through oxidative insertion of the σ Si-Si bond of disilanes on gold followed by 1,2-addition to the alkyne.