Alkyl Source Research Articles

ChemInform Abstract: Copper‐Catalyzed Alkylarylation of Activated Alkenes Using Isocyanides as the Alkyl Source: An Efficient Radical Access to 3,3‐Dialkylated Oxindoles.

A novel and efficient protocol for the synthesis of 3,3-dialkylated oxindoles is described. The method involves a copper-catalyzed tandem radical addition/cyclization of N-arylacrylamides with the alkyl radicals generated from isocyanides. Two C–C bonds are formed in a single step.

Improving source efficiency for aluminum nitride grown by metal organic chemical vapor deposition

Parasitic pre-reactions are known to play a role in the growth of aluminum nitride (AlN) via metal organic chemical vapor deposition, where they can deplete precursor molecules before reaching the substrate, leading to poor growth efficiency. Studies have shown that reducing the growth pressure and growth temperature results in improved growth efficiency of AlN; however, superior crystal quality and reduced impurity incorporation are generally best obtained when growing at high temperatures. This study shows that, with proper alkyl source dilution, parasitic pre-reactions can be suppressed while maintaining high growth temperatures. The results show an 18× increase in growth rate and efficiency of AlN films: from 0.04 μm h−1 to 0.73 μm h−1, and 26 μm mol−1 to 502 μm mol−1, respectively; under constant TMAl flow and a small change in total gas flow. This results in 6.8% of Al atoms from the injected TMAl being utilized for AlN layer growth for this reactor configuration. This is better than the standard GaN growth, where 6.0% of the Ga atoms injected from TMGa are utilized for GaN growth.

Transition-Metal-Free Regioselective Alkylation of Pyridine N-Oxides Using 1,1-Diborylalkanes as Alkylating Reagents.

Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C-H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thus it can serve as a powerful method for late-stage functionalization.

Transition‐Metal‐Free Regioselective Alkylation of Pyridine N‐Oxides Using 1,1‐Diborylalkanes as Alkylating Reagents

AbstractReported herein is an unprecedented base‐promoted deborylative alkylation of pyridine N‐oxides using 1,1‐diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N‐oxides and 1,1‐diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C−H arylation and methylation of pyridine N‐oxides. The reaction also can be applied for the direct introduction of a methyl group to 9‐O‐methylquinine N‐oxide, thus it can serve as a powerful method for late‐stage functionalization.

Response surface optimization of biodiesel production using immobilized Rhizopus oryzae cells

ABSTRACTBiodiesel (fatty acid methyl or ethyl esters), a clean alternative fuel, has attracted considerable attention as it is a renewable, biodegradable and non-toxic fuel and can generally be used as a substitute for diesel. The present study, biodiesel production from jatropha oil and karanja oil was studied with immobilized Rhizopus oryzae MTCC (262) cells. Prior to the optimization experiments, single point optimization studies were conducted to select the alkyl source (methanol), organic solvent (n-hexane), optimum solvent quantity (20% w/w of oil) and bead size (0.24 cm) using R. oryzae cells. Effect of reaction time (42 h) and optimum agitation speed (150 rpm) on percentage biodiesel yield were studied. Response surface optimization experiments were carried out for optimizing the operating conditions namely reaction temperature, reaction time, added water content, catalyst concentration and molar ratio of alcohol to oil. Maximum biodiesel yields of 80.5% and 78.3% for jatropha oil and karanja oil.

Copper-catalyzed alkylarylation of activated alkenes using isocyanides as the alkyl source: an efficient radical access to 3,3-dialkylated oxindoles.

A novel and efficient protocol for the synthesis of 3,3-dialkylated oxindoles is described. The method involves a copper-catalyzed tandem radical addition/cyclization of N-arylacrylamides with the alkyl radicals generated from isocyanides. Two C-C bonds are formed in a single step.

Silicates as Latent Alkyl Radical Precursors: Visible‐Light Photocatalytic Oxidation of Hypervalent Bis‐Catecholato Silicon Compounds

AbstractThis works introduces hypervalent bis‐catecholato silicon compounds as versatile sources of alkyl radicals upon visible‐light photocatalysis. Using Ir[(dF(CF3)ppy)2(bpy)](PF6) (dF(CF3)ppy=2‐(2,4‐difluorophenyl)‐5‐trifluoromethylpyridine, bpy=bipyridine) as catalytic photooxidant, a series of alkyl radicals, including highly reactive primary ones can be generated and engaged in various intermolecular homolytic reactions. Based on cyclic voltammetry, Stern–Volmer studies, and supported by calculations, a mechanism involving a single‐electron transfer from the silicate to the photoactivated iridium complex has been proposed. This oxidative photocatalyzed process can be efficiently merged with nickel‐catalyzed CC cross‐coupling reactions.

Silicates as Latent Alkyl Radical Precursors: Visible-Light Photocatalytic Oxidation of Hypervalent Bis-Catecholato Silicon Compounds.

This works introduces hypervalent bis-catecholato silicon compounds as versatile sources of alkyl radicals upon visible-light photocatalysis. Using Ir[(dF(CF3)ppy)2(bpy)](PF6) (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, bpy = bipyridine) as catalytic photooxidant, a series of alkyl radicals, including highly reactive primary ones can be generated and engaged in various intermolecular homolytic reactions. Based on cyclic voltammetry, Stern-Volmer studies, and supported by calculations, a mechanism involving a single-electron transfer from the silicate to the photoactivated iridium complex has been proposed. This oxidative photocatalyzed process can be efficiently merged with nickel-catalyzed Csp2-Csp3 cross-coupling reactions.

Palladium-catalyzed regioselective decarboxylative alkylation of arenes and heteroarenes with aliphatic carboxylic acids.

An unprecedented Pd(OAc)2-catalyzed decarboxylative alkylation of unactivated arenes, with aliphatic carboxylic acids as inexpensive alkyl sources, is reported. The alkylation, controlled by the directing group, is regioselective, shows high functional group tolerance, and provides mild access to alkylated indolines, 2-phenylpyridines, and azobenzenes under solvent-free conditions in moderate to high yields.

Oxidative umpolung α-alkylation of ketones.

We disclose a hypervalent iodine mediated α-alkylative umpolung reaction of carbonyl compounds with dialkylzinc as the alkyl source. The reaction is applicable to all common classes of ketones including 1,3-dicarbonyl compounds and regular ketones via their lithium enolates. The α-alkylated carbonyl products are formed in up to 93% yield. An ionic mechanism is inferred based on meticulous analysis, NMR studies, trapping and crossover experiments, and computational studies.

ChemInform Abstract: N‐Alkylation of Tosylamides Using Esters as Primary and Tertiary Alkyl Sources: Mediated by Hydrosilanes Activated by a Ruthenium Catalyst.

AbstractThe selective introductions of both primary and tertiary alkyl groups to tosylamides are achieved by simply changing the hydrosilane and the alkyl ester group.

Palladium‐Catalyzed CH Oxidation of Isoquinoline N‐Oxides: Selective Alkylation with Dialkyl Sulfoxides and Halogenation with Dihalo sulfoxides

AbstractA novel palladium‐catalyzed CH oxidation of isoquinoline N‐oxides has been developed for regioselectively synthesizing substituted isoquinolines. The method represents the first example of using dialkyl sulfoxides as the alkyl sources for the construction of 1‐alkylated isoquinolines. Moreover, the regioselective halogenation of isoquinoline N‐oxides is also successful using dihalo sulfoxides as the halide sources.

Reductive N-Alkylation of Nitroarenes: A Green Approach for the N-Alkylation of Natural Products

A simple, mild, cost-effective, and green approach for the reductive mono-N-alkylation of nitroarenes has been developed. HOAc/Zn are utilized as the reducing system together with a carbonyl compound as an alkyl source in methanol. Excellent yields were obtained with stoichiometric control of mono- over dialkylated products. Application to five complex natural products demonstrated the practical utility of the method.

Comparison studies of InGaN epitaxy with trimethylgallium and triethylgallium for photosensors application

InGaN materials grown by metalorganic chemical vapor deposition (MOCVD) using trimethylgallium (TMG) and triethylgallium (TEG) as alkyl source were compared. Ga-doped ZnO (GZO) films using radio frequency (RF) magnetron sputtering to feature Schottky contacts onto InGaN epitaxial layer with AlN or Mg-doped GaN in-situ capping layer were demonstrated. It is of great potential in application to high performance InGaN photosensors.

N Alkylation of Tosylamides Using Esters as Primary and Tertiary Alkyl Sources: Mediated by Hydrosilanes Activated by a Ruthenium Catalyst

Zweierlei Gruppen zur Auwahl: Durch die rutheniumkatalysierte Umsetzung mit geeigneten Estern und Hydrosilanen können am Stickstoffatom von Tosylamiden entweder primäre oder tertiäre Alkylgruppen selektiv eingeführt werden (siehe Schema; Ts=4-Toluolsulfonyl), wobei die Ester als Alkylquelle wirken. Diese N-Alkylierungen sind nützlich für den Aufbau azacyclischer Naturstoffgerüste.

N Alkylation of Tosylamides Using Esters as Primary and Tertiary Alkyl Sources: Mediated by Hydrosilanes Activated by a Ruthenium Catalyst

The selective introductions of both primary and tertiary alkyl groups to tosylamides are achieved by simply changing the hydrosilane and the alkyl ester group.

Selective photochemical monoalkylation of active methylene compounds by alkenes. A green pathway for carbon–carbon bond formation

A novel photochemical method for selective α-monoalkylation of active methylene compounds has been developed. Aryl substituted alkenes and an aliphatic diene can be used as alkyl sources for these reactions, which proceed via polycyanoarene sensitized, photoinduced electron transfer pathways that are promoted using very mild conditions (ambient temperature, without noble metals and halogens, and with weak bases such as alkali metal carbonate). The reactions that comprise the new synthetic methods developed in this effort are both safe and environmentally friendly. Especially noteworthy is the fact that photochemical alkylation reactions of β-ketoesters (e.g., acetoacetic and malonic esters) can be used in the place of conventional strong base promoted processes.

Pd/C‐catalyzed Reductive Mono‐N‐alkylation of Nitrophenol Derivatives in One‐pot Way

AbstractA range of different nitrophenol derivatives were converted in one‐pot to the corresponding secondary alkyl aminophenols in good to excellent yields by using ketones as alkyl source and hydrogen over 10 wt% Pd/C as reducing agent. In all examples, except for one, the secondary amine was the sole alkylation product isolated. When aldehydes were used as alkyl source, the corresponding tertiary amine as a sole alkylation product was isolated.

Methylation of 2'-deoxyguanosine by a free radical mechanism.

The mechanistic aspects of the methylation of guanine in DNA initiated by methyl radicals that are derived from the metabolic oxidation of some chemical carcinogens remain poorly understood. In this work, we investigated the kinetics and the formation of methylated guanine products by two methods: (i) the combination of *CH3 radicals and guanine neutral radicals, G(-H)*, and (ii) the direct addition of *CH3 radicals to guanine bases. The simultaneous generation of *CH3 and dG(-H)* radicals was triggered by the competitive one-electron oxidation of dimethyl sulfoxide (DMSO) and 2'-deoxyguanosine (dG) by photochemically generated sulfate radicals in deoxygenated aqueous buffer solutions (pH 7.5). The photolysis of methylcob(III)alamin to form *CH3 radicals was used to investigate the direct addition of these radicals to guanine bases. The major end products of the radical combination reactions are the 8-methyl-dG and N2-methyl-dG products formed in a ratio of 1:0.7. In contrast, the methylation of dG by *CH3 radicals generates mostly the 8-methyl-dG adduct and only minor quantities of N2-methyl-dG (1:0.13 ratio). The methylation of the self-complementary 5'-d(AACGCGAATTCGCGTT) duplexes was achieved by the selective oxidation of the guanines with carbonate radical anions in the presence of DMSO as the precursor of *CH3 radicals. The methyl-G lesions formed were excised by the enzymatic digestion and identified by LC-MS/MS methods using uniformly 15N-labeled 8-methyl-dG and N2-methyl-dG adducts as internal standards. The ratios of 8-methyl-G/N2-methyl-G lesions derived from the combination of methyl radicals with G(-H)* radicals positioned in double-stranded DNA or that with the free nucleoside dG(-H)* radicals were found to be similar. Utilizing the photochemical method and dipropyl or dibutyl sulfoxides as sources of alkyl radicals, the corresponding 8-alkyl-dG and N2-alkyl-dG adducts were also generated in ratios similar to those obtained with DMSO.

One-pot method to synthesize 4,6-bis(isopropylamino)resorcinol through hydrodechlorination and catalytically reductive mono-N-alkylation

2-Chloro-4,6-dinitroresorcinol was converted catalytically in one-pot operation to the corresponding N-alkyl secondary aminophenol, 4,6-bis(isopropylamino)resorcinol, in high yield by using acetone as alkyl source and hydrogen as reducing reagent over 10 wt.% Pd/C catalyst. The effects of reaction conditions, such as the amount of acetic acid, concentration of acetone, catalyst amount, and reaction time on the selectivity of 4,6-bis(isopropylamino)resorcinol were investigated.