Trimethylsilyl Isothiocyanate Research Articles

Synthetic and mechanistic study on the conjugate isothiocyanation of enones with trimethylsilyl isothiocyanate.

Alkyl isothiocyanates (R-NCS) have pharmacological applications and provide a synthetic handle to various functional groups including thioureas. There are however few methods to access alkyl isothiocyanates through the creation of the C-N bond. We have developed a simple approach for the conjugate isothiocyanation of enones by trimethylsilyl isothiocyanate (TMSNCS), which proceeds through the 1,4-addition of the weak isothiocyanate nucleophile to activated enones in the absence of external promoters. This method avoids the direct use of highly toxic acids and bases, produces β-isothiocyanato carbonyl products in yields of 87-98% under mild conditions (less than 6 hours at 0 °C), and displays wide functional group tolerance. Density functional theory calculations highlighted competing cationic and anionic mechanisms, where the enone activation by the TMSNCS reagent is accelerated in protic solvents. The selective formation of the isothiocyanate vs. thiocyanate isomers is explained by the thermodynamically-controlled nature of the reaction in which only the conjugate isothiocyanation is exergonic.

Carboxyl-Terminal Sequencing: COOH-Amino Acid Activation with DCC or TBTU

Abstract: The present study explores conditions to activate the carboxyl group before the coupling of C-terrninal amino acid with Trimethylsilyl -isothiocyanate (TMS-ITC). Protected amino acids and different peptides were used as model and 1,3'-Dicyclohexylcarbodiimide (DCC) plus 1-Hydroxybenzotriazole (HOBt) and 2-(lH-Benzotriazol-l-y)- 1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) plus HOBt were used as carboxyl activators. The coupling reaction of activated AA with TMS-ITC was temperature dependent and the best yield (100 % of coupling) was obtained at 70°C, when DCC or TBTU both with HOBt were used as activating reagents.

Towards a Better Understanding of Redox Shuttle Generation in Lfp/Graphite and NMC811/Graphite Cells By Systematic Investigation of Different Electrolyte Additives

Recent observations by our group show the creation of a reversible shuttle species in LFP/graphite and NMC811/graphite cells with 3:7 ethylene carbonate:dimethyl carbonate (EC:DMC) based electrolytes. This is indicated by a high reversible self-discharge of these cells in the absence of electrolyte additives. Electrolyte extraction from pouch cells after formation allowed to directly investigate the electrolytes for redox shuttle currents. For this purpose, the extracted electrolytes were inserted into coin cells with an Al foil as the working electrode (WE) and a Li foil as the counter electrode (CE). The measured cyclic voltammetry (CV) of the coin cells show a clear relationship between high formation temperature and high shuttle currents. Interestingly, the addition of vinylene carbonate (VC) to the electrolyte completely prevents the shuttle current, even at elevated formation temperatures. [1]In this study, we systematically investigate the effect of various electrolyte additives on the generation of shuttle molecules. LFP/graphite and NMC811/graphite pouch cells were filled with electrolyte consisting of 3:7 EC:DMC with 1.5 M lithium hexafluorophosphate (LiPF6) and different additives. The pouch cells were formed at different temperatures, TF. The electrolytes were then extracted and inserted into the aforementioned coin cell setup for CV measurements.We have found that additives such as VC, fluoroethylene carbonate (FEC), ethylene sulfate (DTD), prop-1-ene-1,3-sultone (PES), and triallyl phosphate (TAP), which are known to create a stable solid electrolyte interphase (SEI), [2-4] prevent shuttle current in the CV. On the other hand, additives such as succinonitrile (SN) and trimethylsilyl isothiocyanate (TMSNCS), which do not contribute to the formation of a better SEI, [5,6] cannot prevent the shuttle current. This suggests that the formation of the shuttles is due to a poor SEI and therefore occurs at the interface between electrolyte and graphite anode.Analogue experiments with DMC as only solvent instead of 3:7 EC:DMC show similar shuttle currents in CVs, which suggests that linear carbonates such as DMC are required to form the shuttle.Figure 1 shows CVs for 1.5 M LiPF6 DMC electrolyte. The shuttle current appears to be the same for electrolyte extracted from LFP/graphite and NMC811/graphite cells ranging up to 6 μA in both cases. This indicates that the shuttle is formed independently of the cathode material, and therefore gives rise to the hypothesis that it is formed at the anode-electrolyte interface. Figure 1 also shows that the shuttle current increases with higher formation temperatures TF.

Copper‐Catalyzed Remote Direct Thiocyanation of Alkyl C(sp3)−H Bonds

AbstractA method for site‐selective intermolecular C(sp3)−H thiocyanation of aliphatic sulfonamides is developed using cheap trimethylsilyl isothiocyanate (TMSNCS) as the thiocyanation reagent, catalyzed by simple Cu(I)/phenanthroline complex. The mild, and modular protocol allows remote C(sp3)−H thiocyanation in promising yields with a broad substrate scope.magnified image

Copper-catalyzed 1,3-aminothiocyanation of arylcyclopropanes.

A copper-catalyzed 1,3-aminothiocyanation of arylcyclopropanes with N-fluorobenzenesulfonimide (NFSI) and trimethylsilyl isothiocyanate (TMSNCS) has been developed for the first time, efficiently synthesizing a series of γ-aminothiocyanate derivatives in moderate to excellent yields from readily available substrates under mild conditions. The practicability of the reaction was demonstrated by gram-scale preparation. Furthermore, the easily prepared γ-aminothiocyanate derivatives were verified to be versatile building blocks.

ChemInform Abstract: Catalyst‐Free Isothiocyanatoalkylthiation of Styrenes with (Alkylthio)pyrrolidine‐2,5‐diones and Trimethylsilyl Isothiocyanate.

A simple and efficient catalyst-free method for isothiocyanatoalkylthiation of styrenes has been developed. The protocol uses (alkylthio)pyrrolidine-2,5-diones and trimethylsilyl isothiocyanate as the isothiocyanatoalkylthiolating reagents, dimethylformamide (DMF) as the solvent, and the reactions were completed within one hour with tolerance of some functional groups. No catalyst and additive were required in the reaction system, which avoided any contamination of transition metal catalysts in the target products. Therefore, the present method provides a convenient, efficient and practical strategy for the synthesis of compounds by a combination of sulfides and isothiocyanates.

Catalyst‐Free Isothiocyanatoalkylthiation of Styrenes with (Alkylthio)pyrrolidine‐2,5‐diones and Trimethylsilyl Isothiocyanate

AbstractA simple and efficient catalyst‐free method for isothiocyanatoalkylthiation of styrenes has been developed. The protocol uses (alkylthio)pyrrolidine‐2,5‐diones and trimethylsilyl isothiocyanate as the isothiocyanatoalkylthiolating reagents, dimethylformamide (DMF) as the solvent, and the reactions were completed within one hour with tolerance of some functional groups. No catalyst and additive were required in the reaction system, which avoided any contamination of transition metal catalysts in the target products. Therefore, the present method provides a convenient, efficient and practical strategy for the synthesis of compounds by a combination of sulfides and isothiocyanates.magnified image

Difunctionalization of Alkenes Using 1-Chloro-1,2-benziodoxol-3-(1H)-one.

Difunctionalization of alkenes with 1-chloro-1,2-benziodoxol-3-(1H)-one (1) was investigated. Various additional nucleophiles were tested, and oxychlorination, dichlorination, azidochlorination, chlorothiocyanation, and iodoesterfication were demonstrated. The oxychlorination product was obtained efficiently when the reaction was operated in water. Dichlorination occurred in the presence of a Lewis basic promoter, such as 4-phenylpyridine N-oxide, as an additive. The reaction with in situ-generated azido anion afforded azidochlorinated compounds with a chlorine atom at the terminal position, while the reaction with trimethylsilyl isothiocyanate produced chlorothiocyanation adducts with a chlorine atom at the benzylic position. On the other hand, when 1 was treated with tetra-n-butylammonium iodide prior to the addition of alkenes, only iodoesterification occurred selectively. These mild reactions enable convenient site-selective difunctionalizations of substrates having two alkene moieties. NMR experiments suggested that the electrophilic reactive species in each reaction varied depending on the nature of the added nucleophile.

Trimethylsilyl Isothiocyanate (TMSNCS)

The versatility of trimethylsilyl isothiocyanate (TMSNCS) as a reagent is impressive, especially in heterocycle synthesis. TMSNCS is also commonly used in reactions of thiocyanation and isothiocyanation. The advantages of TMSNCS are moderated toxicity, chemical stability, high tolerance with other functional groups, and ease of handling. This paper highlights a selection of many different and recently reported types of reactions that this reagent is able to promote.

A Facile One-Step Multi-Component Approach toward the Synthesis of 3-(2-Amino-4-Thiazolyl)Coumarins by using Trimethylsilyl Isothiocyanate and their Antioxidant and Anti-Inflammatory Activity

GRAPHICAL ABSTRACT

Copper-Catalyzed Intermolecular Trifluoromethylthiocyanation of Alkenes: Convenient Access to CF3-Containing Alkyl Thiocyanates.

A highly selective and efficient approach for the direct trifluoromethylthiocyanation of alkenes has been developed using trimethylsilyl isothiocyanate (TMSNCS) as the thiocyanating agent and Togni reagent as the CF3 source in the presence of copper(I) catalyst. Both activated and unactivated alkenes work well to deliver various CF3-containing thiocyanates.

A novel one pot multi-component strategy for facile synthesis of 5-aryl-[1,2,4]triazolidine-3-thiones

We have disclosed an efficient, one pot, novel multi-component approach for the synthesis of 5-aryl-[1,2,4]triazolidine-3-thiones from aldehyde, hydrazine hydrate, and trimethylsilyl isothiocyanate (TMSNCS) in the presence of catalytic amount of sulfamic acid. High yields, easy work-up procedure, no chromatographic separation, and novelty in multi-component strategy are the main merits of the present strategy.

A simple, three-component synthesis of 2-aminothiazoles using trimethylsilyl isothiocyanate

Abstract The first multicomponent, solution-phase protocol to prepare privileged 2-aminothiazoles from α-bromocarbonyl compounds and amines (aromatic and aliphatic) using commercially available trimethylsilyl isothiocyanate is described.

ChemInform Abstract: Trimethylsilyl Isothiocyanate (TMSNCS): An Efficient Reagent for the One‐Pot Synthesis of Mercapto‐1,2,4‐triazoles.

A mild, convenient, and efficient one-pot synthesis of mercapto-1,2,4-triazoles is described. Various hydrazides efficiently reacted with trimethylsilyl isothiocyanate (TMSNCS) under basic condition to give mercapto-1,2,4-triazoles in high yields.

Mild and convenient one-pot synthesis of 2-amino-1,3,4-thiadiazoles using trimethylsilyl isothiocyanate (TMSNCS)

A novel and efficient one-pot method has been developed for the synthesis of 2-amino-1,3,4-thiadiazoles using various carboxylic acid hydrazides with trimethylsilyl isothiocyanate (TMSNCS). In situ preparation of various thiosemicarbazides by the reaction of different carboxylic acid hydrazides with trimethylsilyl isothiocyanate (TMSNCS), followed by cyclodehydration of thiosemicarbazides under acidic conditions gave 2-amino-1,3,4-thiadiazoles in high yields (71–87%).

Mild and convenient one-pot synthesis of 2-amino-1,3,4-oxadiazoles promoted by trimethylsilyl isothiocyanate (TMSNCS)

A mild, convenient, and efficient one-pot synthesis of amino-1,3,4-oxadiazoles is described. In situ preparation of various thiosemicarbazides by the reaction of different carboxylic acid hydrazides with trimethylsilyl isothiocyanate (TMSNCS), followed by cyclodesulfurization of thiosemicarbazides under basic conditions in the presence of I2/KI resulted in 2-amino-1,3,4-oxadiazoles in high yields (79–94%).

Trimethylsilyl isothiocyanate (TMSNCS): an efficient reagent for the one-pot synthesis of mercapto-1,2,4-triazoles

A mild, convenient, and efficient one-pot synthesis of mercapto-1,2,4-triazoles is described. Various hydrazides efficiently reacted with trimethylsilyl isothiocyanate (TMSNCS) under basic condition to give mercapto-1,2,4-triazoles in high yields.

ChemInform Abstract: Reaction of Unsaturated Compounds with Ethyl Benzenesulfenate and Trimethylsilyl Isothiocyanate.

AbstractThe regio‐ and stereoselectivities of reactions of alkenes, dienes, and alkynes with ethyl benzenesulfenate (II) and trimethylsilyl isothiocyanate (III) are studied.

Reaction of unsaturated compounds with ethyl benzenesulfenate and trimethylsilyl isothiocyanate

A new method for the synthesis of thiocyanato- and isothiocyanatoalkyl phenyl sulfides by the reaction of unsaturated compounds with ethyl benzenesulfenate and trimethylsilyl isothiocyanate has been suggested. Regio- and stereoselectivity of the reaction was studied, having taken alkenes, dienes, and alkynes as examples.

ChemInform Abstract: Noncatalyzed Addition of Trimethylsilyl Isothiocyanate to Aziridines and Cyclohexene Oxide.

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