The Preparation of Acylselenourea and Selenocarbamate Using Isoselenocyanate

Acyl isoselenocyanates were prepared by a reaction of acyl chloride with KSeCN. The acyl isoselenocyanates formed in situ were ready for further reaction without concentration. N-Acyl selenoureas were obtained by a reaction of acyl isoselenocyanates with amines. The reaction of acyl isoselenocyanates with nucleophiles gave the corresponding selenocarbamate. All the compounds were well characterized by using spectral data, such as ¹³C and ⁷⁷Se NMR and X-ray diffraction.     

Stable,Reactive, and Orthogonal Tetrazines: Dispersion Forces Promote the Cycloaddition with Isonitriles

The isocyano group is a structurally compact bioorthogonal functional group that reacts with tetrazines under physiological conditions. Now it is shown that bulky tetrazine substituents accelerate this cycloaddition. Computational studies suggest that dispersion forces between the isocyano group and the tetrazine substituents in the transition state contribute to the atypical structure–activity relationship. Stable asymmetric tetrazines that react with isonitriles at rate constants as high as 57 L mol^?1 s^?1 were accessible by combining bulky and electron‐withdrawing substituents. Sterically encumbered tetrazines react selectively with isonitriles in the presence of strained alkenes/alkynes, which allows for the orthogonal labeling of three proteins. The established principles will open new opportunities for developing tetrazine reactants with improved characteristics for diverse labeling and release applications with isonitriles.     

Stable,Reactive, and Orthogonal Tetrazines: Dispersion Forces Promote the Cycloaddition with Isonitriles

The isocyano group is a structurally compact bioorthogonal functional group that reacts with tetrazines under physiological conditions. Now it is shown that bulky tetrazine substituents accelerate this cycloaddition. Computational studies suggest that dispersion forces between the isocyano group and the tetrazine substituents in the transition state contribute to the atypical structure–activity relationship. Stable asymmetric tetrazines that react with isonitriles at rate constants as high as 57 L mol^?1 s^?1 were accessible by combining bulky and electron‐withdrawing substituents. Sterically encumbered tetrazines react selectively with isonitriles in the presence of strained alkenes/alkynes, which allows for the orthogonal labeling of three proteins. The established principles will open new opportunities for developing tetrazine reactants with improved characteristics for diverse labeling and release applications with isonitriles.     

Reactions of fused dihydro-1,2,4-thiadiazoles with isoselenocyanates giving 6aλ4-thia-1,3,4,6-tetraazapentalene derivatives and 5,10-dihydro-1,2,4-thiaselenazolo[4,5-b][2,4]benzodiazepines

3-Methyl-6,7-dihydro-5H-1,2,4-thiadiazolo[4,5-a]pyrimidine (1) reacted with isoselenocyanates with elimination of acetonitrile and concomitant addition of two molecules of the isoselenocyanate to give 2,3-di-substituted-6,7-dihydro-5H-2aλ⁴-thia-2,3,4a,7a-tetraazacyclopent[cd]indene-1(2H),4(3H)-diselones (6a)–(6j). 3-Methyl-5,10-dihydrobenzo[e]-1,2,4-thiadiazolo[4,5-a][1,3]diazepine (3) likewise reacted with alkyl isoselenocyanates to give the 2,3-dialkyl-5-10-dihydro-2aλ⁴-thia-2,3,4a,10a-tetraazapentaleno[3,3a,4-gh]benzocycloheptene-1,4-diselones (9a)–(9h), but reaction of (3) with aryl isoselenocyanates took place with elimination of acetonitrile and incorporation of one molecule of the aryl isoselenocyanate in the product to give 3-arylimino-5,10-dihydro-1,2,4-thiaselenazolo[4,5-b][2,4]benzodiazepines (10a)–(10h). Structure (10) is a new heterocyclic system. The pyrimidine (1) and the diazepine (3) reacted with aryl isoselenocyanates at room temperature in solvents of low polarity to give zwitterion 1:1 addition compounds (7) and (12), respectively. NMR studies reveal that the thiaselenazoles (10) react in solution with aryl isoselenocyanates to give diaryl diselones (11) in a reversible process involving a Dimroth rearrangement. © 1996 John Wiley & Sons, Inc.     

First synthesis of 1,3-oxaselenepanes

The first synthesis of 1,3-oxaselenepane derivatives by the reaction of aryl isoselenocyanates with 4-bromobutanol in the presence of sodium hydride in THF as a one-pot reaction is described. The Z/E isomerism for the exocyclic carbon-nitrogen double bond in the selenium heterocycles was observed for the first time.     

An approach to a new class of selenosugars : A convenient synthesis of glycosyl isoselenocyanates

A new class of selenosugars—glycosyl isoselenocyanates—has been prepared via reaction of the corresponding glycosyl isocyanides with elemental Se under the catalytic influence of triethylamine. 2,3,4,5,6-Penta-O-acetyl-D-gluconyl isoselenocyanate was also prepared in moderate yield by reaction of 2,3,4,5,6-penta-O-acetyl-D-gluconyl chloride with potassium selenocyanate in anhydrous acetone. The isoselenocyanate structure is ascertained by physical (¹³C-NMR, IR) and chemical methods—formation of selenoureas, and radical induced fragmentation by reaction with tri-n-butyltin hydride via intermediate isocyanide, to 1,5-anhydro-D-hexitols.     

Synthesis of sugar-derived isoselenocyanates, selenoureas, and selenazoles

Aryl, alkyl, and sugar-derived isoselenocyanates were prepared by a one-pot procedure starting from the corresponding formamides, using triphosgene as a dehydrating agent, triethylamine, and black selenium powder. The preparation of sugar selenoureas by coupling of O-protected sugar-derived isoselenocyanates with different amines, and by coupling of unprotected glycopyranosyl amines with phenyl isoselenocyanate was also accomplished. The synthesis of a glucopyranos-2-yl-selenazole starting from O-protected 2-amino-2-deoxy-d-glucose by coupling with benzoyl isoselenocyanate, Se-alkylation with phenacyl bromide, and acid-catalyzed dehydration is also reported. Unprotected N-(β-d-glucopyranosyl)-N′-phenylselenourea was transformed into a 1,2-trans-fused bicyclic isourea upon treatment with aqueous hydrogen peroxide; the same isourea was prepared by a one-pot three-step procedure from β-d-glycopyranosylamine by thiophosgenation, coupling with aniline, and HgO-mediated desulfurization.     

Palladium catalysed synthesis of cyclic amidines and imidates

The palladium catalysed insertion of isonitriles into aryl bromides carrying pendant amine or alcohol groups on the ortho position affords cyclic amidines or imidates in good yield.     

Isoselenocyanates: a powerful tool for the synthesis of selenium-containing heterocycles

Selenium-containing heterocyclic compounds have been well recognized, not only because of their remarkable reactivities and chemical properties, but also because of their diverse pharmaceutical applications. In this context, isoselenocyanates have been emerged as a powerful tool for the synthesis of selenium-containing heterocycles, since they are easy to prepare and store and are safe to handle. In this review the recent advances in the development of synthesis methods for selenium-containing heterocycles from isoselenocyanates are presented and discussed.     

First synthesis of a selenazepane

The first synthesis of perhydroselenazepane derivatives by the reaction of aryl isoselenocyanates with 5-chlorobutylamine in the presence of triethylamine in DMF as a one-pot procedure is described.     

Reactions of 3-Benzylidene-3H-1,2-dithioles and 3-Alkyl-1λ4,2-dithiol-1-ylium Salts with Isonitriles: A Synthesis of 1,6aλ4-Dithia-6-azapentalenes

1,6aλ⁴-Dithia-6-azapentalenes ( 7a )–( 7h ), ( 12a ), and ( 12b ) have been synthesized by the reaction of 5-aryl-3-benzylidene-3H-1,2-dithioles with isonitriles in the presence of phosphoryl chloride and by the reaction of 3-benzyl- and 3-methyl-1λ⁴, 2-dithiol-1-ylium salts with isonitriles. Possible mechanisms for these reactions are discussed. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8 : 479–485, 1997     

Selenium-containing heterocycles from isoselenocyanates: synthesis of 2-methylidene-1,3-selenazolidine derivatives

A convenient and unequivocal synthesis of the title compounds from isoselenocyanates, malononitrile or 2-cyanoacetate, and 1,2-dibromoethane or α-halogenated carboxylic acid derivatives is reported. The proposed reaction mechanism involves in situ cyclization of different halogenated compounds with an intermediate keten-N,Se-acetal, generated by the base promoted nucleophilic addition of the acidic cyanomethylenes to aliphatic and aromatic isoselenocyanates. Chemical and spectroscopic evidence for the structures of the new compounds is presented.     

Synthesis of 5-amino-2-selenoxo-1,3-imidazole-4-carboselenoamides by the reaction of isoselenocyanates with aminoacetonitriles

Reaction of isoselenocyanates with aminoacetonitriles afforded 4-amino-2-selenoxo-1,3-imidazole-2-selenones, whereas reaction with aminopropionitriles led to selenoureas. We confirmed that it is easy to distinguish between selenoamides and selenoureas by comparison of their chemical shift differences in the ⁷⁷Se NMR spectra.     

Reaction of N-fluoropyridinium fluoride with isonitriles and diazo compounds: a one-pot synthesis of (pyridin-2-yl)-1H-1,2,3-triazoles

Reaction of N-fluoropyridinium fluoride generated in situ with a series of isonitriles and diazo compounds led to the formation of the corresponding (pyridine-2-yl)-1H-1,2,3-triazoles in good yields (37-59%). Best outcome was consistently achieved with both aromatic isonitriles and stabilized diazo derivatives. The proposed reaction mechanism involves the intermediate formation of a highly reactive carbene species.     

Oligomerisierung von Nitrilen und Isonitrilen mittels Metallanen und geminalen Dilithiumverbindungen

Oligomerizations of Nitriles and Isonitriles with Metallanes and Geminal Dilithium Compounds The reactions of nitriles and isonitriles with metallanes of group 13 and geminal dilithium compounds, preferably ^tBuELi₂ (E = P, As), will be introduced. The results from investigations concerning intermediates and products exhibit partly significant differences to known reaction systems from transition metal chemistry.     

Synthesis and thermal stability of imino-1,3-dithietanes. Influence of structural factors

The reaction of 1,2-dithiol-3-thiones with isonitriles at room temperature affords imino-1,3-dithietanes. The reaction is reversible. According to ¹H NMR spectroscopy, the rise of the temperature shifts the equilibrium to the starting compounds. The structure of one of the imino-1,3-dithietanes was established by X-ray diffraction.     

Synthesis and Spectroscopic Characterization of Arylated Selenoureas

Abstract

Selenoureas were prepared from isoselenocyanates and structurally characterized by spectroscopic methods and by X-ray crystal structure analyses.     

Vierring-synthesen durch [3 + 1]-cycloaddition . Synthese von 3-imino-azetidinen aus azomethin-yliden und isonitrilen

Azomethine ylide 3 , generated by thermolysis of 3,4-diphenyl-Δ¹-1,2,3-triazoline-5,5-dimethyldicarboxylate 1 , can be trapped by isonitriles to give 3-imino-1,4-diphenylazetidine-2,2-dimethyldicarboxylates 5 . The IR, ¹H-NMR, ¹³C-NMR and mass spectral data of the new compounds are discussed.     

Selenocyanation using a combined reagent of triphenylphosphine and selenocyanogen. A new and simple synthesis of alkyl selenocyanates and symmetrical alkyl diselenides from alcohols

A novel reagent Ph₃SeCN)₂, easily prepared by adding an equimolar amount of tri-phenylphosphine to selenocyanogen solution in methylene chloride and tetrahydrofuran reacts below ?60° with primary alcohols to produce directly the corresponding alkyl selenocyanates and alkyl diselenides in good yields. With secondary alcohols mixtures of selenocyanates and isoselenocyanates are obtained, while tertiary alcohols fail to react with the reagent.     

Benz[c,d]indoles - II. synthesis by the saegusa cyclization

A convenient synthesis of substituted benz[c,d]indoles is described. The method consists in cyclization of bicyclic isonitriles with strong bases such as LDA to the corresponding tricyclic compound.