Nukleophile Addition von Lithiumorganylen an das N,N-Diethyl-10-(trimethylsilyl)-1, 6-methano[10]annulen-2-carboxamid

Nucleophilic Addition of Lithiumorganyles to N,N-Diethyl-10-(trimethylsilyl)-1,6-methano[10]annulene-2-carboxamide Reaction of lithiumorganyles with N,N-diethyl-10-(trimethylsilyl)-1,6-methano[10]annulene-2-carboxamide followed by quenching with H₂O or MeI yields 2,3-dihydro derivatives of 1,6-methano[10]annulene.     

Reactions of Bis(chloromethyl)phosphinic(-Phosphinothioic) Chlorides with Silylated Carbamates and Trimethylsilyl N-Trimethylsilylacetimidoate

Bis(chloromethyl)phosphinic chloride reacts with trimethylsilyl methylcarbamate in benzene in the presence of a base to give trimethylsilyl bis(chloromethyl)phosphinate. The same reaction performed without a solvent and in the absence of a base yields trimethylsilyl bis(chloromethyl)phosphinate and bis(chloromethyl)phosphinic anhydride. Reaction of bis(chloromethyl)phosphinic chloride with trimethylsilyl diethylcarbamate yields N,N-diethylbis(chloromethyl)phosphinic amide. The reaction of bis(chloromethyl)phosphinic (-phosphinothioic) chlorides with trimethylsilyl N-trimethylsilylacetimidoate was studied.     

Stereoselective Peterson Olefinations from Bench‐Stable Reagents and N‐Phenyl Imines

The synthesis of bench‐stable α,α‐bis(trimethylsilyl)toluenes and tris(trimethylsilyl)methane is described and their use in stereoselective Peterson olefinations has been achieved with a wide substrate scope. Product stereoselectivity was poor with carbonyl electrophiles (E/Z ～1:1 to 4:1) though this was significantly improved by employing the corresponding substituted N‐benzylideneaniline (up to 99:1) as an alternative electrophile. The olefination byproduct was identified as N,N‐bis(trimethylsilyl)aniline and could be easily separated from product by aqueous acid extraction. Evidence for an autocatalytic cycle has been obtained.     

Preparation of trimethylsilyl ethers of 3-azetidinols. Scope and Limitations

Preparation of the trimethylsilyl ethers of 1-alkyl-3-azetidinols from non-hindered primary amines and epichlorohydrin by conversion of the intermediate 1-(alkylamino)-3-chloro-2-propanols to their trimethylsilyl ethers by either N-(trimethylsilyl)acetamide or by 1-(trimethylsilyl)imidazole followed by ring closure in acetonitrile is described. This sequence of reactions fails for aromatic amines, but appears to be general for all primary aliphatic amines, although the condensation of hindered amines with epichlorohydrin occurs slowly. Several novel azetidinols, in which the N-alkyl substituent itself contains a second heterocyclic system, are reported. In addition, the pK_A's of several m. and p-substituted 1-benzylazetidinols correlates well with the Hammett equation.     

Synthesis and some physicochemical properties of the carbazine acid silyl esters

Structure of the dimethylcarbazine acid trimethylsilyl ether and pyrolysis of its derivative, the trimethylsilyl ester of N,N-dimethyl-N′-trimethylsilylcarbazine acid, were studied by the metods of X-ray diffraction and gas chromatography/mass spectrometry. The presence of the bifurcated hydrogen bonds between the trimethylsilyl dimethylcarbazinate molecules was detected. It was revealed why impossible to obtain dimethylaminoisocyanate even by the low-temperature pyrolysis.     

Halogenation of [2-(trimethylsilyl)ethoxy]methyl (SEM) protected 2,2′-Bi-H-imidazole

2,2′-Bi-1H-imidazole, when protected with the [2-(trimethylsilyl)ethoxy]methyl (SEM) blocking group, on treatment with N-bromosuccinimide or N-chlorosuccinimide yields predominantly the monohalogenated derivatives 4a and 4b. The [2-(trimethylsilyl)ethoxy]methyl group is subsequently removed to yield pure mono-halo-2,2′-bi-H-imidazoles 2 .     

An Investigation into Domino‐Heck Reactions of N‐Acylamino‐Substituted Tricyclic Imides: Synthesis of New Prospective Pharmaceuticals

Heck and domino‐Heck reactions of unsaturated N‐acylamino‐substituted tricyclic imides with aryl(heteroaryl) iodides and phenyl‐ or (trimethylsilyl)acetylene were either carried out in the presence of formate or phenyl‐ and (trimethylsilyl)acetylene, respectively. The C? C coupling reactions appeared to be completely diastereoselective, giving the corresponding N‐acylamino‐5‐exo‐aryl (heteroaryl)‐ ( 5a – c, 6a , b ), N‐(benzoylamino)‐5‐exo‐phenyl‐6‐exo‐[(trimethylsilyl)ethynyl]‐ ( 5d ), or 5‐exo‐(4‐chlorophenyl)‐N‐(2,2‐dimethylpropanoylamino)‐6‐exo‐(phenylethynyl)bicyclo[2.2.1]heptane‐2‐endo,3‐endo‐dicarboximide ( 6c ) (Schemes 3 and 4).     

A Novel Concept for Combinatorial Chemistry in Solution: Synthesis of Highly Substituted Pyrrolidines by Multicomponent Domino Reactions

The multicomponent domino Knoevenagel hetero‐Diels? Alder hydrogenation process of N‐[(benzyloxy)carbonyl(Cbz)‐protected amino aldehydes with N,N‐dimethylbarbituric acid and the trimethylsilyl enol ethers 1 – 3 leads to the formation of the substituted pyrrolidines 12 – 15 . Under the same conditions, reaction of the trimethylsilyl enol ether 4 , obtained from acetophenone, gave the primary amines 18a , b probably due to a hydrogenolytic cleavage of the intermediately formed pyrrolidines. The zwitterionic products were obtained in high purity simply by precipitation with Et₂O.     

Catalytic silylotropy inN-trimethylsilylpyrazole derivatives

Silylotropy in 4-substitutedN-trimethylsilypyrazoles is studied by dynamic¹H,¹³C, and²⁹Si NMR spectroscopy. The catalytic 1,2-migration of a trimethylsilyl group in 4-halo-N-trimethylsilylpyrazoles was detected. Silylotropy inN-trimethylsilylpyrazoles in the presence of halogens of trimethylhalosilanes is believed to proceed through formation ofN,N-bis(trimethylsilyl)pyrazolium salts, the barrier of silylotropy in pyrazoles being markedly reduced.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 3011–3013, December, 1996.     

Reactions of hexaorganyldigermoxanes with O-trimethylsilyl carbamates

Hexa-n-butyl- and hexaisopentyldigermoxanes but not hexaphenyldigermoxane react with O-trimethylsilyl N,N-diethylcarbamate and trimethylsilyl piperidinocarboxylate to give O-triorganylgermyl carbamates.     

Alkali Metal and Trimethylsilyl Carbamoselenothioates – Synthesis,Structure, and some Reactions

This paper describes the synthesis and some reactions of potassium, rubidium, cesium and trimethylsilyl carbamoselenothioates. The potassium salts were synthesized in 70–80 % yields by reacting the corresponding thiocarbamoyl chlorides with potassium selenide in acetonitrile. Furthermore, the rubidium and cesium salts were obtained in good yields by treating the trimethylsilyl esters with the corresponding metal fluorides. The crystal structure of acetonitrile‐solvated potassium N,N‐dimethylcarbamoselenothioate consisted of dimeric units, featuring μ‐carbamoselenothioate anions associated with potassium cations that are located on the upper and lower sides of a plane involving two opposing carbamoselenothioate groups. These heavier alkali metal salts readily reacted with alkyl halides to give both S‐ and Se‐alkyl esters. The reaction of the potassium salts with trimethylsilyl chlorides forms S‐ and Se‐trimethylsilyl carbamoselenothioates which are in equilibrium. The reaction of the salts and silyl esters with organo Group‐14 and ‐15 elements halides gave exclusively the corresponding Se‐substituted products in good yields.     

Studies on imidazole derivatives and related compounds. 3. Regioselective glycosylation of 4-carbamoylimidazolium-5-olate

In the synthesis of glycosyl derivatives of 4-carbamoylimidazolium-5-olate ( 2 ) by the silyl-Hilbert-Johnson method using trimethylsilyl trifluoromethanesulfonate as catalyst, we obtained N-3 nucleosides 5 as major products and N-1,N-bis-nucleosides 6 as minor ones. The desired N-1 nucleosides 4 were isolated in only low yields. However, the yields of 4 were improved by adding ca. One equivalent of stannic chloride to the silylated 4-carbamoylimidazolium-5-olate ( 3 ). On the basis of nuclear magnetic resonance (¹³C and ²⁹Si) and ultraviolet spectroscopic studies, we verify the formation of σ-complexes between the silylated base 3 and the Lewis acid (stannic chloride or trimethylsilyl trifluoromethanesulfonate), and the propose the structures of these complexes and the reaction mechanism.     

Application of aminopropyltriethoxysilane and <Emphasis Type="Italic">N</Emphasis>-[2-(aminoethyl)-<Emphasis Type="Italic">N</Emphasis>-3-(trimethoxysilyl)propyl]amine to the synthesis of linear and heterocyclic compounds

Reaction of 3-aminopropyltriethoxysilane and N-[2-(aminoethyl)-N-3-(trimethoxysilyl)propyl]-amine and their derivatives with diethylcarbamic acid trimethylsilyl ether and trimetisilylisocyanate proceeds through the stage of formation of intermediate products which under conditions of the synthesis undergo intramolecular (in the case of formation O-silylcarbamates) and intermolecular (in the case of the formation of carbamide trimethylsilyl derivatives) desilylation leading to the cyclic and linear products respectively.     

Structural characterisation of trimethylsilyl-protected DNA bases

The structures of the silylated DNA bases, bis(trimethylsilyl)thymine (1), bis(trimethylsilyl)cytosine (2), bis(trimethylsilyl)adenine (3) and tris(trimethylsilyl)guanine (4), have been determined. 1 is O-silylated and displays no intermolecular interactions. 2 is silylated at both exocylic O, N positions and forms a chain structure through intermolecular NH…O and NH…N hydrogen bonds. 3 contains two SiMe₃ groups, on the exocylic NH and endocyclic N⁹ position, respectively; of two independent molecules in the asymmetric unit, one dimerises through complementary NH…N hydrogen bonds, while the other forms a strained intramolecular hydrogen bond through the same pair of donor and acceptor centres. 4 incorporates N, N, O–SiMe₃ moieties and forms chains via bifurcated CH…O/N hydrogen bonds, while the NH function remains unexploited. The effects of silylation on these pyrimidine and purine ring structures are also discussed in comparison with the native bases.

The structures of the silylated DNA bases, bis-(trimethylsilyl)thymine (1), bis-(trimethylsilyl)cytosine (2), bis-(trimethylsilyl)adenine (3) and tris-(trimethylsilyl)guanine (4), have been determined. While 1 displays no intermolecular interactions. 2 forms a chain structure through intermolecular NH…O and NH…N hydrogen bonds, 3 incorporates two independent molecules in the asymmetric unit, one dimerises through complementary NH…N hydrogen bonds while the other forms a strained intramolecular hydrogen bond through the same pair of donor and acceptor centres and 4 forms chains via bifurcated CH…O/N hydrogen bonds while the NH function remains unexploited.     

Reaction of <Emphasis Type="Italic">N,N</Emphasis>′-bis(trimethylsilyl)dicyandiamide with bis(η<Superscript>5</Superscript>-cyclopentadienylvanadium) dichloride

1,3,5-Tris[bis(η⁵-cyclopentadienyl)chlorovanadium]melamin is prepared in high yield by the reaction of N,N′-bis(trimethylsilyl)dicyandiamide with bis(η⁵-cyclopentadienylvanadium) dichloride in tetrahydrofuran. As side products, trimethylchlorosilane and cyclopentadiene formed. Reaction of N,N′-bis(trimethylsilyl) dicyandiamide with benzoyl chloride results in the formation of tris(benzoyl)melamin.     

Synthesis of the New Types of N‐Unsubstituted Aminomethylenebisorganophosphorus Acids and Their Derivatives

The interaction of trimethylsilyl esters of trivalent organophosphorus acids containing PH and POSiMe₃ groups with hydrochlorides of ethoxymethylene imines is a convenient method for the synthesis of new trimethylsilyl esters of N‐unsubstituted aminomethylenebisorganophosphorus acids with three and four coordinated phosphorus. Also trimethylsilyl trifluoromethanesulfonate as effective catalyst is used for the similar interaction of hydrochlorides of ethoxymethylene imines with tris(trimethylsilyl)phosphite. The corresponding bisorganophosphorus acids and their derivatives are presented.     

Fluorsilylsubstituierte N,N- und N,O-bis(trimethylsilyl)-hydroxylamine

Fluoro- und aminofluoro-silanes react with the lithium salt of N,O-bis(trimethylsilyl)hydroxylamine under LiF elimination and substitution. Alkyl- and amino-fluorosilanes give O-fluorosilyl-N,N-bis(trimethylsilyl)hydroxylamines, arylfluorosilanes give N-fluorosilyl-N,O-bis(trimethylsilyl)hydroxylamines. By the further reaction of O-difluorosilyl-N,N-bis(trimethylsilyl)hydroxylamine with the lithiated hydroxylamine, O,O′-fluoromethylsilyldi[N,N-bis(trimethylsilyl)hydroxylamine] is formed. On heating N-difluorophenylsilyl-N,O-bis(trimethylsilyl)hydroxylamine di[fluorophenylsilyl(methyl)amino]pentamethylsiloxane is formed by methyl group migration. The NMR and mass spectra of the compounds are reported.     

Fluorinated heterocyclic compounds. 4-fluoro-2-pyridone

The uracil analog, 4-fluoro-2-pyridone was synthesized by ether cleavage of 4-fluoro-2-methoxypyridine with trimethylsilyl iodide. Improved procedures for the preparations of 2-methoxypyridine N-oxide hydrochloride and 2-methoxy-4-nitropyridine N-oxide are described.     

Regioselective Deprotection and Acylation of Penta-N-Protected Thermopentamine

The synthesis of the penta-N-protected polyamide 1 (tert-butyl N-{9-allyl-16-azido-13-(trifluoroacetyl)-4-[2-(trimethylsilyl)ethylsulfonyl]-4,9,13-triazahexadecyl]carbamate=tert-butyl N-{3-{{4-{allyl{3-[(3-azidopropyl)(trifluoroacetyl)aminopropyl}amino}butyl}{[2-(trimethylsilyl)ethyl]sulfonyl}amino}propyl}carbamate) is described, a derivative of thermopentamine (PA 3433) containing five independently removable amino-protecting groups. The selective deprotection of the five protecting groups used, i.e., of allyl, azido, (tert-butoxy)carbonyl (Boc), trifluoroacetyl, and [2-(trimethylsilyl)ethyl]sulfonyl (SES), as well as the rapid transamidation reaction of the trifluoroacetyl group yielding secondary amides is discussed. Subsequent acylation with 4-methoxycinnamoyl chloride at each N-atom of the pentamine backbone is achieved. For the acylation of the terminal N-atom the azido group is replaced by a (2,2,2-trichloro-1,1-dimethylethoxy)carbonyl (Tcboc) group.     

A New Method of Bile Acid Silylation for Their GLC–MS Analysis

The trimethylsilyl (TMS) derivatives of a mixture of nine bile acids (six free and three conjugated), namely lithocholic, deoxycholic, chenocholic, cholic, hyodeoxycholic, ursodeoxycholic, glycodeoxycholic, glycocholic and glycochenodeoxycholic acids, have been prepared by a new, simple, efficient derivatization procedure, based on the use of a mixture of N -methyl- N -trimethylsilyl-1,1,1- trifluoroacetamide and 1-(trimethylsilyl)imidazole, as the silylating agent. The above-mentioned bile acids were completely trimethylsilylated on all hydroxyl and carboxyl groups whereas carbonyl and amino groups remained untouched.