Mono-, di-, and tricoordinated phosphorus attached to a N-N unit: an experimental and theoretical study

N,N',N'-[Tris(trimethylsilyl)]hydrazino-diphenylphosphane, (TMS)2 N-(TMS)N-PPh2 (1), and N,N',N'-[tris(trimethylsilyl)]hydrazino-phenyl(chloro)phosphane, (TMS)2 N-(TMS)N-P(Cl)Ph2 (2), were obtained in the reaction of bis-[lithium-tris(trimethylsilyl)hydrazide] with Ph(n)PCl(3 - n) (n = 1, 2). The structure and bonding of both species are discussed on the basis of experimentally observed (X-ray, Raman, NMR, and MS) and theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). Oxidation with sulfur and selenium results in the formation of (TMS)2 N-(TMS)N-P(S)Ph2 (4), (TMS)2 N-(TMS)N-P(Se)Ph2 (5), (TMS)2 N-(TMS)N-P(S)Ph(Cl) (6), and (TMS)2 N-(TMS)N-P(Se)Ph(Cl) (7). Moreover, the thermal decomposition of N,N',N'-[tris(trimethylsilyl)]hydrazine-dichlorophosphane, (TMS)2 N-(TMS)N-PCl2 (3) and the reaction with magnesium have been investigated. The formation and molecular structure of the novel MgCl2(THF)2 x 2Mg[(TMS)NP(O)2 N(TMS)2](THF) (8) salt containing the hitherto unknown (TMS)NP(O)2 N(TMS)2(2-) anion are discussed. DFT calculations (B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p)) are used to evaluate the bonding, ground-state structures, and energy landscape for the different isomers of 3: the thermodynamics and kinetics of the successive elimination of chlorotrimethylsilane (TMS-Cl) resulting in the formation of covalent azide analogues such as TMS-PNN or TMS-NNP.     

Disilylation of N-(2-Halophenyl)-2-phenylacrylamides with hexamethyldisilane via trapping the spirocyclic palladacycles

The palladium-catalyzed disilylation of the spirocyclic palladacycles with hexamethylaisilane has been realized. The key spirocyclic palladacycles are generated from N-(2-haloaryl)-2-arylacrylamide via intramolecular Heck reaction and followed remote C-H activation. A range of 3-((trimethylsilyl)methyl)-3-(2-(trimethylsilyl)phenyl)indolin-2-ones are obtained in good to excellent yields from readily available starting material under mild conditions.     

Reaction of N,N-Dichlorosulfonamides with Ethynyl(trimethyl)silane

Russian Journal of Organic Chemistry - Ethynyl(trimethyl)silane reacted with N,N-dichloroarenesulfonamides to give unstable N-[2,2-di­chloro-2-(trimethylsilyl)ethylidene]arenesulfonamides...     

Conformational, steric and electronic effects on the site- and chemoselectivity of the metal-catalyzed reaction of N-bis(trimethylsilyl)methyl, N-(2-indolyl)methyl α-diazoamides

The Rh(II)- and Cu(II)-catalyzed reactions of N-bis(trimethylsilyl)methyl, N-(2-indolyl)methyl α-diazoamides are investigated to delineate how conformational, steric and electronic factors influence the site- and chemoselectivity of the metallocarbenoid reaction. The N-bis(trimethylsilyl)methyl (N-BTMSM) group is found to be essential in promoting the metallocarbenoid reaction at the N-(2-indolyl)methyl moiety as well as providing subtle but effective conformational influence about the amide N-C(α) sigma bond in diazoamides carrying an N-C(α) alkoxymethyl side-chain, to afford excellent site- and chemoselectivity. In general, the metal-catalyzed reactions are found to favor metallocarbenoid addition to the indole C(2)-C(3) double bond over C-H insertion to give cyclopropanated products (tetracyclic γ-lactams); however, chemoselectivity is also affected by steric effects, as revealed in the N-[2-(3-methylindolyl)]methyl diazoamides, and to some extent by the nature of the catalyst employed, as seen in the N-C(α)-alkoxymethyl diazoamides. The tetracyclic γ-lactams are found to rearrange to give good to high yields of the tricyclic indole derivatives under the metallocarbenoid reaction conditions or under acidic conditions. The propensity of the tetracyclic γ-lactams to undergo rearrangement is found to be dependent on the nature of the α-substituent on the original diazo carbon and the indole N-substituent.     

Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Regioselective protection at N-2 and derivatization at C-3 of indazoles

Indazoles are regioselectively protected at N-2 by a 2-(trimethylsilyl)ethoxymethyl (SEM) group using novel conditions. The SEM group can efficiently direct regioselective C-3 lithiation, and the resulting nucleophile can react with a wide range of electrophiles to generate novel indazole derivatives. The SEM group can be removed by treatment with TBAF in THF or aqueous HCl in EtOH.     

Lithiation of trimethylsilyl substituted acetamide derivatives : Addition to carbonyl compounds

The lithio anions of N,O-bis(trimethylsilyl)acetamide and N-(trimethylsilyl)-N-methylacetamide were prepared and reacted with several carbonyl compounds to form β hydroxy acetamide and N-methylacetamide derivatives.     

A Convenient Synthesis of Aminomethylphosphonous Acid

Aminomethylphosphonous acid has been prepared in exellent yield by alkylation of bis(trimethylsilyl) ethoxycarbonylphosphonite 2 with N-(bromomethyl)phthalimide 1, followed by acidic removal of protecting groups.     

Preparation of perhydroisoquinolines via the intramolecular Diels-Alder reaction of N-3,5-hexadienoyl ethyl acrylimidates: a formal synthesis of (+/-)-reserpine

The intramolecular Diels-Alder reaction of N-3,5-hexadienoyl ethyl acrylimidates provides an efficient method for the synthesis of cis-fused hexahydroisoquinolones. As a demonstration of the stereochemical control offered by this cycloaddition, two approaches to the construction of the DE rings of reserpine are reported. In the second entry, N-((4-(trimethylsilyl)ethoxymethoxy)methyl-6-benzyloxy-3Z,5E-hexadienoyl)-1-aza-2-ethoxy-1,3-butadiene (40) undergoes cycloaddition to produce as the major product (4aS,7R,8aS)-7-benzyloxy-5-((2-trimethylsilyl)ethoxymethoxy)methyl-3,4,4a,7,8,8a-hexahydroisoquinol-3-one (41). Cycloadduct 41 is then stereospecifically elaborated to (4aS,5S,6R,7R,8aR)-6-methoxy-5-methoxycarbonyl-7-(3,4,5-trimethoxy)benzoyldecahydroisoquinoline-2-carboxylic acid methyl ester (3), a key intermediate previously transformed to reserpine.     

合成α 酮酸的新方法

本文报道了一种新的简便的合成α-酮酸(4)的新方法. 用三氟乙酸酐在4-N,N-二甲基氨基吡啶催化下在二氯乙烷溶剂中和易于制得的2,3-二(三甲基硅氧基)羧酸三甲基硅酯(1)反应生成2,3-二(三氟乙酰羧酸三甲硅酯(2). 向反应混合物中加入吡啶生成2-三氟乙酰氧基-2-烯酸(3). 分别用氢氧化钾水溶液和盐酸处理3得产物4 .     

One-pot multistep Bohlmann-Rahtz heteroannulation reactions: synthesis of dimethyl sulfomycinamate

[reaction: see text] The synthesis of dimethyl sulfomycinamate, the acidic methanolysis product of the sulfomycin family of thiopeptide antibiotics, from methyl 2-oxo-4-(trimethylsilyl)but-3-ynoate is achieved in a 2,3,6-trisubstituted pyridine synthesis that proceeds with total regiocontrol in 13 steps by the Bohlmann-Rahtz heteroannulation of a 1-(oxazol-4-yl)enamine or in 12 steps and 9% yield by three-component cyclocondensation with N-[3-oxo-3-(oxazol-4-yl)propanoyl]serine and ammonia in ethanol.     

Darstellung und Einkristall-Strukturanalyse von Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)imidazol]dititan-Chloroform (1/2) [Ti2Cl8(C6H12N2Si)2] · 2 CHCl3

Synthesis and Crystal Structure Determination of Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)imidazol]dititanium Chloroform (1/2) Hexachloro-μ-dichloro-bis[N-(trimethylsilyl)-imidazol]dititanium chloroform (1/2) 1 has been prepared by the reaction of titanium tetrachloride with N-trimethylsilylimidazole (NTMSI) in chloroform solution as orange crystals. The structure consists of two distorted TiCl₅N octahedrons, which are connected by two chlorine atoms via common edges to a centrosymmetric dimer [Ti₂Cl₈(NTMSI)₂] · 2 CHCl₃. The N-trimethylsilylimidazole ligands each are located at one axial position of each octahedron, whereas the equatorial positions are occupied by the chloro ligands. The results presented are discussed assuming a gradual formation of an 1 : 1 and 1 : 2 adduct.     

Formation of 1-(2-aminophenyl)-5-ethoxy-4-methyl-3-phenylpyrazole and 4-methyl-3-phenylpyrazolo-[5,1-b]benzimidazole via an unusual enzotriazole ring opening

Successive treatment of N-[(1-ethoxy)alken-2-yl]benzotriazoles VII with butyllithium and trimethylsilyl chloride in TH-Fat — 78°C followed by refluxing in acidic acetone generated ring-opened 1-(2-aminophenyl)-5-ethoxy-4-methyl-3 phenylpyrazole VIII and 4-methyl-3 phenylpyrazolo[5, 1-b]benzimidazole IX.Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 775–780, June, 1996. Original article submitted May 14, 1996.     

Suitability of N,O-bis(trimethylsilyl)trifluoroacetamide and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide as derivatization reagents for the determination of the estrogens estrone and 17alpha-ethinylestradiol by gas chromatography-mass spectrometry

This paper describes apreviously unreported problem with the use of N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) to derivatise the natural hormone estrone (E1) and the synthetic estrogen 17alpha-ethinylestradiol (EE2). The resulting trimethylsilyl (TMS) and t-butyldimethylsilyl (TBS) derivatives of EE2 were partially converted to their respective El derivatives. Therefore, these reagents may not be suitable for simultaneous determination of estrogens in environmental samples, which raises questions about the reliability of results from some earlier studies.     

Acyclic stereoselection in the reaction of nucleophilic reagents with chiral N-acyliminium ions generated from N-

Optically active N-[1-(phenylsulfonyl)alkyl]imidazolidin-2-ones react at low temperature in the presence of tin tetrachloride to give acyclic N-acyliminium ions. These electrophilic substrates give addition products upon reaction with pi-nucleophiles. Allyltrimethylsilane affords the corresponding allylated products in good yields and high diastereoselectivity. The stereochemical outcome of this process can be rationalized by taking into account the preference of the intermediate N-acyliminium ion for an E configuration that favors the attack of the nucleophile from the si-si face. Disappointing results are obtained using silyl ketene acetals; conversely trimethylsilyl enol ether of acetophenone gives the corresponding adducts in high diastereoselectivity. The utilization of trimethylsilyl enol ether of 2-acetylfuran is particularly interesting since the corresponding adducts are obtained with good diastereoselectivity and the furan ring could be amenable of further synthetic transformations.     

Über die Reaktion des Tris-(trimethylsilyl)-silyllithiums mit Aceton

On the Reaction of Tris-(trimethylsilyl)-silyl Lithium with Acetone Depending on the reaction conditions tris-(trimethylsilyl)-silyl lithium interacts with acetone to give 2-[bis-(trimethylsilyl)-silyl]-2-[tris-(trimethylsilyl)-silyl]-propane 2 or 2-[bis-(trimethylsilyl)-silyl]-2-(trimethylsioxy)-propane 4 , resp. The formation of 2 and 4 as a result of a 1, 3-Si, O-trimethylsilyl shift is discussed. The structure of 2 , which is characterized by strong restrictions of rotation about the C? Si(SiMe₃)₃ bond, is proved by nmr spectra as well as by conversion of 2 into 2-[chloro-bis-(trimethylsilyl)silyl]-2-[tris-(trimethylsilyl)silyl]-propane 3 .     

BtCH(2)TMS-assisted homologation of carboxylic acids: A safe alternative to the arndt-eistert reaction

One-carbon homologation of carboxylic acids is achieved by (i) treatment of an acyl chloride with 1-[(trimethylsilyl)methyl]-1H-1,2, 3-benzotriazole (BtCH(2)TMS) (1) to afford N-(acylmethyl)benzotriazoles 3a-f, followed by (ii) conversion of 3a-f with triflic anhydride into RC(OTf)=CHBt 4a-f, and (iii) the subsequent reaction of 4a-c with NaOCH(3) followed by 1N HCl to afford esters RCH(2)CO(2)R' 7a-c in overall yields of 50-70%. For the aliphatic compounds 5d-f, treatment of 5d-f with p-toluenesulfonic acid followed by TBAF/THF afforded acids RCH(2)COOH 7d-f.     

Studies on imidazole derivatives and related compounds. 4. Synthesis of O-glycosides of 4-carbamoylimidazolium-5-olate

Ribosylation of trimethylsilyl derivative of 1-(4-nitrobenzyl)-5-carbamoylimidazolium-4-olate ( 5 ) with 1,2,3,5-tetra-O-acetyl-β- D -ribofuranose in the presence of stannic chloride and trimethylsilyl trifluoromethanesulfonate afforded no 5-O-glycosides but N-1 ribosylated compound ( 6 ). However, 5-O-riboside ( 7a ) and its orthoamide derivative ( 8 ) were given by glycosylation of tri-n-butylstannyl derivative of 5 with 2,3,5-tri-O-acetyl-β- D -ribofuranosyl chloride in the presence of silver trifluoromethanesulfonate. This procedure was successfully applied to other sugars and 5-O-glucuronide ( 11 ), a possible metabolite of 1 in vivo, was obtained as one of the 5-O-glycoside derivatives.     

Synthesis of 11C-amides using [11C]carbon monoxide and in situ activated amines by palladium-mediated carboxaminations

[11C]Carbon monoxide at low concentrations, aryl halides and amines were used in the palladium-mediated synthesis of twenty 11C-amides. In the study several approaches to improve the radiochemical yield were explored. Eight of the selected amides were prepared by in situ activation of the amines using lithium bis(trimethylsilyl)amide and the radiochemical yields of these reactions were improved compared to utilising a previous reported method. In the synthesis of 1-[carbonyl-11C]benzoyl-3-methyl-1H-indole (11) from 3-methyl-1H-indole (25), the corresponding organotin-amine was prepared prior to the acylation reaction. In a typical experiment, N-(4-hydroxyphenyl)[carbonyl-11C]acetamide (5) was prepared in 15% radiochemical yield using 4-aminophenol (20) but the yield increased to 63% when the amine was activated by lithium bis(trimethylsilyl)amide.     

Phosphine-mediated dehalogenation reactions of trichloro(N-silyl)phosphoranimines

The reaction of N-(trimethylsilyl)phosphoranimine Cl3P=NSiMe3 (1) with nBu3P or Ph3P yields the N-(dichlorophosphino)phosphoranimines nBu3P=NPCl2 (4a) or Ph3P=NPCl2 (4b), respectively. Detailed studies of this reaction indicate a mechanism that involves the reductive dechlorination of 1 by the tertiary phosphine to yield nBu3PCl2 (5a) or Ph3PCl2 (5b) with the apparent formation of the transient chlorophosphinimine ClP=NSiMe3 (6), followed by condensation of 5a or 5b with 1 to form 4a or 4b and Me3SiCl. Convincing evidence for the proposed mechanism was revealed by studies of the analogous reaction between the N-(triphenylsilyl)phosphoranimine Cl3P=NSiPh3 (8) with nBu3P and Ph3P. These reactions quantitatively generated 5a and 5b and also allowed the correspondingly more stable chlorophosphinimine ClP=NSiPh3 (10) to be identified.