The reaction of chloromagnesium bis(2,3,5,6-tetrachlorophenyl)copper with butyllithium

Chloromagnesium bis(2,3,5,6-tetrachlorophenyl)copper, prepared from two equivalents of 2,3,5,6-tetrachlorophenylmagnesium chloride and one equivalent of copper(I) chloride inTHF, reacts with one equivalent of butyllithium at –78°C to give, subsequent to derivatisation with chlorotrimethylsilane and then with acetyl chloride, (1-acetyl-2,3,5,6-tetrachlorophenyl)trimethylsilane (20%), 1-(trimethylsilyl)-2,3,5,6-tetrachlorobenzene (17%) and 1-acetyl-2,3,5,6-tetrachlorobenzene (34%) along with some trace products. The formation of these products is explained on the basis of the intermediate formation of chloromagnesium bis(1-lithio-2,3,5,6-tetrachlorophenyl)copper, a functionalised cuprate reagent.

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Die Reaktion von Chlormagnesium-bis(2,3,5,6-tetrachlorphenyl) kupfer mit Butyllithium

Zusammenfassung Chlormagnesium-bis(2,3,5,6-tetrachlorphenyl)kupfer, das aus zwei Äquivalenten 2,3,5,6-tetrachlorphenylmagnesiumchlorid und einem Äquivalent Kupfer(I)chlorid inTHF hergestellt wurde, ergab mit einem Äquivalent Butyllithium bei — 78 °C nach Derivatisierung mit Chlortrimethylsilan und dann mit Acetylchlorid folgende Produkte: (1-Acetyl-2,3,5,6-tetrachlorphenyl)trimethylsilan (20%), 1-(Trimethylsilyl)-2,3,5,6-tetrachlorbenzol (17%) und 1-Acetyl-2,3,5,6-tetrachlorbenzol (34%) neben einigen weiteren Produkten in Spuren. Die Bildung der genannten Produkte wird mit Chlormagnesium-bis(1-lithio2,3,5,6-tetrachlorphenyl)kupfer, einem funktionalisierten Cuprat-Reagens, als intermediär gebildeter Verbindung erklärt.

     

Regiospecific Displacement of the C-B Bond of Tris[4-(substituted)furan-3-yl]boroxines with C-Sn Bond and C-O Bond: Syntheses of 3,4-Disubstituted Furans and 4-Substituted-3(2H)-furanones,

Tris[4-(substituted)furan-3-yl]boroxines 2 , prepared from the corresponding 4-(substituted)-3-(trimethylsilyl) furan 1, were converted successfully to 4-(substituted)-3-(tributylstannyl)furans 3 through palladium-catalyzed cross-coupling reactions with tributylstannyl chloride. Palladium-catalyzed cross-coupling reactions of 3 with organohalides afforded 3,4-disubstituted furans 4 . Regiospecific iodination of 4-(trimethylsilyl)-3-((tributylstannyl) furan ( 3a ) gave 4-iodo-3-(trimethylsilyl)furan ( 5 ), which reacted with excess ethyl acrylate under a common Heck-condition to produce 2,3-bis(trans-ethoxycarbonylvinyl)-4-(trimethylsilyl)furan ( 6 ). A thermal 6-electrocyclic reaction followed by dehydration converted 6 into benzo[2,3-6]furan 8 . Oxidation of 2 generated the corresponding 4-substituted-3(2H)-furanones 9 .     

Trimethylsilylverbindungen der Vb-Elemente. I Synthese und Eigenschaften von Trimethylsilylarsanen

Trimethylsilyl Derivatives of Vb-Elements. I. Syntheses and Properties of Trimethylsilylarsanes Chlorotrimethylsilane and ?Na₃As/K₃As”? prepared from a sodium potassium alloy and arsenic powder in dimethoxyethane form tris(trimethylsilyl)arsane 4 in 80 to 90percent; yield. 4 reacts with methyllithium in THF or dimethoxyethane to lithiumbis(trimethylsilyl)arsenide 5 , which crystallizes with two molecules THF – 5a – or one molecule dimethoxyethane – 5b – per formula unit. The latter adduct is dimeric in benzene. In the reaction of 5 with primary and secondary alkyl halides methyl- 1a , ethyl- 1b , isopropyl- 1c , benzyl- 1d , diphenylmethylbis(trimethylsilyl)arsane 1e and bis[bis(trimethylsilyl)arsano]methane 1f are formed. With tert. butyl chloride a β-elimination results in the formation of bis(trimethylsilyl)arsane; in the reaction with chlorodiphenylmethane and dibromoethane an alkali metal-halogen-exchange takes place yielding tetrakis(trimethylsilyl)-diarsane 6 . On heating bis[bis(trimethylsilyl)arsano]dimethylsilane 7 , synthesized from 5 and dichlorodimethylsilane, to 240°C for several days it decomposes to 4 and dodecamethyl-hexasila-tetra-arsa-adamantane 8 . Tert. butyl- 1g and phenylbis(trimethylsilyl)arsane 1h which cannot be obtained from 5 are prepared from primary arsanes via the corresponding dilithium derivatives.     

Synthesis of bromo-, boryl-, and stannyl-functionalized 1,2-bis(trimethylsilyl)benzenes via Diels-Alder or C-H activation reactions

1,2-Bis(trimethylsilyl)benzenes are key starting materials for the synthesis of benzyne precursors, Lewis acid catalysts, and certain luminophores. We have developed efficient, high-yield routes to functionalized 4-R-1,2-bis(trimethylsilyl)benzenes, starting from either 1,2-bis(trimethylsilyl)acetylene/5-bromopyran-2-one (2) or 1,2-bis(trimethylsilyl)benzene (1)/bis(pinacolato)diborane. In the first reaction, 5 (R = Br) is obtained through a cobalt-catalyzed Diels-Alder cycloaddition. The second reaction proceeds via iridium-mediated C-H activation and provides 8 (R = Bpin). Besides its use as a Suzuki reagent, compound 8 can be converted into 5 with CuBr(2) in i-PrOH/MeOH/H(2)O. Lithium-bromine exchange on 5, followed by the addition of Me(3)SnCl, gives 10 (R = SnMe(3)), which we have applied for Stille coupling reactions. A Pd-catalyzed C-C coupling reaction between 5 and 8 leads to the corresponding tetrasilylbiphenyl derivative. The bromo derivative 5 cleanly undergoes Suzuki reactions with electron-rich as well as electron-poor phenylboronic acids.     

Über die Synthese von Tris(trimethylsilyl)silyl-kalium, -rubidium und -caesium und die Molekülstrukturen zweier Toluolsolvate

About the Synthesis of Tris(trimethylsilyl)silyl Potassium, Rubidium and Cesium and the Molecular Structures of two Toluene Solvates . Solventfree tris(trimethylsilyl)silyl potassium ( 1 ), rubidium ( 2 ) and cesium ( 3 ) are obtained by the reaction of the zink group bis[tris(trimethylsilyl)silyl] derivatives with the appropriate alkali metal in n-pentane. Addition of benzene or toluene to the colourless powders yields deeply coloured solutions. From these solutions single crystals of tris(trimethylsilyl)silyl rubidium—toluene (2/1) ( 2 a ) and tris(trimethylsilyl)silyl cesium—toluene (2/3) ( 3 a ) suitable for X-ray structure analysis are iso- lated [ 2a : orthorhombic; P2₁2₁2₁; a = 1 382.1(3); b = 1 491.7(5); c = 2 106.3(6) pm; Z = 4 (dimers); 3a : orthorhombic; P2₁2₁2₁; a = 2 131.0(6); b = 2 833.1(2); c = 925.2(2) pm; Z = 4 (dimers)]. The central structure moieties are folded four-membered Rb₂Si₂ and Cs₂Si₂ rings, respectively. Small Si? Si? Si angles (100 to 104°) on the one hand and extreme highfield ²⁹Si-NMR shifts of the central silicon atoms on the other hand indicate a strong charge transfer from the alkali metal atoms to the tris(trimethylsilyl)silyl fragments, i.e. mainly ionic interactions between alkalimetal and silicon atoms.     

2-(N-三氟乙酰-N-三甲基硅烷基)氨基-3-三甲基硅烷氧基-羧酸三甲基硅烷酯和2-(N-三氟乙酰)-2,3-脱氢氨基酸的合成

近十几年来,N原子上带有保护基团的α,β脱氢氨基酸及其衍生物的新的合成方法,由于发现这类化合物存在于微生物、低等植物和海生动物体中而具有重要意义。另     

Synthese,Eigenschaften und Struktur von Amin-Addukten der Lithium-tris[bis(trimethylsilyl)methyl]zinkate

Synthesis, Properties, and Structure of the Amine Adducts of Lithium Tris[bis(trimethylsilyl)methyl]zincates . Bis[bis(trimethylsilyl)methyl]zinc and the aliphatic amine 1,3,5-trimethyl-1,3,5-triazinane (tmta) yield in n-pentane the 1:1 adduct, the tmta molecule bonds as an unidentate ligand to the zinc atom. Bis[bis(trimethylsilyl)methyl]zinc · tmta crystallizes in the triclinic space group P1 with {a = 897.7(3); b = 1 114.4(4); c = 1 627.6(6) pm; α = 90.52(1); β = 103.26(1); γ = 102.09(1)°; Z = 2}. The central C₂ZnN moiety displays a nearly T-shaped configuration with a CZnC angle of 157° and Zn? C bond lengths of 199 pm. The Zn? N distances of 239 pm are remarkably long and resemble the loose coordination of this amine; a nearly complete dissociation of this complex is also observed in benzene. The addition of aliphatic amines such as tmta or tmeda to an equimolar etheral solution of lithium bis(trimethylsilyl)methanide and bis[bis(trimethylsilyl)methyl]zinc leads to the formation of the amine adducts of lithium tris[bis(trimethylsilyl)methyl]zincate. Lithium tris[bis(trimethylsilyl)methyl]zincate · tmeda · 2 Et₂O crystallizes in the orthorhombic space group Pbca with {a = 1 920.2(4); b = 2 243.7(5); c = 2 390.9(5) pm; Z = 8}. In the solid state solvent separated ions are observed; the lithium cation is distorted tetrahedrally surrounded by the two nitrogen atoms of the tmeda ligand and the oxygen atoms of both the diethylether molecules. The zinc atom is trigonal planar coordinated; the long Zn? C bonds with a value of 209 pm can be attributed to the steric and electrostatic repulsion of the three carbanionic bis(trimethylsilyl)methyl substituents.     

Reactions of Tris(acetonitrile)tricarbonylchromium with Trimethylsilylarenes

The reactions of tris(acetonitrile)tricarbonylchromium 1 with trimethylsilyl derivatives 2–5 of phenalene, indene, 1,2-dihydronaphthalene and trans-β-methylstyrene gave products 10-13, respectively, containing no trimethylsilyl groups. The reactions of 1 with trimethylsilyl derivatives 6–8 of benzene, toluene and cycloheptatriene gave products 14–16, respectively, containing trimethylsilyl groups. The reaction of 1 with 1,2-bis(trimethylsily-1,2-dihydro)naphthalene 9 gave product 17 in which only trimethylsilyl at the allylic position was cleaved. Compound 10 crystallizes in the orthorhombic system, space group Pbca, with a = 12.228(4), b = 14.288(1), c = 15.128(3) Å, Z = 8, R_F= 0.046, and R_w = 0.047. X-ray crystallographic data confirm that the Cr(CO)₃ moiety is bonded to phenalene in a η⁶-mold.     

Lithium fluoroarylamidinates: syntheses, structures, and reactions

Lithium fluoroarylamidinates [(Ar(F)C(NSiMe(3))(2)Li)(n).xD] (Ar(F) = 4-CF(3)C(6)H(4), n = 2, D = OEt(2), x = 1 (2a); n = 1, D = TMEDA, x = 1 (4a); Ar(F) = 2-FC(6)H(4), n = 2, D = OEt(2), x = 1 (2b); Ar(F) = 4-FC(6)H(4), n = 2, D = OEt(2), x = 2 (2c); Ar(F) = 2,6-F(2)C(6)H(3), n = 2, D = OEt(2), x = 1 (2d); n = 2, D = 2,6-F(2)C(6)H(3)CN, x = 2 (3d); Ar(F) = C(6)F(5), n= 2, D = OEt(2), x = 1 (2e), n = 1, D = TMEDA, x = 1 (4e); n = 1, x = 2, D = OEt(2) (5e); D = THF (6e)) were prepared by the well-known method from LiN(SiMe(3))(2) and the corresponding nitrile in diethyl ether or by addition of the appropriate donor D to the respective diethyl ether complexes. Depending on the substituents at the aryl group and on the donors D, three different types of structures were confirmed by X-ray crystallography. Hydrolysis of 2e gave C(6)F(5)C(NSiMe(3))N(H)SiMe(3) (7e) and C(6)F(5)C(NH)N(H)SiMe(3) (8e). The lithium fluoroarylamidinates 2a-2d react with Me(3)SiCl to give the corresponding tris(trimethylsilyl)fluoroarylamidines Ar(F)C(NSiMe(3))N(SiMe(3))(2) (9a-9d). Attempts to prepare C(6)F(5)C(NSiMe(3))N(SiMe(3))(2) from 2e and Me(3)SiCl failed; however, the unprecedented cage [[C(6)F(5)C(NSiMe(3))(2)Li](4)LiF] (10e) in which a fluoride center is surrounded by a distorted trigonal bipyramid of five Li atoms was obtained from this reaction.     

Metallderivate von Molekülverbindungen. V. Synthese und Struktur von Hexakis{lithium-[tris(trimethylsilyl)silyl]tellanid}—Cyclopentan (1/1)

Metal Derivatives of Molecular Compounds. V. Synthesis and Structure of Hexakis{lithium-[tris(trimethylsilyl)silyl]tellanide}—Cyclopentane (1/1) . Lithium [tris(trimethylsilyl)silyl]tellanide—DME (1/1) [1 b] prepared from lithium tris(trimethylsilyl)silanide—DME (2/3) [3] and tellurium, reacts with hydrogen chloride in toluene to form [tris(trimethylsilyl)silyl]tellane ( 1 ) [1 b]. Subsequent metalation of this compound with lithium n-butanide gives lithium [tris(trimethylsilyl)silyl]tellanide ( 2 ) free of coordinating solvent. Pale yellow crystals are obtained from cyclopentane solution. An X-ray structure determination {P1 ; a = 1 558.5(7); b = 1 598.4(8); c = 1 643.5(6) pm; α = 117.64(4); β = 91.63(3); γ = 117.19(3)°; Z = 1; R = 0.032} shows them to be the (1/1) packing complex ( 2 ′) of hexakis{lithium-[tris(trimethylsilyl)silyl]tellanide} and disordered cyclopentane molecules —{Li? Te? Si[Si(CH₃)₃]₃}₆ · C₅H₁₀.     

Heteroleptische Diorganylzink-Verbindungen mit einem Bis(trimethylsilyl)phosphanido-Substituenten

Heteroleptic Diorganylzinc Compounds with a Bis(trimethylsilyl)phosphido Substituent Dialkylzinc ZnR₂ (Me, Et, iso-Pr, nBu, tBu, CH₂SiMe₃) reacts with one equivalent of bis(trimethylsilyl)-phosphine in carbohydrates to the heteroleptic compounds RZnP(SiMe₃)₂; dependent from the steric demand of the alkyl group R the derivatives are dimeric or trimeric in solution as well as in the solid state. Monomeric bis(trimethylsilyl)phosphido-tris(trimethylsilyl)methylzinc yields from the reaction of lithium tris(trimethylsilyl)methanide and lithium bis(trimethylsilyl)phosphide with zinc(II) chloride. Bis(trimethylsilyl)phosphido-methylzinc crystallizes in the orthorhombic space group P2₁2₁2₁ with {a = 1 007.6(1); b = 1 872.3(3); c = 2 231.0(4) pm; Z = 4} as a trimeric molecule with a central cyclic Zn₃P₃ moiety in the twist-boat conformation. Bis(trimethylsilyl)phosphido-n-butylzinc, that crystallizes in the orthorombic space group Pben with {a = 1 261.7(2); b = 2 253.0(4); c = 1 798.9(2) pm; Z = 4}, shows a simular central Zn₃P₃ fragment. The sterically more demanding trimethylsilylmethyl substituent leads to the formation of a dimeric molecule of bis(trimethylsilyl)phosphido-trimethylsilylmethylzinc {monoklin, P2₁/c; a = 907.2(4); b = 2 079.8(8), c = 1 070,2(3) pm; β = 103,48(1)°; Z = 2}. Bis(trimethylsilyl)phosphido-iso-propylzinc shows in solution a temperature-dependent equilibrium of the dimeric and trimeric species; the crystalline state contains a 1:1 mixture of these two oligomers {orthorhombisch; Pbca; a = 1 859.0(3); b = 2 470.9(2); c = 3 450.7(3) pm; Z = 8}. The Zn? P bond lengths vary in a narrow range around 239 pm, the Zn? C distances were found between 196 and 203 pm.     

Bis[tris(trimethylsilyl)silyl]zink, -cadmium und -quecksilber,schwingungsspektroskopische Daten und Strukturanalysen

Bis[tris(trimethylsilyl)silyl] Zinc, Cadmium, and Mercury – a Structural Study by IR and Raman Spectroscopy and X-Ray Analyses Raman and FT-IR spectra of bis[tris(trimethylsilyl)silyl] zinc ( 1 ), cadmium ( 2 ) and mercury ( 3 ) were recorded. The vibrational data are in agreement with either D_3h or a D_3d symmetry. The latter had been shown to be the correct one at least for the solid state by X-ray diffraction experiments. All three compounds crystallize isomorphically in the triclinic centrosymmetric space group P1 . [ 2 (T = 293 K): a = 9.4388(11); b = 9.744(2); c = 12.926(2); α = 68.200(12); β = 71.971(10); γ = 60.925(10); Z = 1; (T = 173 K): a = 9.336(6); b = 9.585(5); c = 12.488(8); α = 68.77(4); β = 72.28(4); γ = 62.06(4); 3 : a = 9.467(2); b = 9.749(2); c = 12.885(2); α = 67.840(14); β = 71.510(14); γ = 60.890(14); Z = 1]. The Hg—Si bondlength in 3 was found to be 246.9(2)pm, somewhat shorter then in all disilylmercury derivatives investigated sofar and even shorter than the Cd—Si bond in 2 (250.4(1)pm). Bondlengths and angles within the tris(trimethylsilyl)silyl group are virtually equal in all three group 12 derivatives and lie in the expected range.     

Preparation and structural characterisation of methoxybis(trimethylsilyl)silyl potassium and its condensation product

Depending on the conditions the reaction of tris(trimethylsilyl)methoxysilane (1) with potassium tert-butoxide either in benzene and in the presence of 18-crown-6 or in THF gives either the crown ether adduct of potassium-methoxybis(trimethylsilyl)silane (2), or 2-methoxytetrakis(trimethylsilyl)disilanyl potassium (3).     

Die Kristall- und MolekülStruktur von N,N′-Bis-(trimethylsilyl)-oximidsäure-bis(trimethylsilyl)-ester

The Crystal and Molecular Structure of N,N′-Bis(trimethylsilyl) Oximidic Acid Bis (trimethylsilyl) Ester The X-ray structure analysis of the reaction product of oxalyl chloride with sodium bis(trimethylsilyl) amide formulated by PUMP and ROCHOW as N,N′-bis(trimethylsilyl) oximidic Acid bis (trimethylsilyl) ester shows that the suggested structure is correct for the solid state. The compound crystallizes in the space group P1 with a = 9.948(4), b = 6.612(3), c = 10.370(4) Å, α = 88.87(6), β = 116.95(4), γ = 98.23(6)°, and Z = 1. The molecule manifests symmetry 1 .     

Photochemical and Acid-Catalyzed Rearrangements of 4-Carbomethoxy-4-methyl-3-(trimethylsilyl)-2,5-cyclohexadien-1-one

The synthesis of 4-carbomethoxy-4-methyl-3-(trimethylsilyl)-2,5-cyclohexadien-1-one (1) in 60% overall yield from benzaldehyde is described. Irradiation (366 nm) of 1 in benzene solution gave products of type A photorearrangement; e.g., diastereomers of the 4-(trimethylsilyl)- and 5-(trimethylsilyl)bicyclo[3.1.0]hex-3-en-2-ones 8 and 9. Bicyclohexenones 9a and 9b could not be isolated, but underwent acid-catalyzed protiodesilylative rearrangements on attempted chromatography (silica gel) to give a 1:1 mixture of (E)- and (Z)-4-(carbomethoxymethylmethylene)cyclopent-2-en-1-ones 12 and 13. Irradiation (366 nm) of either 12 or 13 resulted in photoisomerization to a photostationary state that was also a 1:1 mixture. Irradiation of 8a or 8b gave equivalent mixtures of phenols 14 and 15 by way of the type B oxyallyl zwitterion 17. The available experimental evidence suggests that both 9a and 9b undergo regiospecific photorearrangement to phenol 16 with no trace of 3-methyl-4-carbomethoxyphenol (19), the product of ipso substitution of the Me(3)Si group at C(4). Phenol 15 was isolated in 65% yield from the photoreaction of 1 in benzene with 20 equiv of CF(3)CO(2)H. The acid-catalyzed rearrangement of 1 to 3-carbomethoxy-4-methylphenol (21) occurs in 91% yield by way of CO(2)Me group rearrangement to C(3) to give the Me(3)Si-stabilized carbocation 23.     

Palladium-catalyzed cyanation of propargylic carbonates with trimethylsilyl cyanide

[reaction: see text]An equimolar mixture of propargylic carbonate (1) and trimethylsilyl cyanide (2) in THF under reflux affords cyanoallene (3) in the presence of a catalytic amount (5 mol %) of Pd(PPh3)4. In the reaction, the trimethylsilyl moiety of 2 effectively traps the leaving group of 1. The use of 2 in excess (6 equiv) provides dicyanated products (7 or 8) in high yields.     

1,5,2,4,6,8-Dithiatetrazocine. Synthesis, computation, crystallography and voltammetry of the parent heterocycle

The prototypal 1,5,2,4,6,8-dithiatetrazocine has been synthesized for the first time by two routes: reaction of 1,2,3,5-dithiadiazolium chloride with N,N,N'-tris(trimethylsilyl)formamidine in acetonitrile and reaction of 1,2,3,5-dithiadiazolyl radical with dioxygen in solution. Yields are low but single crystals could be obtained for an X-ray crystal structure determination which shows it to have the planar delocalized structure predicted by B3LYP/6-311+G(2d,p) hybrid DFT calculations. The crystal structure is strongly reminiscent of that of benzene in the same Pbca space group. Aromaticity is demonstrated by a (1)H NMR chemical shift of +9.70 ppm indicative of diamagnetic ring shielding and an intense low-energy optical absorption with λ(max) = 349 nm (MeOH). The voltammetric behaviour of the title compound is compared with that of 1,3λ(4)δ(2),5,2,4-trithiadiazepine; both resist electrochemical oxidation and reduction over a wide potential range as is typical for aromatic heterocycles.     

Linear and cyclic polysilanes containing the bis(trimethylsilyl)amino group: synthesis,reactions, and spectroscopic characterization

The reaction of linear (Si(n)Cl(2)(n)(+2); n = 3-5) and cyclic (Si(5)Cl(10)) perchloropolysilanes with 1 or 2 equiv of LiN(SiMe(3))(2) results in the formation of the bis(trimethylsilyl)amino derivatives (Me(3)Si)(2)NSi(3)Cl(7) (1), (Me(3)Si)(2)NSi(4)Cl(9) (2), (Me(3)Si)(2)N(SiCl(2))(n)N(SiMe(3))(2) (n = 3, 4; n = 4, 5; n = 5, 6), cyclo-(Me(3)Si)(2)NSi(5)Cl(9) (7), and cyclo-[(Me(3)Si)(2)N](2)Si(5)Cl(8) (8). 1-8 easily can be hydrogenated with LiAlH(4) to give the corresponding amino and diamino polysilanyl hydrides. The monosubstituted and cyclic compounds 1, 2, 7, and 8 additionally afford Si-Si bond scission products, which cannot be separated in all cases. Chloro- and dichloro derivatives of Si(3)H(8), n-Si(4)H(10), and n-Si(5)H(12) are obtained from the corresponding aminosilanes and dry HCl. All compounds were characterized by standard spectroscopic techniques. For Si-H derivatives the coupled (29)Si NMR spectra were analyzed to obtain an unequivocal structural proof.     

One-Pot Synthesis of N-Boc-2, 5-bis(trimethylsilyl)pyrrolidine

Since Daly reported the structure of epibatidine and its potent analgesic activity in 19921, study on the synthesis of epibatidine and its derivatives and relationships between the structure and activity of epibatidine has received much attention2. During the course of our research for the synthesis of epibatidine derivatives, N-boc-2, 5-bis(trimethylsilyl)pyrrolidine 4 was used as the key intermediate to construct the skeleton of epibatidine via the 1, 3-dipolar cycloaddition (Scheme 1). Ac…     

Synthesis and chemistry of some pyridazine nucleosides related to certain 5-substituted pyrimidine nucleosides

Condensation of 3,4-dichloro-6-[(trimethylsilyl)oxy] pyridazine ( 3 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β- D -ribofuranose ( 4 ), by the stannic chloride catalyzed procedure, has furnished 3,4-dichloro-1-(2,3,5-tri-O-benzoyl-β- D -ribofuranosyl) pyridazin-6-one ( 5 ). Nucleophilic displacement of the chloro groups and removal of the benzoyl blocking groups from 5 has furnished 3-chloro-4-methoxy-, 3,4-dimethoxy-, 4-amino-3-chloro-, 3-chloro-4-methylamino-, 3-chloro-4-hydroxy-, and 4-hydroxy-3-methoxy-1-β- D -ribofuranosylpyridazin-6-one. An unusual reaction of 5 with dimethylamine is reported. Condensation of 4,5-dichloro-3-nitro-6-[(trimethylsilyl)oxy]pyridazine with 4 yielded 4,5-dichloro-3-nitro-1-(2,3,5-tri-O-benzoyl-β- D -ribofuranosyl)pyridazin-6-one ( 24 ). Nucleophilic displacement of the aromatic nitro groups from 24 is discussed. Condensation of 3 with 3,5-di-O-p-toluoyl 2-deoxy- D -erythro-pentofuranosyl chloride ( 28 ) afforded an α, β mixture of 2-deoxy nucleosides. The synthesis of certain 3-substituted pyridazine 2′-deoxy necleosides are reported.