Photochemisches Verhalten von 1- und 2-alkylierten 1, 2-Dihydronaphthalinen bei tiefen Temperaturen

The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d₆– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2].     

Aromatische [1,5s]-sigmatropische H-Verschiebungen in Arylallenen

1-Mesityl allene ( 1 ), 1-mesityl-3-methyl allene ( 2 ) and 1-mesityl-3,3-dimethyl allene ( 3 ) rearrange thermally at 150–190° in decane via [1,5s]sigmatropic H-shifts to yield the o-quinodimethanes 4 , which cyclise to give the 1,2-dihydronaphthalenes 5 and 6 and/or undergo [1,7 a]sigmatropic H-shifts to give 1-mesityl-(Z)-buta-1, 3-dienes (Z)- 7 and (Z)- 8 , respectively (Schemes 1,3,4 and 5) in almost quantitative yields. The activation parameters of these isomerisations are given in Table 1. 1-Mesityl-1-methyl allene ( 9 ) isomerises at 190° to give 4,5,7-trimethyl-1,2-dihydronaphthalene ( 17 ) in 50% yield (Scheme 6). 2′-Isopropylphenyl allene ( 10 ) in decane rearranges at 170° to 1-(Z)-propenyl-2-isopropenyl-benzene ((Z)- 19 , Scheme 7). Deuterium labelling experiments show that the rate determining step is an aromatic [1,5s]sigmatropic hydrogen shift from an sp³- to an sp-hybridised carbon atom. The primary kinetic isotopic effect (k_H/k_D) is 3.45, while the secondary βisotopic effect is 1.20 (Scheme 7 and Table 2).     

Synthesis and dehydration reaction of 1-(4-benzyloxyphenyl)-6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphth-2-ol: possible intermediate of Lasofoxifene

The paper deals with a simple and sufficient synthesis of key precursor of Lasofoxifene. The 1-(4-benzyloxyphenyl)-6-methoxy-2-phenyl-3,4-dihydronaphthalene was prepared by a sequence of five reactions steps: first 1-(4-benzyloxyphenyl)-6-methoxy-3,4-dihydronaphthalene was prepared (70%), and this was quantitatively epoxidized to 7b-[4-(benzyloxy)phenyl]-5-methoxy-1a,2,3,7b-tetrahydronaphtho[1,2-b]oxirene. Catalytic (ZnI₂) isomerization of the epoxide gave 1-(4-benzyloxyphenyl)-6-methoxy-1,2,3,4-tetrahydronaphthalen-2-one (75%). Its subsequent reaction with phenylmagnesium bromide gave 1-(4-benzyloxyphenyl)-6-methoxy-2-phenyl-1,2,3,4-tetrahydro-2-naphthol (87%). Acid-catalysed dehydration of this alcohol by polyphosphoric acid (25°C) provides 1-(4-benzyloxyphenyl)-6-methoxy-2-phenyl-1,4-dihydronaphthalene (80%). Dehydration in the system of acetic anhydride/polyphosphoric acid gives 1-(4-benzyloxyphenyl)-6-methoxy-2-phenyl-3,4-dihydronaphthalene (66%).     

Säurekatalysierte Umsetzungen von 2- Vinylanilin-Derivaten mit 1-Benzyl- und 1-Methylpiperidin-4-on: Eine Elegante Synthese Neuer Polycyclischer Indol-Derivate

Acid-Catalyzed Reactions of 2-Vinylaniline Derivatives with 1-Benzyl- and 1-Methylpiperidin-4-one: An Elegant Synthesis of New Polycyclic Indole Derivatives The reaction of 2-vinylaniline derivatives with 1-benzylpiperidin-4-one or 1-methylpiperidin-4-one in toluene at temperatures between 115 and 120° with toluene-4-sulfonic acid as catalyst leads in good yields to a new class of polycyclic indole derivatives (Scheme 1, Table 1). The structure of the new diastereoisomerically pure racemic compounds 1–5 is determined by NMR-spectroscopic methods. A reaction mechanism proceeding via cyclization of enamine 9 , leading to a racemic, tricyclic reactive intermediate 10 , and subsequent intramolecular 1,5-dipolar cyclization as key steps in proposed for the formation of octahydropyrido[4′,3′:4]cyclobut[1,2-b]indoles 1–5 . The scope and limitations of the new method are discussed (see Table 2).     

Five-Membered 2,3-Dioxo Heterocycles: L. Synthesis and Thermolysis of 3-Aroyl- and 3-Hetaroyl-5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxalin-1,2,4-triones

(Z)-3-Phenacylidene- and (Z)-3-hetaroylmethylidene-1-phenyl-1,2,3,4-tetrahydroquinoxalin-2-ones react with oxalyl chloride to give 3-acyl-5-phenyl-1,2,4,5-tetrahydropyrrolo[1,2-a]quinoxaline-1,2,4-triones. Thermolysis of the latter generates acyl(3-oxo-4-phenyl-3,4-dihydroquinoxalin-2-yl)ketenes which are stabilized via [4 + 2]-cyclodimerization followed by [1,3]-acylotropic shift to afford 4-acyl-3-acyloxy-2-(3-oxo-4-phenyl-3,4-dihydroquinoxalin-2-yl)-6-phenyl-5,6-dihydro-1H-pyrido[1,2-a]quinoxaline-1,5-diones.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1101–1108.Original Russian Text Copyright © 2005 by Bozdyreva, Smirnova, Maslivets.     

Synthesis of 1,2-dihydroindolo [1,7-AB] [1,5] benzodiazepines and related structures. A new heterocyclic ring system

The synthesis of the novel 1,2-dihydroindolo [1,7-ab][1,5]benzodiazepine ring system 4 is described. Condensation of 2-fluoronitrobenzene with indoline provided the starting material for the synthesis, 1-(2-nitrophenyl)indoline (1a) in high yield. The nitro group was reduced catalytically and the resulting amino function was acylated to afford the heterocycle percursor amide 3. Refluxing this amide in phosphorus oxychloride brought about a Bischler-Napieralski type cyclodehydration to form the target 1,2-dihydroindolo[1,7-ab][1,5]benzodiazepine ring system. Dehydrogenation of the latter led to the fully aromatic indolo[1,7-ab][1,5]benzodiazepine structure 5, while reduction with sodium borohydride provided the 1,2,6,7-tetrahydroindolo[1,7-ab]-[1,5]benzodiazepine tetracycle 6.     

Thermal decomposition products of methyl 1,5-diphenyl- and 5-methyl-1-phenyl-2,3-diazabicyclo[3.1.0]hex-2-ene-6-exo-carboxylates

Methyl 1,5-diphenyl- and 5-methyl-1-phenyl-2,3-diazabicyclo[3.1.0]hex-2-ene-6-exo-carboxylates at 138°C undergo decomposition via elimination of nitrogen molecule with formation in each case of five products. Two products are methyl 1,3-diphenyl(or 1-methyl-3-phenyl)bicyclo[1.1.0]butane-2-endo- and -exo-carboxylates, and the three others are derivatives of buta-1,3-diene, methyl (Z)-2-benzylidene-3-phenyl(or 3-methyl)but-3-enoate and methyl (E)- and (Z)-3,4-diphenyl(or 4-methyl-3-phenyl)penta-2,4-dienoates. The formation of these products may be rationalized assuming intermediacy of substituted allylcarbene which undergoes both intramolecular cycloaddition and rearrangements involving 1,2-hydride and 1,2-vinyl shifts.     

12. Anil-Synthese. 17. Mitteilung. Über die Herstellung von styryl-derivaten des 2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridins

Preparation of styryl derivatives of 2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine 7-Methyl-2-phenyl- and 2-(3-chloro-4-methylphenyl)-4H-1,2,4-triazolo[1,5-a]-pyridines react with anils of aromatic aldehydes in the presence of dimethyl-formamide and potassium hydroxide at 20–45° to yield the 2-phenyl-7-styryl- and 2-(2-chloro-stilben-4-yl)-4H-1,2,4-triazolo [1,5-a]pyridines respectively (‘Anil Synthesis’). Further, the Schiff's bases derived from o-chloroaniline and 2-(p-formyl-phenyl)- and 7-formyl-2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine yield, with methyl- and with p-tolyl-substituted heterocycles, the corresponding heterocyclic substituted styryl and stilbenyl derivatives.     

Thermisches Verhalten von Mesitylallenen; Beispiel einer aromatischen [1, 5s]-sigmatropischen H-Verschiebung. Vorläufige Mitteilung

Mesitylallene ( 6a ), 1-mesityl-3-methyl-allene ( 6b ) and 1-mesityl-3, 3-dimethylallene ( 6c ) were prepared via dienol-benzene-rearrangements. At 170° 6a isomerises to give 5, 7-dimethyl-1, 2-dihydronaphthalene ( 8 ). Under the same conditions 6b rearranges to give 2, 5, 7-trimethyl-1, 2-dihydronaphthalene ( 10 ; 60%) and cis-1-mesitylbuta-1, 3-diene ( 11 ; 40%) while 6c gives only cis-1-mesityl-3-methyl-buta-1, 3-diene ( 13 ). The allenes undergo first an aromatic [1, 5 s]-sigmatropic H-shift to the o-xylylene derivatives 7, 9 and 12 , which then exhibit disrotatory ring closure to the dihydronaphthalenes or aromatic [1, 7 a]-sigmatropic H-shift to the 1-mesitylbuta-1, 3-dienes.     

Stereoselective synthesis of cis and trans 2-substituted 1-phenyl-3-azabicyclo[3.1.0]hexanes

The Stereoselective synthesis of cis and trans 2-methyl-1-phenyl-3-azabicyclo[3.1.0]hexanes and 1,2-diphen-yl-3-azabicyclo[3.1.0]hexanes from 2-oxo-1-phenyl-3-azabicyclo[3.1.0]hexane is described. The relative stereochemistry of the products was established by nuclear magnetic resonance and molecular modeling studies.     

Über die Synthese von 1-Aryl-und 1-Alkyl-2, 3-dimethyl-chinoxalinium-perchloraten. 2. Mitteilung. Synthese und 1H-NMR.-Spektren von 2,3-Dimethyl-1-phenyl-6-X-chinoxalinium-perchloraten

On the Synthesis of 1-Aryl- and-1-Alkyl-2, 3-dimethyl-quinoxalinium Perchlorates. 2nd Communication

1 1. Mitt.: [1].

. Synthesis and ¹ H-NMR. Spectra of 2, 3-Dimethyl-1-phenyl-6-X-quinoxlinium Perchlorates The synthesis of the title compounds ( 5 ) which have been useful as precursors for a lot of conventional and new-type dyes [2-8] has yet been limited to examples with X?H [2] [3] [11] [15] and with electron-donating [4] [12] or at best slightly electron-accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron-accepting substituents: N-monosubstituted o-phenylendiamines 4 , were condensed with 2, 3-butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products - mostly substituted at position 6 of the quinoxalinium ring - are chracterized by ¹H-NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6 . Correlations of chemical shifts with Hammett's σ_p [18] are given by equations (1)-(5).     

Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C, followed by treatment of the reaction mixture with water gave perfluoro {4-[1-(2-propylphenyl)propylidene]-2,5-cyclohexadien-1-one} together with perfluoro[4b,10-diethylbenzo[a]azulen-7(4bH)-one] resulting from unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzo[a]azulen-6(10H)-ones via elimination of C₂F₅ group from the seven-membered ring or its migration to the benzene ring.     

Photochemistry of N‐(2‐Acylphenyl)‐2‐methylprop‐2‐enamides: Competition between Photocyclization and Long‐Range Hydrogen Abstraction

The photochemical reactions of various ‘N‐methacryloyl acylanilides’ (=N‐(acylphenyl)‐2‐methylprop‐2‐enamides) have been investigated. Under irradiation, the acyl‐substituted anilides 1a – 1c and 1o afforded exclusively the corresponding quinoline‐based cyclization products of type 2 (Table 1). In contrast, irradiation of the benzoyl (Bz)‐substituted anilides 1e – 1h afforded a mixture of the open‐chain amides 4e – 4h and the cyclization products 2e – 2h . Irradiation of the para‐acyl‐substituted anilides 6a – 6e and 6h afforded the corresponding quinoline‐based cyclization products of type 5 as the sole products (Table 2). The formation of the cyclization products 2a – 2c and 2o can be rationalized in terms of 6π‐electron cyclization, followed by thermal [1,5] acyl migration, and that of compounds 3p, 5a – 5e , and 5h can be explained by a 6π‐electron cyclization only. The formation of the open‐chain amides 4e – 4h probably follows a mechanism involving a 1,7‐diradical, C and a spirolactam of type D (Scheme). Long‐range ζ‐H abstraction by the excited carbonyl O‐atom of the benzoyl group on the aniline ring is expected to proceed via a nine‐membered cyclic transition state, as proposed on the basis of X‐ray crystallographic analyses (Fig. 2).     

On Triazoles. XXXII. The reaction of 5-amino-1 H-1,2,4-triazolylcarbothiohydrazides with β- and γ-oxo-esters

5-Amino-lH-1,2,4-triazolylcarbothiohydrazides gave β and γ-oxo-esters in boiling ethanol [1,2,4]triazolo- [1,5-d][1,2,4,6]tetrazepine-5-thiones 3 . Analogously ethyl 2-oxocyclohexanecarboxylate provided a mixture of two diastereomeric spiro derivatives 5 and 6 . At 130°, 2-acetonyl-5-methyl-4,5-dihydro-1,3,4-oxadiazole-5-thione ( 8 ) was formed. Ring closure of 3e (R¹ = CH₃, R² = CH₂CH₂COOEt, Q = morpholino) lead to the isomeric pyrrolo[2,1-g][1,2,4]triazolo[1,5-d][1,2,4,6]tetrazepin-8(11H)-one ( 12 ) and pyrrolo[1,2-f][1,2,4]triazolo-[1,5-d][1,2,4,6]tetrazepin-10(7H)-one ( 13 ) derivatives representing two new ring systems.     

Synthese und Struktur von Lithium-tris(trimethylsilyl)silanid · 1,5 DME

Synthesis and Structure of Lithium Tris(trimethylsilyl)silanide · 1,5 DME Lithium tris(trimethylsilyl)silanide · 1,5 DME 2a synthesized from tetrakis(trimethylsilyl)silane 1 [6] and methyllithium in 1,2-dimethoxyethane , crystallizes in the monoclinic space group P2₁/c with following dimensions of the unit cell determined at a temperature of measurement of ?120 ± 2°C: a = 1 072.9(3); b = 1 408.3(4); c = 1 775.1(5) pm; β = 107.74(2)°; 4 formula units (Z = 2). An X-ray structure determination (R_w = 0.040) shows the compound to be built up from two [lithium tris(trimethylsilyl)silanide] moieties which are connected via a bridging DME molecule. Two remaining sites of each four-coordinate lithium atom are occupied by a chelating DME ligand. The Li? Si distance of 263 pm is considerably longer than the sum of covalent radii; further characteristic mean bond lengths and angles are: Si? Si 234, Li? O 200, O? C 144, O?O (biß) 264 pm; Si? Si? Si 104°, Li? Si? Si 107° to 126°; O? Li? O (inside the chelate ring) 83°. Unfortunately, di(tert-butyl)bis(trimethylsilyl)silane 17 prepared from di(tert-butyl)dichlorsilane 15 , chlorotrimethylsilane and lithium, does not react with alkyllithium compounds to give the analogous silanide.     

Synthesis of pyrido[1,2-a]pyrimido[4,5-d]pyrimidin-5-ones. Cyclization reaction of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid with acetic anhydride

Treatment of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid (X) with acetic anhydride under refluxing conditions afforded 10-hydroxy-2-phenyl-5H-pyrido[1,2-a]-pyrimido[4,5-d]pyrimidin-5-one acetate (IX). The intermediate X was prepared from 4-chloro-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester (V). The reaction of V with the sodium salt of 2-amino-3-hydroxypyridine at room temperature gave 4-(2-amino-3-pyridyloxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester (VI). Treatment of VI with a hot aqueous sodium hydroxide solution and subsequent acidification gave X. Involvement of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecaroboxylic acid ethyl ester (VIII) (Smiles rearrangement product) as an intermediate in the above alkaline hydrolysis reaction of VI to X was demonstrated by the isolation of VIII and its subsequent conversion into X under alkaline hydrolysis conditions. Acetylation of VIII with acetic anhydride in pyridine solution gave 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester acetate (XI), which afforded IX on fusion at 220°. This alternative synthesis of IX from XI supported the structural assignment of IX. Fusion of VI gave 10-hydroxy-2-phenyl-5H-pyrido[1,2-a]pyrimido]4,5-d]pyrimidin-5-one (VII). The latter was also obtained when VIII was fused at 210°. Acetylation of VII with acetic anhydride afforded IX.     

Thermal Reaction of Azulene-1-carbaldehydes with Dimethyl Acetylenedicarboxylate

Azulene-1-carbaldehydes which have Me substituents at C(3) and C(8) and no substituent at C(6) react with excess dimethyl acetylenedicarboxylate (ADM) in decalin at 200° to yield exclusively the Diels-Alder adduct at the seven-membered ring (cf. Scheme 3). The corresponding 1-carboxylates behave similarly (Scheme 4). Azulene-1-carbaldehydes which possess no Me substituent at C(8) (e.g. 11 , 12 in Scheme 2) gave no defined products when heated with ADM in decalin. On the other hand, Me substitutents at C(2) may also assist the thermal addition of ADM at the seven-membered ring of azulene-1-carbaldehydes (Scheme 6). However, in these cases the primary tricyclic adducts react with a second molecule of ADM to yield corresponding tetracyclic compounds. The new tricyclic aldehydes 16 and 17 which were obtained in up to 50% yield (Scheme 3) could quantitatively be decarbonylated with [RhCl(PPh₃)₃] in toluene at 140° to yield a thermally equilibrated mixture of four tricycles (Scheme 8). It was found that the thermal isomerization of these tricycles occur at temperatures as low as 0° and that at temperatures > 40° the thermal equilibrium between the four tricycles is rapidly established via [1,5]-C shifts. The establishment of the equilibrium makes the existence of two further tricycles necessary (cf. Scheme 8). However, in the temperature range of up to 85° these two further tricycles could not be detected by ¹H-NMR. When heated in the presence of excess ADM in decalin at 180°, the ‘missing’ tricyclic forms could be evidenced by their tetracyclic trapping products ‘anti’- 45 and ‘anti’- 48 , respectively (Scheme 9).     

Heterocyclic systems. VIII. synthesis of 1H,4H-pyrazolo[4,3-f]pyrrolo[1,2-a]azepine derivatives

The synthesis of the unknown title Compounds is described. The preparation involves intramolecular acylation of 3-[1-phenyl-5-(1-pyrryl)pyrazol-4-yl]propanoic acid 9 to the tricyclic ketone 10 , which was then transformed into 1H,4H-pyrazolo[4,3-f]pyrrolo[1,2-a]azepine 12 and its dihydro derivative 13 by reductive procedures.     

Metallderivate von Molekülverbindungen. III. Molekül- und Kristallstruktur des Lithium-bis (trimethylsilyl)-phosphids · DME und des Lithium-dihydrogenphosphids · DME

Metal Derivatives of Molecular Compounds. III. Molecular and Crystal Structure of Lithium bis(trimethylsilyl)phosphide · DME and of Lithium dihydrogenphosphide · DME Lithium bis(trimethylsilyl)phosphide · DME 1 prepared from tris(trimethylsilyl)-phosphine and lithium methanide [2, 4] in 1,2-dimethoxyethane

1 1,2-Dimethoxyethan (DME); Tetrahydrofuran (THF); Bis[2-(dimethylamino)ethyl]methyl-amin (PMDETA).

, crystallizes in the orthorhombic space group Pnnn {a = 881.1(9); b = 1308.5(9); c = 1563.4(9) pm at ?120 ± 3°C; Z = 4 formula units}, lithium dihydrogenphosphide · DME 2 [10] prepared from phosphine and lithium- n -butanide in the same solvent, in P2 ₁ 2 ₁ 2 ₁ {a = 671.8(1); b = 878.6(1); c = 1332.2(2) pm at ?120 ± 3°C; Z = 4 formula units}. X-ray structure determinations (R _w = 0.036/0.045) show the bis(trimethylsilyl) derivative 1 to be dimeric with a planar P? Li? P? Li ring (P? Li 256 pm; Li? P? Li 76°; P? Li? P 104°), and the dihydrogenphosphide 2 to be polymeric with a linear Li? P? Li fragment (P? Li 254 to 260 pm; Li? P? Li 177°; P? Li? P 118°). The shortened P? Si distance (221 pm) of compound 1 and the structure of the PH ₂ group in 2 are discussed in detail. Lithium obtains its preferred coordination number 4 by a chelation with one molecule of 1,2-dimethoxyethane (Li? O 202 to 204 pm).     

Metallderivate von Molekülverbindungen. IV. Synthese,Struktur und Reaktivität des Lithium-[tris-(trimethylsilyl)silyl]tellanids · DME

Metal Derivatives of Molecular Compounds. IV Synthesis, Structure, and Reactivity of Lithium [Tris(trimethylsilyl)silyl]tellanide · DME Lithium tris(trimethylsilyl)silanide · 1,5 DME [3] and tellurium react in 1,2-dimethoxyethane to give colourless lithium [tris(trimethylsilyl)silyl]tellanide · DME ( 1 ). An X-ray structure determination {-150 · 3·C; P2₁/c; a = 1346.6(4); b = 1497.0(4); c = 1274.5(3) pm; β = 99.22(2)·; Z = 2 dimers; R = 0.030} shows the compound to be dimeric forming a planar Li? Te? Li? Te ring with two tris(trimethylsilyl)silyl substituents in a trans position. Three-coordinate tellurium is bound to the central silicon of the tris(trimethylsilyl)silyl group and to two lithium atoms; the two remaining sites of each four-coordinate lithium are occupied by the chelate ligand DME {Li? Te 278 and 284; Si? Te 250; Li? O 200 pm (2X); Te? Li? Te 105°; Li? Te? Li 75°; O? Li? O 84°}. The covalent radius of 154 pm as determined for the DME-complexed lithium in tellanide 1 is within the range of 155 ± 3 pm, also characteristic for similar compounds. In typical reactions of the tellanide 1 [tris(trimethylsilyl)silyl]tellane ( 2 ), methyl-[tris(trimethylsilyl)silyl]tellane ( 4 ) and bis[tris(trimethylsilyl)silyl]ditellane ( 5 ) are formed.