Platinum(IV) complexes with α,ω-bis(pyrazol-1-yl) alkanediyl and diethyl ether/thioether ligands. Crystal structures of dibromodimethyl[1,2-bis(pyrazol-1-yl)ethane]platinum(IV) and trimethyl-bis[2-(pyrazol-1-yl)ethyl]etherplatinum(IV) tetrafluoroborate

Reactions of the flexible α,ω-bis(pyrazol-1-yl) compounds 1,2-bis(pyrazol-1-yl)ethane (L1), 1,8-bis(pyrazol-1-yl)-n-octane (L2), bis[2-(pyrazol-1-yl)ethyl]ether (L3) and bis[2-(pyrazol-1-yl)ethyl]thioether (L4) with precursor organometallic platinum complexes ([(PtBr₂Me₂)_n], [(PtIMe₃)₄] and [(PtMe₂(cod)]/I₂) are described herein. The spectroscopic characterization of the platinum(IV) products of these reactions [PtBr₂Me₂{pz(CH₂)_mpz}], m = 2 (1) or 8 (2), [PtI₂Me₂{pz(CH₂)₂pz}] (3), [PtMe₃(pzCH₂CH₂OCH₂CH₂pz)][BF₄] (4) and [PtMe₃(pzCH₂CH₂SCH₂CH₂pz)][CF₃SO₃] (5), where ‘pz’ is pyrazol-1-yl, is discussed. Furthermore, solid state structures of 1, a complex with a seven-membered chelate ring, and 4, a complex bearing the neutral κ²N,N′,κO ligand bis[2-(pyrazol-1-yl)ethyl]ether (L3) are reported.     

Synthesis of cyclolinear permethylpolycarbosilanes with oligosilane fragments in the backbone and study of their properties

Cyclolinear permethylpolycarbosilanes were synthesized for the first time by the reaction of 1,3- and 1,4-dihydrodecamethylcyclohexasilanes H₂Si₆Me₁₀ with α,ω-diallylpermethyloligo-silanes All(SiMe₂) _n All (n = 1–6) in the presence of Karstedt’s catalyst. The molecular weight characteristics, thermal and thermooxidative stability, and the spectral properties of the synthesized polymers were studied. The dependence of the yield and the molecular weight of the synthesized polymers on the number of the SiMe₂ units in the linear oligosilane fragment of the main chain was established.     

Lithium-silylindolide als Precursor für 1,2-, 1,3-Bis(silyl)indole und Bis(indol-1,3-yl)silane

Lithium-silylindolide as Precursor of 1,2-, 1,3-Bis(silyl)indoles and Bis(indole-1,3-yl)silane Lithium-indolide reacts with difluorosilanes (F₂SiR₂: R = CHMe₂ ( 1 ); CMe₃ ( 2 )) in a molar ratio 2 : 1 with formation of bis(indole-1-yl)silanes. The 1-(di-tert-butylfluorosilyl)-3-(fluorodiisopropylsilyl)indole ( 3 ) is obtained in the reaction 1-(di-tert-butylfluorosilyl)-3-lithium-indolide and F₂Si(CHMe₂)₂. In a molar ratio 2 : 1 the bis(1-di-tert-butylfluorosilyl-indole-3-yl)diisopropylsilane 4 is formed. As a byproduct bis(1-di-tert-butylfluorosilyl-indole-3-yl)dimethylmethane ( 5 ) is isolated. A cleavage of THF and the formation of (indole-1-yl)diisopropylvinyloxysilan ( 6 ) occurs in the reaction of 1-diisopropylfluorosilylindole with t-BuLi in THF. 1-(di-tert-butylfluorosilyl)indole reacts with n-BuLi/TMEDA accompanied by an 1,2-anionic silyl group migration to give the 2-(di-tert-butylfluorosilyl)-1-lithiumindolide 7 . Hydrolysis of 7 gives the 2-(di-tert-butylfluorosilyl)indole ( 8 ). In the reaction of 7 with F₂Si(CHMe₂)₂ the 1-(diisopropylfluorosilyl)-2-(di-tert-butylfluorosilyl)indole 9 is obtained. 1-n-Butyl-diisopropylsilylindole ( 10 ) is the product of the reaction of F₂Si(CHMe₂)₂, n-BuLi/TMEDA and indole at –70 °C. Lithium-indolide reacts with 3 to give the 1-(di-tert-butylfluorosilyl)indole-3-yl)(indole-1-yl)-diisopropylsilane ( 11 ), the first example of this class of substances. In the reaction of 1 , F₂SiMe₂, and t-BuLi in THF the 1-(diisopropyl(indole-1-yl)silyl)-3-dimethyl-(3.3-dimethylbutylsilyl)indole 12 is isolated. The crystal structures of 2 , 5 and 9 are discussed.     

Hybrid Calixarene/Inorganic Salt/Diiodoperfluorocarbon Supramolecular Assemblies

1,3-Bis(α-picolyloxy)-p-tert-butylcalix[4]crown-5 in the cone conformation (2), 1,8-diiodoperfluorooctane or 1,6-diiodoperfluorohexane, and potassium iodide ternary mixtures undergo in solution self-sorting and afford crystalline “supramolecular salts”. These hybrid materials consist of supercation [K⁺ ? 2] and superanion [I–(CF₂) _n –I…I^? …I–(CF₂) _n –I…I^? …] (n = 6,8) components. In the supercations the potassium ion is embedded in the ionophoric pocket created by the heteroatoms present at the lower rim. In the superanions the iodide ions form infinite fluorous polyanionic chains as a result of a self-assembly process which relies on halogen bonding. Both cation encapsulation and anion-perfluorocarbon halogen bonding were detected in solution by ¹H and ¹⁹F NMR, and in the gas phase by ESI MS.     

Synthesis of Macrocyclic Lactones via Ring Transformation of 4‐(ω‐Hydroxyalkyl)‐1,3‐oxazol‐5(4H)‐ones

The synthesis of α‐benzamido‐α‐benzyl lactones 23 of various ring size was achieved either via ‘direct amide cyclization’ by treatment of 2‐benzamido‐2‐benzyl‐ω‐hydroxy‐N,N‐dimethylalkanamides 21 in toluene at 90 – 110° with HCl gas or by ‘ring transformation’ of 4‐benzyl‐4‐(ω‐hydroxyalkyl)‐2‐phenyl‐1,3‐oxazol‐5(4H)‐ones under the same conditions. The precursors were obtained by C‐alkylations of 4‐benzyl‐2‐phenyl‐1,3‐oxazol‐5(4H)‐one ( 15 ) with THP‐ or TBDMS‐protected ω‐hydroxyalkyl iodides. Ring opening of the THP‐protected oxazolones by treatment with Me₂NH followed by deprotection of the OH group gave the diamides 21 , whereas deprotection of the TBDMS series of oxazolones 25 with TBAF followed by treatment with HCl gas led to the corresponding lactones 23 in a one‐pot reaction.     

Synthesis of Si-containing cyclic ureas

1,3-Bis[(triethoxysilyl)methyl]tetrahydropyrimidin-2-one and 1,3-bis[(dimethoxysilyl)methyl]tetrahydro-pyrimidin-2-one have been synthesized on interacting urea with N,N′-bis(silylmethyl)propylenamines (EtO)³⁻ⁿMe_nSiCH₂NH(CH₂)₃NHCH₂SiMe_n(OEt)_3−n (n = 0, 2). Their interaction with boron trichloride has been studied. The structures of all the compounds synthesized have been demonstrated by multinuclear NMR spectroscopy. Dedicated to the 50^th Anniversary of the Latvian Institute of Organic Synthesis __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 238–244, February, 2007.     

Ethene homopolymerization and copolymerization with 1‐hexene for all methyl‐substituted (RnC5H5−n)2ZrCL2/MAO catalytic systems: Effects of split methyl substitution

Ethene homopolymerization and copolymerization with 1‐hexene were catalyzed by methyl‐substituted cyclopentadienyl (Cp) zirconium dichlorides, (R_n C₅H_5−n)₂ZrCl₂ (R_n = H, Me, 1,2‐Me₂, 1,3‐Me₂, 1,2,3‐Me₃, 1,2,4‐Me₃, Me₄, or Me₅), and methylaluminoxane. The polymers were characterized with Fourier transform infrared, nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry techniques. Generally, an increasing number of methyl substituents on the Cp ligand results in lower 1‐hexene incorporation in the copolymer. The two catalysts with split methyl substitution (R_n = 1,3‐Me₂ and R_n = 1,2,4‐Me₃) show a higher comonomer response than their disubstituted and trisubstituted counterparts (R_n = 1,2‐Me₂ and R_n = 1,2,3‐Me₃). They even incorporate more 1‐hexene than R_n = H and R_n = Me. These findings are qualitatively in agreement with the results of a theoretical study based on density functional calculations. The presence of comonomer does not influence the termination reactions after the insertion of ethene. There is more frequent termination after each hexene insertion with increasing comonomer incorporation except for the two catalysts with split methyl substituents. The termination probability per inserted comonomer is highest for the less substituted catalysts. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3161–3172, 2000     

Tetraaryl-1,3-dioxolane-4,5-dimethanols as catalysts for the addition of trimethylsilyl cyanide to benzaldehyde and the oxirane ring

The synthesis of 1,2-, 1,3-, and 1,4-phenylene-bis[(4R,5R)-4,5-di(hydroxydiphenylmethyl)-1,3-dioxolane]s (ortho-, meta-, and para-bis-(R,R)-TADDOLs) and bis[4-{[(4R, 5R)-4,5-di(hydroxydiphenylmethyl)]-1,3-dioxolan-2-yl}phenyl]methane was carried out. The possibilities of the use of these compounds as catalysts for the C-C bond formation in the addition of Me₃SiCN to benzaldehyde and the oxirane ring opening in cyclohexene oxide by Me₃SiCN were investigated. The catalytic activity of different bis-(R, R)-TADDOLs in this series depends on their structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1451–1458, August, 2007.     

Preparation and electrochemical behaviour of dinuclear platinum complexes containing NCN ligands (NCN=[C6H3(Me2NCH2)2-2,6]). The crystal structure of [C6H3(Me2NCH2)2-1,3-(CC)-5]2

A series of homodinuclear Pt compounds containing the anionic, potentially terdentate NCN ligand (NCN=[C₆H₃(Me₂NCH₂)₂-2,6]⁻) or its 4-ethynyl derivative were prepared. The two platinum centres are linked together in two different fashions: (i) directly linked by an ethynyl or diethynylphenyl group (head-to-head) and (ii) indirectly bonded by a ethynyl- or butadiynyl-linked bis-NCN ligand (tail-to-tail). The reaction of the head-to-head σ,σ′-ethynylide complex {Pt}CC{Pt} ({Pt}=[Pt(C₆H₃{CH₂NMe₂}₂-2,6)]⁺) with [CuCl]_n yields {Pt}Cl and [Cu₂C₂]_n, while with [Cu(NCMe)₄][BF₄] a Cu(I) bridged complex was formed: [(η²-{Pt}CC{Pt})₂Cu][BF₄]. The results of cyclic voltammetry experiments reveal that both connection modes of the two platinum centres lead to electrochemically independent Pt–NCN units. The X-ray crystal structure analysis of the neutral, tail-to-tail bridging butadiyne bis-NCNH ligand [C₆H₃(CH₂NMe₂)-1,3-(CC)-5]₂ is reported.     

Star poly(methyl methacrylate) with end‐functionalized arm chains by ruthenium‐catalyzed living radical polymerization

Star polymers with end‐functionalized arm chains (surface‐functionalized star polymers) were synthesized by the in situ linking reaction between ethylene glycol dimethacrylate (linking agent) and an α‐end‐functionalized linear living poly(methyl methacrylate) in RuCl₂(PPh₃)₃‐catalyzed living radical polymerization; the terminal on the surface functionalities included amides, alcohols, amines, and esters. The star polymers were obtained in high yields (75–90%) with initiating systems consisting of a functionalized 2‐chloro‐2‐phenylacetate or ‐acetamide [F? C(O)CHPhCl; F = nPrNH? , HOCH₂CH₂O? , Me₂NCH₂CH₂O? , or EtO? ; initiator] and n‐Bu₃N (additive). The yield was lower with a functionalized 2‐bromoisobutyrate [Me₂NCH₂CH₂OC(O)CMe₂Br] initiator or with Al(Oi‐Pr)₃ as an additive. Multi‐angle laser light scattering analysis showed that the star polymers had arm numbers of 10–100, radii of gyration of 6–23 nm, and weight‐average molecular weights of 1.3 × 10⁵ to 3.0 × 10⁶, which could be controlled by the molar ratio of the linking agent to the linear living polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1972–1982, 2002     

Elaboration of rac‐Like Active Species from Lewis Base Functionalized Unbridged Zirconocenes for Isospecific Propylene Polymerization

A series of ortho or meta Lewis base functionalized unbridged zirconocenes, [{1‐(E_n‐Ph)‐3,4‐Me₂C₅H₂}₂ZrCl₂] (E=NMe₂, OMe; n=1, 2), and a half‐functionalized zirconocene, [{1‐(p‐Me₂NC₆H₄)‐3,4‐Me₂C₅H₂}{1‐(p‐tolyl)‐3,4‐Me₂C₅H₂}ZrCl₂], were prepared. The crystal structures of these compounds determined by X‐ray diffraction revealed the presence of only C₂‐symmetric rac‐like isomers in the asymmetric units. In combination with methylaluminoxane (MAO) cocatalyst, the meta‐functionalized complexes afforded mixtures of polymers that exhibit multimelting transition temperatures and broad molecular‐weight distributions (MWDs) in propylene polymerization at atmospheric monomer pressure, whereas the ortho‐functionalized complexes did not give rise to polymerization. Stepwise solvent extraction of the polymer mixtures showed that the polymers consist of amorphous, moderately isotactic, and highly isotactic portions, the weight ratio of which is dependent on the reaction temperature. ¹³C NMR spectral analysis indicated that the [mmmm] methyl pentad value of the isotactic portion reached around 90 %. Among the meta‐functionalized zirconocenes, the di‐OMe‐substituted one afforded the largest amount of the isotactic portion at all temperatures, and the portion comprised 82 wt % of the crude polymer obtained at 25 °C. In contrast, propylene polymerization with the half‐functionalized unbridged zirconocene resulted in the formation of nearly atactic polypropylene with a narrow MWD of around 2. These results corroborate the proposition that the rigid rac‐like cation–anion ion pair of type [rac‐L₂ZrP]⁺[Me‐MAO]^? generated in situ, through Lewis acid–base interactions between the functional groups and [Me‐MAO]^?, is responsible for the isospecific propylene polymerization with the given class of functionalized unbridged zirconocenes and further indicate that the formation of such ion pairs can be favored by difunctionalization at the meta position of the phenyl ring with OMe groups.     

Cationic ring-opening polymerizations of cyclic ketene acetals initiated by acids at high temperatures

Three unsubstituted cyclic ketene acetals (CKAs), 2-methylene-1,3-dioxolane, 1a , 2-methylene-1,3-dioxane, 2a , and 2-methylene-1,3-dioxepane, 3a , undergo exclusive 1,2-addition polymerization at low temperatures, and only poly(CKAs) are obtained. At higher temperatures, ring-opening polymerization (ROP) can be dominant, and polymers with a mixture of ester units and cyclic ketal units are obtained. When the temperature is raised closer to the ceiling temperature (T_c) of the 1,2-addition propagation reaction, 1,2-addition polymerization becomes reversible and ring-opened units are introduced to the polymer. The ceiling temperature of 1,2-addition polymerization varies with the ring size of the CKAs (lowest for 3a , highest for 2a ). At temperatures below 138°C, 2-methylene-1,3-dioxane, 2a , underwent 1,2-addition polymerization. Insoluble poly(2-methylene-1,3-dioxane) 100% 1,2-addition was obtained. At above 150°C, a soluble polymer was obtained containing a mixture of ring-opened ester units and 1,2-addition cyclic ketal units. 2-Methylene-1,3-dioxolane, 1a , polymerized only by the 1,2-addition route at temperatures below 30°C. At 67–80°C, an insoluble polymer was obtained, which contained mostly 1,2-addition units but small amounts of ester units were detected. At 133°C, a soluble polymer was obtained containing a substantial fraction of ring-opened ester units together with 1,2-addition cyclic ketal units. 2-Methylene-1,3-dioxepane, 3a , underwent partial ROP even at 20°C to give a soluble polymer containing ring-opened ester units and 1,2-addition cyclic ketal units. At −20°C, 3a gave an insoluble polymer with 1,2-addition units exclusively. Several catalysts were able to initiate the ROP of 1a, 2a , and 3a , including RuCl₂(PPh₃)₃, BF₃, TiCl₄, H₂SO₄, H₂SO₄ supported on carbon, (CH₃)₂CHCOOH, and CH₃COOH. The initiation by Lewis acids or protonic acids probably occurs through an initial protonation. The propagation step of the ROP proceeds via an S_N2 mechanism. The chain transfer and termination rates become faster at high temperatures, and this may be the primary reason for the low molecular weights (M_n ≤ 10³) observed for all ring-opening polymers. The effects of temperature, monomer and initiator concentration, water content, and polymerization time on the polymer structure have been investigated during the Ru(PPh₃)₃Cl₂-initiated polymerization of 2a . High monomer concentrations ([M]/[ln]) increase the molecular weight and decreased the amount of ring-opening. Higher initiator concentrations (Ru(PPh₃)₃Cl₂) and longer reaction times increase molecular weight in high temperature reactions. Successful copolymerization of 2a with hexamethylcyclotrisiloxane was initiated by BF₃OEt₂. The copolymer obtained displayed a broad molecular weight distribution; M̄_n = 6,490, M̄_w = 15,100, M̄_z = 44,900. This polymer had about 47 mol % of ( Me₂SiO ) units, 35 mol % of ring-opened units, and 18 mol % 1,2-addition units of 2a . © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3655–3671, 1997     

Synthesis of new cyclolinear permethyloligosilane-siloxanes

α,ω-Bis(heptamethylcyclotetrasiloxanyloxy)oligodimethylsilanes were synthesized for the first time by heterofunctional condensation of hydroxyheptamethylcyclotetrasiloxane with α,ω-dichloropermethyloligosilanes, Cl(Me₂Si) _n Cl (n=2, 4, or 6). The compounds obtained were characterized by spectroscopic methods. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 544–545, March, 1998.     

Novel initiators for oxazoline polymerization: generation of polydiacetylene-polyoxazoline networks

A series of bolaform polyoxazolines (POZO) with 1,3-diacetylene cores ((POZO)_m-(CH₂)_n-C≡C-C≡C-(CH₂)_n-(POZO)_m) were synthesized by the living polymerization of 2-methyl-1,3-oxazolines initiated by triflate esters derived from bis(ω-hydroxyalkyl)-1,3-diacetylenes. The chain length of the alkylspacers within the diacetylene core as well as the length of the attached polyoxazoline chains was varied between n = 1 and 4; m = 5, 10 and 15. The thermally induced 1,4-addition process yielding polydiacetylenes (PDA) was studied leading to highly conjugated POZO-PDA hybrid materials.     

Mechanistic and Synthetic Studies on the Formation of 1,2,4-Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

The photooxygenation of (4R,4aS,7R)-4,4a,5,6,7,8-hexahydro-4,7-dimethyl-3H-2-benzopyran ( 16 ) was performed in (i) MeOH, (ii) acetaldehyde, and (iii) acetone at ?78°. The products obtained respectively were (i) (2R)-2-[(1S,4R)-4-methyl-2-oxocyclohexyl]propyl formate ( 17 ; 72% yield), (ii) 17 (54.5%), (1R,4R,4aS,7R)-3,4,4a,5,6,7-hexahydro-4,7-dimethyl-1H-2-benzopyran-2-yl hydroperoxide ( 19 ; 16.7%), a 12:1 ratio of (3R,4aR,7R,7aS,10R,11aR)-7,7a,8,9,10,11-hexahydro-3,7,10-trimethyl-6H-[2]benzopyrano[1,8a-e]-1,2,4-trioxane ( 20 ) and its C(3)-epimer 21 (17%), together with evidence for the 1,2-dioxetane ( 22 ) originating from the addition of dioxygen to the re-re face of the double bond of 16 , and iii) unidentified products and traces of 22 . Addition of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) to the acetone solution of 16 after photooxygenation afforded (4aR,7R,7aS,10R,11aR)-7,7a,8,9,10,11-hexahydro-3,3,7,10-tetramethyl-6H-[2]benzopyrano[1,8a-e]-1,2,4,-trioxane ( 23 , 40%). The photooxygenation of 16 in CH₂Cl₂ at ?78° followed by addition of acetone and Me₃SiOTf afforded 17 (11%), 23 (59%), and (4aR,7R,7aS,10R,11aR)-7,7a,8,9,10,11-hexahydro-3,3,7,10-tetramethyl-6H-[2]benzopyrano[8a,1-e]-1,2,4-trioxane ( 24 ; 5%. Repetition of the last experiment, but replacing acetone by cyclopentanone, gave 17 (16%), (4′aR,7′R,7′aS,10′R,11′aR)-7′,7′a,8′,9′,10′,11′-hexahydro-7′,10′-dimethylspiro[cyclopentane-1,3′-6′H-[2]benzopyrano[1,8a-e]-1,2,4-trixane] ( 25 ; 61%), and (4′aR,7′R,7′aS,10′R,11′aR)-7′,7′a,8′,9′,10′,11′-hexahydro-7′,10′-dimethylspiro[cyclopentane-1,3′-6′H-[2]benzopyrano[8a,1-e]-1,2,4-trixane] ( 26 , 4%). The X-ray analysis of 23 was performed, which together with the NMR data, established the structure of the trioxanes 20, 21, 24, 25 , and 26 . Mechanistic and synthesis aspects of these reactions were discussed in relation to the construction of the 1,2,4-trioxane ring in arteannuin and similar molecules.     

1.3-DITHIOL-2-THION-4.5-DITHIOLAT AUS SCHWEFELKOHLENSTOFF UND ALKALIMETALL

Abstract

Die Reaktion von Schwefelkohlenstoff mit Natrium oder Kalium führt zur Bildung äquimolarer Mengen von 1.3-Dithiol-2-thion-4.5-dithiolat (1) und Trithiocarbonat. Durch Zugabe von ZnCl₂ und NEt₄Br läßt sich (1) stabilisieren. Der entstehende Zink-Komplex ermöglicht die Herstellung von 4.5-Bis(benzoylthio)-1.3-dithiol-2-thion (10), woraus durch Umsetzung mit Basen (1) in quantitativer Ausbeute wieder entsteht. Die Alkylierung von (1) führt zu 4.5-Bis(alkylthio)-1.3-dithiol-2-thionen. (1) is ein neuer, schwefelreicher 1.2-Dithiolat-Ligand. Die Kristallstruktur des Bis-Chelates von (1) mit Ni(II) als (n-Bu₄N)₂-Salz bestätigt die für (1) angenommene Struktur.

The reaction of carbon disulfide with sodium or potassium in dimethyl formamide yields 1,3-dithiole-2-thione-4,5-dithiolate (1) and trithiocarbonate in equimolar amounts. (1) was stabilized by addition of ZnCl₂ and NEt₄Br. The resulting zinc complex enables the isolation of 4,5-bis(benzoylthio)-1,3-dithiole-2-thione (10). (1) can be recovered from (10) by bases with quantitative yield. (1) represents a new multi-sulfur 1,2-dithiolate ligand. The crystal and molecular structure of the bis-complex of (1) with Ni(II) ((n-Bu₄N)₂-salt) confirms the structure of (1).     

Use of Neodymium Diiodide in the Synthesis of Organosilicon, ‐Germanium and ‐Tin Compounds

The reactivity of neodymium diiodide, NdI₂ ( 1 ), towards organosilicon, ‐germanium and ‐tin halides has been investigated. Compound 1 readily reacts with Me₃SiCl in DME to give trimethylsilane (6 %), hexamethyldisilane (4 %) and (Me₃Si)₂O (19 %). The reaction with Et₃SiBr in THF results in formation of Et₃SiSiEt₃ (17 %) and Et₃SiOBuⁿ (34 %). Alkylation of Me₃SiCl with PrⁿCl in the presence of 1 in THF affords Me₃SiPrⁿ (10 %), Me₃SiOBuⁿ (52 %) and Me₃SiSiMe₃ (1 %). The main product identified in the reaction mixture formed upon interaction of 1 with dichlorodimethylsilane Me₂SiCl₂ in THF is di‐n‐butoxydimethylsilane Me₂Si(OBuⁿ)₂ (54 %) together with minor amounts of Me₂Si(OBuⁿ)Cl. The reaction of 1 with Me₃GeBr under the same conditions produces Me₃GeGeMe₃ (44 %), Me₃GeH (3 %), and Me₃GeI (7 %). An analogous set of products was obtained in the reaction with Et₃GeBr. Treatment of trimethyltin chloride with 1 causes reduction of the former to tin metal (74 %). Me₃SnH (7 %) and hexamethyldistannane (11 %) were identified in the volatile products. The reaction of 1 with Me₃SiI provides straightforward access to hepta‐coordinated NdI₃(THF)₄ ( 2 ), the structure of which was determined by X‐ray diffraction.     

Poly-Diels-Alder Addition with a Bisoxazole as Bisdiene and a Bismaleinimide as Bisdienophile

Abstract

The poly-Diels-Alder addition between the new bisdiene 1,4-bis(5-methoxy-2-oxazolyl)benzene (4) and N,N′-hexamethylene-bis[2-(2,5-dihydro-2,5-dioxo-pyrrole-1-yl) acetamide] (7) is described. The structure of the resulting polyadduct 12 was proved by ¹H NMR spectroscopy with the aid of the low-molecular-weight model compounds 1,4-bis(1,3-dihydro-7-hydroxy-1,3-dioxo-2-phenyl-pyrrolo[3,4-c] pyridine-4-yl)benzene (9) and N,N'-hexamethylene-bis[2-(1, 3-dihydro-7-hydroxy-6-methyl-1,3-dioxo-4-phenyl-pyrrolo [3,4-c]pyridine-2-yl)acetamide] (11). The reaction proceeds via the aromatization of the primarily formed cycloadducts. Polyadduct 12 shows a number average degree of polymerization P_n of about 11 – 12 (M_n = 8500 ? 9200 g/mol), calculated from ¹H NMR endgroup signals.     

Fullerene-Acetylene Molecular Scaffolding: Chemistry of 2-functionalized 1-ethynylated C60, oxidative homocoupling,hexakis-adduct formation,and attempted synthesis of C

On the way to the fullerene-acetylene hybrid carbon allotropes 2 and 6 , the oxidative homocoupling of the 2-functionalized 1-ethynylated C₆₀ derivatives 11, 12, 14 , and 15 was investigated. Under Glaser-Hay conditions, the two soluble dumbbell-shaped bisfullerenes 17 and 18 , with two C₆₀ moieties linked by a buta-1,3-diynediyl bridge, were formed in 52 and 82% yield, respectively (Scheme 2). Cyclic-voltammetric measurements revealed that there is no significant electronic communication between the two fullerene spheres via the buta-1,3-diynediyl linker. Removal of the 3,4,5,6-tetrahydro-2H-pyran-2-yl (Thp) protecting groups in 18 gave in 80% yield the highly insoluble dumbbell 19 with methanol groups in the 2,2′-positions of the buta-1,3-diynediyl-bridged carbon spheres. Attempted conversion of 19 to the all-carbon dianion 6 (C) via base-induced elimination of formaldehyde was not successful presumably due to exo-dig cyclization of the formed alkoxides. The occurrence of this cyclization under furan formation was proven for 2-[4-(trimethylsilyl)buta-1,3-diyn-1-yl][60]fullerene-1-methanol ( 21 ), a soluble model compound for 19 (Scheme 3). To compare the properties of ethynylated fullerene mono-adducts to those of corresponding higher adducts, hexakis-adducts 26 and 28 with an octahedral functionalization pattern resulting from all-e (equatorial) additions were prepared by the reversible-template method of Hirsch (Scheme 4). Reaction of the ethynylated mono-adducts 25 or 13 with diethyl 2-bromomalonate/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in the presence of 1,9-dimethylanthracene (DMA) as reversible template led to 26 and 28 in 28 and 22% yield, respectively. Preliminary experiments indicated a significant change in reactivity and NMR spectral properties of the fullerene addends with increasing degree of functionalization.     

2,2‐Difluor‐1,3‐diaza‐2‐sila‐cyclopenten – Synthese und Reaktionen

2,2‐Difluor‐1,3‐diaza‐2‐sila‐cyclopentene – Synthesis and Reactions N,N′‐Di‐tert‐butyl‐1,4‐diaza‐1,3‐butadiene reacts with elemental lithium under reduction to give a dilithium salt, which forms with fluorosilanes the diazasilacyclopentenes 1 – 4 ; (HCNCMe₃)₂SiFR, R = F ( 1 ), Me ( 2 ), Me₃C ( 3 ), N(CMe₃)SiMe₃ ( 4 ). As by‐product in the synthesis of 1 , the tert‐butyl‐amino‐methylene‐tert‐butyliminomethine substituted compound 5 was isolated, R = N(CMe₃)‐CH₂‐CH = NCMe₃. 5 is formed in the reaction of 1 with the monolithium salt of the 1,4‐diaza‐1,3‐butadiene in an enamine‐imine‐tautomerism. 1 reacts with lithium amides to give (HCNCMe₃)₂SiFNHR, 6 – 12 , R = H ( 6 ), Me ( 7 ), Me₂CH ( 8 ), Me₃C ( 9 ), H₅C₆ ( 10 ), 2,6‐Me₂C₆H₃ ( 11 ), 2,6‐(Me₂CH)₂C₆H₃ ( 12 ). The reaction of 12 with LiNH‐2.6‐(Me₂CH)₂C₆H₃ leads to the formation of (HCNCMe₃)₂Si(NHR)₂, ( 13 ). In the presence of n‐BuLi, 12 forms a lithium salt which looses LiF in boiling toluene. Lithiated 12 adds this LiF and generates a spirocyclic tetramer with a central eight‐membered LiF‐ring ( 14 ), [(HCNCMe₃)₂Si(FLiFLiNR)]₄, R = 2,6‐(Me₂CH)₂C₆H₃. ClSiMe₃ reacts with lithiated 12 to yield the substitution product (HCNCMe₃)₂SiFN(SiMe₃) R, ( 15 ). The crystal structures of 1 , 5 , 6 , 9 , 11 , 13 , 14 are reported.