π-cyclohexadienyliron complexes bearing exocyclic double bonds

Sodium amide and sodium bis(trimethylsilyl)amide abstract α protons from certain π-arene-π-cyclopentadienylixon(II) cations to produce neutral π-cyclohexadienyl complexes bearing exocyclic CC or CN bonds. Also reported are the first examples of π-arene-π-cyclopentadienyliron(II) cations of aromatic amines synthesized by direct reaction of the amine, ferrocene and AlCl₃.     

One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O

A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr₂·2Et₂O as catalyst.     

N-substituted hexamethyldisilazanes as new substances for the synthesis of functional films in the system Si-Ge-C-N-H

N-Organylbis(trimethylsilyl)amines of the general formula RN(SiMe₃)₂ (R = Me₃Si, Et₃Ge) were synthesized by reaction of sodium bis(trimethylsilyl)amide with the corresponding trialkylsilyl(germyl) halide. Their IR, UV, and ¹H, ¹³C, and ²⁹Si NMR spectra were studied, and saturated vapor pressures and thermal stabilities were determined. The possibility of using the RN(SiMe₃)₂ compounds as precursors in chemical vapor deposition of films with specified composition was estimated by thermodynamic modeling.     

Lewis acid-controlled reactions of zirconacyclopentadienes with isocyanates and isothiocyanates. One-pot three- or four-component synthesis of multiply substituted iminocyclopentadienes and butadiene-tethered 1,6-bisamides and electrophilic cyclization

Multiply substituted zirconacyclopentadienes including bicyclic zirconacyclopentadienes and zirconaindenes reacted with isocyanates and isothiocyanates in the presence of Lewis acids to afford iminocyclopentadienes and conjugated 1,6-bisamides, depending on the nature of Lewis acids, isocyanates, and isothiocyanates used. Only in the presence of BF₃ could iminocyclopentadienes be obtained in high isolated yields when zirconacyclopentadienes were treated with isocyanates. On the contrary, BF₃ could not mediate the reaction of zirconacyclopentadienes with isothiocyanates. For the reactions of zirconacyclopentadienes with isothiocyanates, EtAlCl₂ was found effective to generate iminocyclopentadienes as the products. Interestingly, however, for the reactions of zirconacyclopentadienes with isocyanates, EtAlCl₂ was found to work very differently from BF₃. Instead of iminocyclopentadienes, conjugated 1,6-bisamides and conjugated mono-amides were obtained as products in high isolated yields from the reactions of zirconacyclopentadienes with isocyanates, depending on the substituents of isocyanates. The reaction path and products could be controlled by Lewis acids. As a demonstration of the usefulness of thus obtained unsaturated bisamides, electrophilic cyclization using acids, NBS, and I₂ was carried out. Electrophilic cyclization of multisubstituted conjugated 1,6-bisamide derivatives afforded cyclic iminoethers in excellent yields with perfect selectivity. Only one of the amide groups took part in the electrophilic cyclization.     

One‐Pot Three‐Component Synthesis of α‐Amino Nitriles Catalyzed by 2,4,6‐Trichloro‐1,3,5‐triazine (Cyanuric Acid)

A simple and efficient method has been developed for the synthesis of α‐amino nitriles from aldehydes, amines and trimethylsilyl cyanide (Me₃SiCN) in the presence of a catalytic amount of cyanuric acid at room temperature.     

Diastereoselective synthesis of multisubstituted isoindolines via Sequential Ugi and aza-Michael addition reaction

A new efficient and diastereoselective synthesis of multisubstituted isoindolines with two stereogenic centers via sequential Ugi/aza-Michael addition reaction was developed. Ugi-3CR of aldehydes 1, amines 2 and isocyanates 3 in the presence of catalytic amount of H₃PO₄ produced intermediates 4, which were then transformed to isoindolines 5 with good 1,3-trans diastereoselectivity in the presence of K₂CO₃ by intramolecular aza-Michael addition. Sequential Ugi-azide and aza-Michael addition reaction of aldehydes 1, amines 2 and trimethylsilyl azide 6 also produced 4-tetrazolyl substituted isoindolines 8 with good 1,3-trans diastereoselectivity in the presence of potassium carbonate.     

Synthesis of Guanidines from Amines and Carbodiimides Catalyzed by Mono‐Indenyl‐Ligated Rare Earth Metal Bis(silylamide) Complexes

Nucleophilic addition of primary aromatic amines to carbodiimides in the presence of catalytic amount of the mono‐indenyl‐ligated rare earth metal bis(silylamide) complexes (C₉H₆CMe₂CH₂C₅H₄N‐α)Ln[N(SiHMe₂)₂]₂ at room temperature afforded efficiently a series of guanidines with a wide spectrum of substituents on the nitrogen atoms.     

Bis(trimethylsilyl)amide und -methanide des Yttriums — Molekülstrukturen von Tris(diethylether-O)lithium-(μ-chloro)-tris[bis(trimethylsilyl) methyl]yttriat,solvensfreiem Yttrium-tris[bis(trimethylsilyl)amid] sowie dem Bis(benzonitril)-Komplex

Bis(trimethylsilyl)amides and -methanides of Yttrium — Molecular Structures of Tris(diethylether-O)lithium-(μ-chloro)-tris[bis(trimethylsilyl)methyl]yttriate, solvent-free Yttrium Tris[bis(trimethylsilyl)amide] as well as the Bis(benzonitrile) Complex The reaction of yttrium(III) chloride with the three-fold molar amount of LiE(SiMe₃)₂ (E = N, CH) yields the corresponding yttrium derivatives. Yttrium tris-[bis(trimethylsilyl)amide] crystallizes in the space group P3 1c with a = 1 636,3(2), c = 849,3(2) pm, Z = 2. The yttrium atom is surrounded trigonal pyramidal by three nitrogen atoms with Y? N-bond lengths of 222 pm. Benzene molecules are incorporated parallel to the c-axes. The compound with E = CH crystallizes as a (Et₂O)₃LiCl-adduct in the monoclinic space group P2₁/n with a = 1 111,8(2), b = 1 865,2(6), c = 2 598,3(9) pm, β = 97,41(3)° and Z = 4. The reaction of yttrium tris[bis(trimethylsilyl)amide] with benzonitrile yields the bis(benzonitrile) complex, which crystallizes in the triclinic space group P1 with a = 1 173,7(2), b = 1 210,3(2), c = 1 912,4(3) pm, α = 94,37(1), β = 103,39(1), γ = 117,24(1)° and Z = 2. The amido ligands are in equatorial, the benzonitrile molecules in axial positions.     

Niobium(V) chloride‐catalyzed synthesis of α‐aminonitriles with simultaneous reaction of aldehydes,amines and trimethylsilyl cyanide

A simple and efficient one‐pot method has been developed for the synthesis of α‐aminonitriles by concurrent reaction of aldehydes, amines and trimethylsilyl cyanide with a catalytic amount of NbCl₅ (10 mol%) in CH₃CN at room temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

A traceless approach for the solid-phase synthesis of 6-amino-1,3,5-triazine-2,4-diones

A traceless approach for the solid-phase synthesis of 6-amino-1,3,5-triazine-2,4-diones is described. Reaction of resin-bound S-methylisothiourea with isocyanates yielded resin-bound iminoureas 3, which reacted with amines to afford the corresponding guanidines 4. Following intramolecular cyclizative cleavage of the resin-bound guanidines using potassium ethoxide as a base, the desired products 5 were obtained in good yields and high purities.     

Efficient Iminophosphorane‐Mediated Preparation of Benzofuro[3,2‐d]pyrimidin‐4(3H)‐ones and Unexpected Ring Opening Products

The carbodiimides 4 , obtained from aza‐Wittig reactions of iminophosphorane 3 with aromatic isocyanates, reacted with secondary amines, phenols or alcohols in the presence of catalytic amounts of K₂CO₃ or sodium alkoxide to give 2‐substituted benzofuro[3,2‐d]pyrimidin‐4(3H)‐ones 6 . However, when 2,2′‐iminobis[ethanol] was used, the unexpected ring opening product 7 was formed instead of 6 . Reaction of 4 with primary amines RNH₂ (R=Et, Pr, Bu, etc.) gave guanidine intermediates 8 , which were further treated with EtONa to give only one regioisomer 9 via a base catalyzed cyclization. However, another regioisomer 11 was obtained when NH₃ or ‘small’ amines RNH₂ (R=Me, NH₂) were used in the absence of EtONa via a spontaneous cyclization of 8 .     

Speciation of Aluminium in Mixtures of the Ionic Liquids [C3mpip][NTf2] and [C4mpyr][NTf2] with AlCl3: An Electrochemical and NMR Spectroscopy Study

This paper reports on the electrodeposition of aluminium on several substrates from the air‐ and water‐stable ionic liquids 1‐propyl‐1‐methylpiperidinium bis(trifluoromethylsulfonyl)amide ([C₃mpip][NTf₂]) and 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C₄mpyr][NTf₂]), which contain anhydrous AlCl₃. At an AlCl₃ concentration of 0.75 molal, no evidence for aluminium electrodeposition was observed in either system at room temperature. However, aluminium electrodeposition becomes feasible upon heating the samples to 80 °C. Aluminium electrodeposition from bis(trifluoromethylsulfonyl)amide‐based ionic liquids that contain AlCl₃ has previously been shown to be very dependent upon the AlCl₃ concentration and has not been demonstrated at AlCl₃ concentrations below 1.13 molal. The dissolution of AlCl₃ in [C₃mpip][NTf₂] and [C₄mpyr][NTf₂] was studied by variable‐temperature ²⁷Al NMR spectroscopy to gain insights on the electroactive species responsible for aluminium electrodeposition. A similar change in the aluminium speciation with temperature was observed in both ionic liquids, thereby indicating that the chemistry was similar in both. The electrodeposition of aluminium was shown to coincide with the formation of an asymmetric four‐coordinate aluminium‐containing species with an ²⁷Al chemical shift of δ=94 and 92 ppm in the [C₃mpip][NTf₂]–AlCl₃ and [C₄mpyr][NTf₂]–AlCl₃ systems, respectively. It was concluded that the aluminium‐containing species that give rise to these resonances corresponds to the electroactive species and was assigned to [AlCl₃(NTf₂)]^?.     

Enantioselective synthesis of butadien-2-ylcarbinols via (silylmethyl)allenic alcohols from chromium-catalyzed additions to aldehydes utilizing chiral carbazole ligands

The synthesis of chiral, nonracemic butadienylcarbinols by employing intermediate (trimethylsilyl)methylallenic alcohols is described. Allenic alcohols are obtained by treatment of aldehydes with (4-bromobut-2-ynyl)trimethylsilane in the presence of a catalytic amount of CrCl₃ or CrCl₂. Several new tridentate bis(oxazolinyl)carbazole ligands were synthesized and evaluated as the source of chirality. The synthesis of chiral allenic alcohols can be achieved in good yields (58-88%) and enantioselectivities (55-78% ee). Allenic alcohols may be treated with TBAF or 2 M HCl to provide the desired dienes in 43-86% yields. Alternatively, the (trimethylsilyl)methyl allenic alcohols afford iodobutadienyl carbinols when treated with N-iodosuccinimide.     

Reaction of sodium bis(trimethylsilyl)amide with 2-bromopyridine

A reaction of sodium bis(trimethylsilyl)amide with 2-bromopyridine leads to N,N-bis(trimethylsilyl)- and N,3-bis(trimethylsilyl)-2-pyridinamine.     

An Efficient Synthesis of 3H‐Pyrrolo[3,2‐d]pyrimidin‐4(5H)‐one Derivatives via an Iminophosphorane

The iminophosphorane ( 3 ), obtained from reaction of ethyl 3‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrrole‐2‐carboxylate ( 2 ) with triphenylphosphine, hexachloroethane, and triethylamine, reacted with aromatic isocyanates to give carbodiimides ( 4 ). Further reaction of 4 with various amines, phenols, or ROH to give 2,3,5,7‐tetrasubstituted 3H‐pyrrolo[3,2‐d]pyrimidine‐4(5H)‐ones ( 6 ) in satisfactory yields in the presence of catalytic amount of sodium alkoxide or solid potassium carbonate.     

Syntheses,Crystal Structure and Reactivity of Tin(II) Bis[N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide]

Metallation of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine with n‐butyllithium in toluene yields lithium N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide ( 1 ), which crystallizes as a tetramer. Transamination of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine with an equimolar amount of Sn[N(SiMe₃)₂]₂ leads to the formation of monomeric bis(trimethylsilyl)amido tin(II) N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide ( 2 ). The addition of another equivalent of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine gives homoleptic tin(II) bis[N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide] ( 3 ). In these complexes the N‐(diphenylphosphanyl)(2‐pyridylmethyl)amido groups act as bidentate bases through the nitrogen bases. At elevated temperatures HN(SiMe₃)₂ is liberated from bis(trimethylsilyl)amido tin(II) N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide ( 2 ) yielding mononuclear tin(II) 1,2‐dipyridyl‐1,2‐bis(diphenylphosphanylamido)ethane ( 4 ) through a C–C coupling reaction. The three‐coordinate tin(II) atoms of 2 and 4 adopt trigonal pyramidal coordination spheres.     

Lewis Acid Promoted Reactions. (IV.)1a,b Oxidation Deprotection of Trimethylsilyl Ethers with Silver and Sodium Bromates; AgBrO3, NaBrO3

Primary and secondary benzylic and saturated trimethylsilyl ethers are converted to their carbonyl compounds with AgBrO₃/AlCl₃ efficiently. p-Hydroquinonetrimethylsilyl ether is also converted with both AgBrO₃/AlCl₃ and NaBrO₃/AlCl₃ to p-benzoquinone. AgBrO₃/AlCl₃ is also able to oxidize primary trimethylsilyl ethers to their carboxylic acids. Primary and secondary benzylic trimethylsilyl ethers are also converted to their carbonyl compounds with NaBrO₃/AlCl₃; AgBrO₃ is more efficient and selective oxidant than NaBrO₃.     

Bulky Amido Ligands in Rare Earth Chemistry — Syntheses,Structures, and Catalysis

The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe₃)₂}₃], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article.     

Furo- and thieno-fused 1,3-diazepine-4,6-diones

We report the first preparation of furo- and thieno-fused 1,3-diazepine-4,6-dione derivatives starting from ethyl 2-(2-methoxy-2-oxoethyl)-3-furancarboxylate and -thiophencarboxylate. The ester functionalities connected to the hetero-ring were converted regiospecifically into the desired amides. The ester groups attached to the methylene unit were converted into isocyanates via Curtius rearrangement. The ring-closure reaction was performed in the presence of lithium bis(trimethylsilyl)amide at room temperature to give furo- and thieno-fused diazepinone derivatives.     

Efficient synthesis of 2‐substituted thieno[2,3‐d]pyrimidin‐4(3H)‐ones via an iminophosphorane

The carbodiimides 4 , obtained from reactions of iminophosphorane 3 with aromatic isocyanates, were reacted with secondary amines to give 2‐dialkylamino‐5‐ethyl‐6‐methyl‐thieno[2,3‐d]pyrimidin‐4(3H)‐ones 6 in the presence of catalytic amount of EtONa. Reactions of 4 with phenols or ROH in the presence of the catalytic amount of K2CO₃ or RONa gave 2‐aryloxy‐ or 2‐alkoxy‐5‐ethyl‐6‐methyl‐thieno[2,3‐d]pyrimidin‐4(3H)‐ones 6 in satisfactory yields. The effects of the nucleophiles on cyclization have been investigated. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:266–270, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20424