Réactions d'addition-élimination à partir d'hétérocycles germaniés du type R2Ge. II. Les germa-2-diazolidines-1,3

Addition-elimination reactions from germanium heterocycles . II. 2-Germa-1,3-diazolidines (X ? Y ? NMe). The reactivity of 2-Germa-1,3-diazolidines with unsaturated compounds such as heterocumulenes (CS₂, PhNCO, PhNCS) and with carbonyl compounds (aldehydes and ketones) has been investigated. Generally the formation of mono- and diinsertion derivatives is observed. The elimination reactions of (Et₂GeO)_n and (Et₂GeS)₃ from these addition derivatives lead to corresponding carbon diazolidines. The mechanism of these addition-elimination reactions is precised. The interest of these reactions in organic synthesis is underlined.     

Réactions d'addition-élimination à partir d'hétérocycles germaniés du type I. Cas des dioxolannes germaniés

Addition-elimination reactions from germanium heterocycles I. Germadioxolanes (X?Y?O) The reactivity of 2-germa-1,3-dioxolanes is studied with unsaturated compounds such as carbonyl compounds (aldehydes and ketones) or heterocumulenes (PhNCO, PhNCS). The formation of mono- and di-insertion derivatives is observed. The structure of these adducts is established and their decomposition process, at atmospheric pressure or at high pressure, is precised. The mechanism of these addition-elimination reactions is established from 4,5-disubstitued germadioxolanes. The reaction takes place under steric control. The consecutive elimination reaction proceeds by a mechanism of intramolecular nucleophilic substitution.     

Density functional study on the bromination of heteroelement-substituted acetylenes

The reactions of heteroelement-containing alkynes H₃SiC≡CH and R₃MC≡CPh [R₃M = H₃Si, Et₃Si, Et₃Ge, (MeO)₃Si, (EtO)₃Ge, N(CH₂CH₂O)₃Si, N(CH₂CH₂O)₃Ge, Bu₃Sn] with one and two bromine molecules were studied in terms of the density functional theory. Transition states along reaction channels leading to products of both addition at the triple bond (cis- and trans-dibromoalkenes and 1,1-dibromoalkenes) and cleavage of the M-C≡ bond were localized.     

Cycloaddition of germylenes to 3,5-di-t-butyl orthoquinone

The germylenes X₂Ge, RGeX and R₂Ge (X = halogen, OR; R = alkyl or aryl) react at room temperature with 3,5-di-t-butyl orthoquinone by regioselective cycloaddition. The corresponding substituted 2-germa-1,3-dioxolans are formed similarly in good yields, but their stabilities depend on the substituents on the metal. Some of them have also been synthesized by nucleophilic substitution from the corresponding chlorogermanes and 3,5-di-t-butyl catechol. 2-Halo(6,8-di-t-butyl)-4,5-benzo-2-germa-1,3-dioxolans undergo redistribution reactions, while the corresponding dialkyl or diaryl derivatives are very stable.     

Redox reactions of GeII and SnII dihalides with triethylsilane and triethylgermane

Dihalogermylenes, dihalostannylenes, and their complexes (EI₂, ECl₂·dioxane, and (CO)₅W=ECl₂·THF, where E = Ge or Sn), unlike organylgermylenes, are not inserted at the Si—H (Ge—H) bond of triethylsilane (triethylgermane). The reactions of SnI₂, ECl₂·dioxane, and (CO)₅W=ECl₂·THF (E = Ge or Sn) with Et3E"H (E" = Si or Ge) occur as redox processes. Depending on the nature of the reagents, the reactions afford products of oxidative coupling (Et₃SiSiEt₃) and/or haloiodination (Et₃SiX and Et₃GeX) of triethylsilane (triethylgermane). The proposed mechanism of these reactions involves the electron transfer to form radical-ion pairs.     

The reactivity of phosphagermaallene Tip(t-Bu)Ge=C=PMes* with doubly and triply bonded nitrogen compounds

Phosphagermaallene Tip(t-Bu)Ge=C=PMes* (1; Mes* = 2,4,6-tri-tert-butylphenyl, Tip = 2,4,6-triisopropylphenyl) gives, with N-benzylidenemethylamine and pivalonitrile, [2+2] cycloadditions between the Ge=C double bond and the C=N and C≡N unsaturations, leading to the formation of the corresponding four-membered heterocycles 2 and 9. With N-tert-butyl-α-phenylnitrone and benzonitrile oxide, [2+3] cycloadditions occur to form the five-membered ring derivatives 6 and 7. By treatment of 1 with derivatives which possess weak acidic hydrogens in α of the C=N or C≡N multiple bond, two types of reactions were observed: an ene reaction with methyl(benzylideneamino)acetate and a 1,2 addition with acetonitrile to afford azadienyl(germyl)ether (4) and 3-germa-1-phosphapropene (8), respectively. In the case of benzonitrile, phosphagermaallene 1 behaves as a 1,3-dipole, to give, via a cyclic phosphagermacarbene intermediate, the tricyclic derivative 10.     

Molecular geometry and electronic structures of stable organic derivatives of divalent germanium and tin [(\operatorname{Me} _3 \operatorname{Si} )_2 \operatorname{N} {\kern 1pt} ---{\kern 1pt} Me_2 ]_n (M = Ge, n = 1; M = Sn, n = 2): a theoretical study

The molecular geometry and electronic structure of stable organic derivatives of divalent germanium and tin, [(Me₃Si)₂N-M-OCH₂CH₂NMe₂]_n (M = Ge (4), n = 1; M = Sn (5), n =2) and their isomers with broken (4a, 5a) and closed (4b, 5b) intramolecular coordination bonds M←NMe₂, were studied by the density functional (PBE/TZ2P/SBK-JC) and NBO methods. Factors responsible for stability of their dimers 4c and 5c were established. Dimerization of 5b in the gas phase is a thermodynamically favorable process (ΔG ⁰ = ?2.1 kcal mol^?1) while that of 4b is thermally forbidden (ΔG ⁰ = 10.1 kcal mol^?1), which is consistent with experimental data. The M←NMe₂ coordination bond energies, ΔE ⁰, were found to be ?5.3 and ?8.6 kcal mol^?1 for M = Ge and Sn, respectively. NBO analysis showed that the metal atoms M in molecules 4 and 5 are weakly hybridized. The lone electron pairs of the M atoms have strong s-character while vacant orbitals of these atoms, LP* M, are represented exclusively by the metal np_z-AOs. The strongest orbital interactions between subunits in dimers 4c and 5c involve electron density donation from the lone electron pairs of oxygen atoms (LP O) to the LP* M orbitals.     

Fluoridolyse von N-Phosphorylphosphazenen

Fluoridolysis of N-Phosphoryl Phosphazenes In the reaction of the N-phosphoryl phosphazenes X₃P?N? P(Y)X₂ (X = Cl, PhO, Et₂N, CF₃CH₂O, PrS, Ph; Y = O, S) ( 1 – 18 ) with Et₃N · nHF (n ≈? 3 or 0.6) fluoro derivatives of N-phosphoryl phosphazenes (see table 2) as well as N-phosphorylated imiddotetrafluorophosphates, [F₄P?N? P(Y)Cl₂]^? (Y = O, S), and imidopentafluorophosphates, [F₅P? N? P(Y)X₂]^2? or [F₅P? NH? P(O)X₂]^? (see table 3), are formed. t-BuNHPCl₂?N? POCl₂ reacts in acetonitrile with Et₃N or i-Pr₂EtN to form a product, representing probably the diazadiphosphetine ( 5 b ).     

Study of the relative basicity of substituted propynals by IR spectroscopy

Conclusions The donors-acceptor properties of propynals R₃MCCCHO and carbinols R₃MCCCH₂OH (M = C, Ge, Si) in H complexes with phenol and tetrahydrofuran were studied by the IR spectroscopy method. It was found that the R₃MCC fragment in these compounds has an electronacceptor affect. It was shown that the basicity of the aldehydes and the acidity of the corresponding alcohols depend on the nature of the substituents at the triple bond. The electron-donor capacity of the C=O bond of the propynals decreases (the electron-acceptor properties of the OH group of carbinols increase) in the following order:n-Bu-t-Bu > Et₃Ge > Et₃Si > Me₃Si.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1787–1793, August, 1986.     

The kinetics of secondary reactions in the iodination of monogermane. The effect of iodine substitution on the Ge?H bond dissociation energy

A study has been made both of secondary reactions occurring during the reaction of I₂ with GeH₄, and of the direct reaction between I₂ and GeH₃I. Both these studies show that the abstraction reaction occurs about 30 times faster than the reaction in the temperature range of 425–446 K. This information is used to show that iodine substitution weakens Ge–H bonds by 14.4 ± 2.5 kJ/mol and that D(H₂IGe? H) = 332 ± 10 kJ/mol (79.3 kcal/mol). Possible reasons for the effects of halogen substituents on Ge? H and Si? H bond strengths are discussed.     

Tetraphenylantimony <Emphasis Type="Italic">N</Emphasis>-benzoylglycinate: synthesis and structure

Tetraphenylantimony N-benzoylglycinate (I) has been synthesized by the reaction between pentaphenylantimony and N-benzoylglycine in toluene. According to X-ray diffraction data, the antimony atom in a molecule of complex I has a trigonal bipyramidal coordination to the oxygen atom in axial position. The Sb?C_eq, Sb?C_ax, and Sb?O bond lengths are 2.116(6)?2.138(6), 2.183(6), and 2.200(4) Å, respectively. The intramolecular Sb?O=C distance between the carbonyl oxygen atom and the central antimony atom is 3.35(2) Å.     

Di­chloro­maleic anhydride

Although mol­ecules of the title compound, 3,4‐di­chloro‐2,5‐dihydro­furan‐2,5‐dione (di­chloro­maleic anhydride, C₄Cl₂O₃), (I), possess approximate non‐crystallographic C_2v symmetry, the two chlorine substituents deviate from the ring plane. Their deviations are in the same direction, but with values of 0.0356 (17) and 0.0167 (17) Å, they differ significantly in magnitude. The closest intermolecular contact is of 2.888 (2) Å between a carbonyl O atom and the C atom of a carbonyl group, with the O?C direction orthogonal to the C=O bond [O5?C2ⁱ=O2ⁱ 93.6 (2)°; symmetry code: (i) ? x, ?½ + y, z]. These contacts form infinite chains of mol­ecules running parallel to the crystallographic b direction.     

Phénylhalogénohydrodigermanes

The symmetric and unsymmetric phenylchlorohydrodigermanes can be isolated or characterized via partial halogenation of the Ge? H bonds of the symmetrical phenylhydrodigermanes Ph₂(H)GeGe(H)₂Ph, Ph(H)₂GeGe(H)₂Ph by chloromethyl methyl ether and carbontetrachloride. Some of these phenylchlorohydrodigermanes are formed by insertion of phenylchlorogermylene (PhGeCl) on the Ge? H or Ge? Cl bonds of the phenylchlorohydrogermanes. The hydrolysis of the monochloro phenylhydrodigermanes Ph₂(Cl)GeGe(H)₂ and Ph(Cl)(H)GeGe(H)₂Ph leads to the phenyl phenylhydrogermyl digermoxanes [Ph₂(H)GeGePh₂]₂O and [Ph(H)₂GeGe(H)Ph]₂O. Treatment of these oxides with the concentrated aqueous solutions of hydracides leads to the monofluorinated, brominated and iodinated phenylhydrodigermanes Ph₂(H)GeGe(X)Ph₂ and Ph(H)₂GeGe(H)(X)Ph (X) = F, Br, I). Phenylchlorohydrodigermanes decompose thermally by α-elimination on one germanium atom with formation of germylene and phenylchlorohydrogermane. The physico-chemical IR. and NMR. study of these phenylhalogenohydrodigermanes indicates that, if the vGe? H frequency variations are mostly linked to the inductive effects of the substituents on the same germanium, the variations of the chemical shifts of the Ge? H protons seem to be due to many factors and especially to the inductive effect of the substituents on the germanium and the magnetic anisotropy of the Ge? X bonds.     

Lewis Acid‐Assisted Ene Cyclization of 2‐Azetidinone‐Tethered Enals: Synthesis of Enantiopure Carbacepham Derivatives

Diastereocontrolled Lewis acid‐catalyzed preparation of enantiopure carbacepham derivatives have been developed starting from 2‐azetidinone‐tethered enals. The BF₃?Et₂O‐promoted reaction of alkenylaldehydes 1 and 16 is effective as carbocyclization protocol to afford 4‐substituted 5‐hydroxycarbacephams or 3‐substituted 4,5‐dihydroxycarbacephams, respectively, by a type I carbonyl‐ene reaction, while the BF₃?Et₂O or SnCl₄‐mediated type II carbonyl‐ene cyclization of alkenylaldehydes 2 furnishes 3‐methylene 5‐hydroxycarbacephams along with the corresponding 3‐halo 5‐hydroxycarbacepham. The stereochemical outcome of these carbonyl‐ene cyclizations leading to carbacepham derivatives can be explained in terms of six‐membered, cyclic chair‐like transition‐state models. The formation of halocarbacepham derivatives is proposed to proceed by a stepwise mechanism.     

A Germylene/Borane Lewis Pair and the Remarkable C=O Bond Cleavage Reaction toward Isocyanate and Ketone Molecules

A germylene/borane Lewis pair ( 2 ) was prepared from a 1,1‐carboboration of amidinato phenylethynylgermylene ( 1 ) by B(C₆F₅)₃. Compound 2 reacted with iPrNCO and (4‐MeOC₆H₄)C(O)Me, respectively, with cleavage of the C=O double bond. In the first instance, O and iPrNC insert separately into the Ge?B bond to yield a GeBC₂O‐heterocycle ( 3 ) and a GeBC₃‐heterocycle ( 4 ). In the second case (4‐MeOC₆H₄)(Me)C inserts into the Ge?N bond of 2 while O is incorporated in the Ge?B bond to form a Ge‐centered spiroheterocycle ( 5 ). The reaction of 2 with tBuNC to give 6 , which has almost the same structure as 4 , proved the formation of the isonitrile during transformation from 2 and iPrNCO to 3 and 4 . The kinetic study of the reaction of 2 and iPrNCO gave evidence of proceeding through a GeBC₃O‐heterocycle intermediate. In addition, a DFT study was performed to elucidate the reaction mechanism.     

Trichloro- and methyldichlorogermyl monochelates and dibromo- and dichlorogermyl bischelates derived from N,N-disubstituted amides of 2-hydroxycarboxylic acids

The reactions of GeCl₄, GeBr₄, and MeGeCl₃ with O-trimethylsilyl derivatives of N,N-disubstituted amides of 2-hydroxycarboxylic acids afforded pentacoordinate and hexacoordinate neutral (O,O)-mono- and (O,O)-bischelates. The reactions of glycolic acid derivatives with GeX₄ produced bischelates X₂Ge[OCH₂C(O)NR²R³]₂ 7a,c,d (X = Cl, R² = R³ = Me (a), (CH₂)₅ (c), (CH₂CH₂)₂O (d)) and 8a (X = Br). By contrast, the reactions of lactic and mandelic acid derivatives with GeCl₄ and MeGeCl₃ gave monochelates Cl₃Ge[OCH(R¹)C(O)NR²R³] (S)-9a–c (R¹ = Me) and Cl₂MeGe[OCH(R¹)C(O)NR²R³] 10a (R¹ = H), (S)-11a,b (R¹ = Me), and (S)-12a (R¹ = Ph) (R²R³ = (CH₂)₄ (b)), respectively. According to the X-ray diffraction data, the Ge atom in bischelates 7c,d and 8a has a coordination number 6, and its coordination polyhedron can be described as a slightly distorted octahedron. In monochelates (S)-9a-c, 10a, (S)-11a,b, and (S)-12a, the Ge atom has a coordination number 5, and its coordination polyhedron can be described as a trigonal bipyramid with two halogen atoms or one halogen atom and one ethereal oxygen atom in equatorial positions and the halogen atom and the amide oxygen atom in the axial positions. The bonds in the axial positions are somewhat longer than the corresponding bonds in tetracoordinate Ge compounds.     

Synthesis and Properties of the Alkyl/Aryl Germanium Dioximates Containing Ge─O Bond: Stability Factors—A Theoretical Approach

The reactions of R₂GeCl₂ and R₃GeCl with 9,10‐phenanthrenequinone dioxime in 1:1 and 1:2 molar ratios to form a series of organogermanium complexes of the general formula R₂GeL and (R₃Ge)₂L [R=Me, Et, Ph] have been investigated. The physical and spectral properties of all derivatives are described. In addition, the nature of Ge─O bond has been studied by using the DFT/B3LYP method.     

Etude des composés d'addition d'acides de Lewis,XXXVII [1] composés d'addition de quelques quinones avec TiCl4, et relation entre les fréquences carbonyle et diverses grandeurs physicochimiques

1:1 or 1:2 solid stoichiometric adducts of TiCl₄ with anthraquinone-1,4, anthraquinone-1,2, naphtacenequinone-5,12, pentacenequinone-6,13 have been prepared. The very important lowering Δω(C?O) of the respective IR. carbonyl frequencies, ranging from ?160 to ?100 cm^?1, shows that the acceptor is linked by a dative bond to the carbonyl oxygen atom acting as donor. On the basis of calculations and various considerations, the reduction of the C?O double bond character is confirmed. Linear relations are found to exist between the oxydo-reduction or the polarographic reduction potential of the quinones, and their antisymetric ω_a(C?O) frequencies, the values of Δω, and the O → Ti vibrations, respectively.     

Acyl iodides in organic synthesis: VII. Reactions with trialkyl(alkynyl)silanes,-germanes, and-stannanes

Reactions of acyl iodides R¹COI (R¹=Me, Ph) with trialkyl(alkynyl)silanes,-germanes, and stannanes (R²C≡CMR ₃ ³ ; M=Si, Ge, Sn) were studied. Acyl iodides reacted with the germanium and tin derivatives with cleavage of the M-C_sp bond and formation of the corresponding trialkyl(iodo)germanes and-stannanes R ₃ ³ MI (M=Ge, Sn) and alkynyl ketones R¹C(O)C≡CR² and R¹C(O)C≡CC(O)R¹. By contrast, the reaction of acetyl iodide with ethynyl(trimethyl)silane gave only a small amount of 1,2-diiodovinyl(trimethyl) silance as a result of iodine addition at the triple bond. Bis(trimethylsilyl)ethyne failed to react with acetyl iodide.     

Convenient Synthesis of 2-Aminothiophene Derivatives by Acceleration of Gewald Reaction Under Ultrasonic Aqueous Conditions

Under ultrasound irradiation and in the presence of H₂O/Et₂NH, ethyl cyanoacetate or malononitrile can combine with α-methylene carbonyl compounds and elemental sulfur to efficiently yield 2-aminothiophene derivatives within a few minutes. Products are easily obtained by simple filtration because of their spontaneous precipitation in the reaction mixtures.