Silicon—nitrogen bond cleavage in N-(dimethylimidosilylmethyl)imides and dimethyl(lactamomethyl)aminosilanes with BF3 etherate as an alternative route to N-(dimethylf luorosilylmethyl)imides and related compounds

N-(Dimethylfluorosilylmethyl)succinimide (2a) and N-(dimethylfluorosilylmethyl)phthalimide (2b) were synthesized by the Si—N bond cleavage in readily accessible N-(dimethylimidosilylmethyl)imides with BF₃ etherate. Analogously, (O→Si)-chelated 1-(dimethylfluorosilylmethyl)-2-pyrrolidone was prepared from 1-(dimethylmorpholinosilylmethyl)-2-pyrrolidone. X-ray diffraction study demonstrated that the silicon atom in the crystals of 2b is pentacoordinated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 558–561, March, 2006.     

Synthesis and crystal and molecular structures of six-coordinate tin dibromides and diiodides containing lactamomethyl C,O-chelating ligands

New (O−Sn)-bischelate bis(lactamomethyl)dibromo- and-diiodostannanes [L⁽ⁿ⁾]₂SnX₂ (L is the bidentate lactamomethyl C,O-chelating ligand;n is the size of the lactam ring, 5–7; X=Br or I) were prepared both by the direct method from metallic tin and the correspondingN-(halomethyl)lactams and by the reactions of dichlorides [L⁽ⁿ )]₂SnCl₂ with lithium halides. According to the data of X-ray diffraction analysis, the tin atom in [L⁽ⁿ⁾]₂SnBr₂ (n=5–7) and [L⁽ⁿ⁾]₂SnI₂ (n=5 or 6) adopts an octahedral configuration with the carbon atoms intrans positions and the coordinating oxygen and halogen atoms incis-positions with respect to each other. A comparison with the structures of analogous lactamomethyl halide derivatives of five-and six-coordinate Si, Ge, and Sn demonstrates that the spatial structures of the hypervalent fragments containing six-coordinate atoms are less sensitive to the replacement of the halide ligands and the central atom. The covalence of the M−Hal bond increases and the covalence of the M−O bond decreases in the series M=Si, Ge, and Sn. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1988–1998, October, 1999.     

Synthesis and some chemical properties of 4-acyl-2,6-disilapiperazines. Molecular and crystal structure of 4-formyl-2,2,6,6-tetramethyl-2,6-disilapiperazine

An one-pot synthesis of 4-acyl-2,6-disilapiperazines has been developed which consists of treatment of carboxamides with hexamethyldisilazane and dimethylchloromethylchlorosilane mixture with subsequent amination of the intermediate N,N-bis(dimethylchlorosilylmethyl)amides (which are derivatives of pentacoordinated silicon) with ammonia or primary amines. The hydrolytic stability of the 4-acyl-2,6-disilapiperazines and their reactions with benzenesulfonamide have been studied. The structure of 4-formyl-2,2,6,6-tetramethyl-2,6-disilapiperazine has been confirmed by X-ray diffraction analysis.Russian State Medical University, Moscow 117869, Russia     

Mono-C,O-chelated bromo- and triflatosilanes with an amino acid moiety: salts or covalently bonded complexes?

Russian Chemical Bulletin - Derivatives of the amino acids sarcosine and proline – triflates TsN(Me)CH2C(O)N(Me)-CH2SiMe2OTf and Ns–Pro–N(Me)CH2SiMe2OTf (Ns is 4-NO2C6H4SO2)...     

Stereochemical nonrigidity of (O—Ge)-chelate bis[(2-oxo-1-hexahydroazepinyl)methyl]dichlorogermane: substantiation of the dissociative mechanism of chelating ligand exchange

Stereochemical nonrigidity of the hexacoordinated (O—Ge)-chelate bis(2-oxo-1-hexahydroazepinylmethyl)dichlorogermane in CDCl₃ was studied by dynamic NMR. The activation parameters of the intramolecular rearrangement at the coordination center are G ^# ₂₉₈ = 12.3±0.2 kcal mol^–1, H ^# = 16.9±0.2 kcal mol^–1, and S ^# = 15.3±0.7 cal mol^–1 K^–1. The dissociative mechanism of ligand exchange involving the cleavage of the OGe coordination bond is discussed based on the positive entropy of activation.     

N-Alkylation of N-trimethylsilyl derivatives of lactams,amides, and imides with alkyl sulfonates

Russian Chemical Bulletin - The reaction of N-trimethylsilyl derivatives of amides and imides with alkyl sulfonates on heating affords the corresponding N-alkyl derivatives and trimethylsilyl...     

Synthesis and Some Chemical Properties of 2,2-Dimethyl-4-R-1-oxa-4-aza-2-sila-5-benzocycloheptanones

One-pot synthesis of 2,2-dimethyl-4-R-1-oxa-4-aza-2-sila-5-benzocycloheptanones (R = Me, CH₂SiMe₂Cl) from the N-methylamide of salicylic acid and salicylamide, respectively, by treatment of these amides with a mixture of hexamethyldisilazane and dimethylchloromethylchlorosilane was developed. The hydrolysis and other nucleophilic substitution reactions of the resultant seven-membered silacyclanes were studied. In the case of the silacyclane with R = Me, hydrolysis leads to the corresponding disiloxane, while the silacyclane with R = CH₂SiMe₂Cl gives either 2,2,6,6-tetramethyl-4-(2-hydroxybenzoyl)-2,6-disilamorpholine or its hydrochloride, depending on the reaction conditions. The chlorine atom was replaced by fluorine in the silacyclane with R = CH₂SiMe₂Cl. The structures of 2,2,6,6-tetramethyl-4-(2-hydroxybenzoyl)-2,6-disilamorpholine and its hydrochloride as well as 2,2-dimethyl-4-R-1-oxa-4-az! a-2-sila-5-benzocycloheptanones (R = CH₂SiMe₂Cl, CH₂SiMe₂F) were confirmed by X-ray diffraction.