Fullerene C60 promoted photochemical hydroamination reactions of an electron deficient alkyne with trimethylsilyl group containing tertiary N-alkylbenzylamines

C60-promoted photoaddition reactions of N-α-trimethylsilyl-N-alkylbenzylamines with dimethyl acetylenedicarboxylate (DMAD) were carried out.

(3,5-Dimethyl-1H-pyrazol-1-yl)trimethylsilane

The title compound, C8H16N2Si, crystallizes in the the orthorhombic space group P212121 with one molecule in the asymmetric unit. The Si—N bond is 1.782 (2) Å, which is substantially longer than is found in comparable (3,5-dimethylpyrazolyl)silanes. The trimethylsilyl group adopts a staggered conformation with respect to the planar 3,5-dimethylpyrazolyl unit. C—H...N hydrogen bonds between neighboring molecules form a strand of molecules along the b-axis direction.

Understanding the Reactivity of Trimethylsilyldiazoalkanes Participating in [3+2] Cycloaddition Reactions towards Diethylfumarate with a Molecular Electron Density Theory Perspective

A Molecular Electron Density Theory (MEDT) study is presented here for [3+2] cycloaddition (32CA) reactions of three trimethylsilyldiazoalkanes with diethyl fumarate. The presence of silicon bonded to the carbon of these silyldiazoalkanes changes its structure and reactivity from a pseudomonoradical to that of a zwitterionic one. A one-step mechanism is predicted for these polar zw-type 32CA reactions with activation enthalpies in CCl4 between 8.0 and 19.7 kcal·mol−1 at the MPWB1K (PCM)/6-311G(d,p) level of theory. The negative reaction Gibbs energies between −3.1 and −13.2 kcal·mole−1 in CCl4 suggests exergonic character, making the reactions irreversible. Analysis of the sequential changes in the bonding pattern along the reaction paths characterizes these zw-type 32CA reactions. The increase in nucleophilic character of the trimethylsilyldiazoalkanes makes these 32CA reactions more polar. Consequently, the activation enthalpies are decreased and the TSs require less energy cost. Non-covalent interactions at the TSs account for the stereoselectivity found in these 32CA reactions involving the bulky trimethylsilyl group.

An Extremely Efficient Silylated Benzensulfonate Flame Retardant for Polycarbonate

An extremely efficient flame retardant with low water solubility has been developed for bisphenol-A based polycarbonate. Potassium trimethylsilylbenzenesulfonate (KTSS) combining trimethylsilyl and sulfonate groups in its molecule is 7 times less water soluble and 5 times more effective in flame retardancy than potassium benzenesulfonylbenzenesulfonate (KSS), the commercial workhorse for polycarbonate (PC). At a loading of 0.02%, KTSS enables PC to achieve a solid UL-94 V0 rating and a limiting oxygen index (LOI) value of 34.4%, representing an increase of 8.5 units. The extremely high efficiency of KTSS stems from its great migration ability to the burning polymer surface facilitated by trimethylsilyl group, its timely release of active alkaline species that promote the charring process of PC, and the stabilization of char by silicon. In addition to the exceptional flame retardancy, PC/KTSS retains excellent physical properties of PC.

The cyclopropylcarbinyl route to γ-silyl carbocations

The mesylate derivative of cis-1-hydroxymethyl-2-trimethylsilylcyclopropane has been prepared, along with a number of related mesylates and triflates with substituents on the 1-position. These substrates all solvolyze in CD3CO2D to give products derived from cyclopropylcarbinyl cations that undergo further rearrangement to give 3-trimethylsilylcyclobutyl cations. These 3-trimethylsilylcyclobutyl cations are stabilized by a long-range rear lobe interaction with the γ-trimethylsilyl group. When the substituent is electron-withdrawing (CF3, CN, or CO2CH3), significant amounts of bicyclobutane products are formed. The bicyclobutanes are a result of γ-trimethylsilyl elimination from the cationic intermediate that has an unusually long calculated Si–C bond. The solvolysis chemistry of mesylate and triflate derivatives of trans-1-hydroxymethyl-2-trimethylsilylcyclopropane and 1-substituted analogs can be quite different since these substrates do not generally lead to 3-trimethylsilylcyclobutyl cations.

Photoaddition reactions of N-benzylglycinates containing α-trimethylsilyl group with dimethyl acetylenedicarboxylate: competitive formation of pyrroles vs. β-enamino esters

A study was conducted to gain insight into the preparative potential of photosensitized reactions of acyclic N-benzylglycinates containing an α-trimethylsilyl group with dimethyl acetylenedicarboxylate (DMAD).

Tris[2,2,6,6-tetramethyl-8-(trimethylsilyl)benzo[1,2-d;4,5-d′]bis(1,3-dithiol)-4-yl]methanol diethyl ether monosolvate

The title compound, a triarylmethanol, C46H64OS12Si3 1, was synthesized via lithiation of tris-2,2,6,6-tetramethylbenzo[1,2-d;4,5-d′]bis[1,3]dithiol-4-yl-methanol, 2, and electrophilic quenching with trimethylsilyl chloride. The current crystal structure reveals information about the reactivity of this compound and compares well with the structure reported for the unsubstituted parent compound 2 [Driesschaert et al. (2012). Eur. J. Org. Chem. 33, 6517–6525]. The title compound 1 forms molecular propellers and crystallizes in P-1, featuring an unusually long Si—Car bond of 1.910 (3) Å. Moreover, the geometry at the central quaternary carbon is rather trigonal-pyramidal than tetrahedral due to vast intramolecular stress. One trimethylsilyl group is disordered over two positions in a 0.504 (4):0.496 (4) ratio and one S atom is disordered over two positions in a 0.509 (7):0.491 (7) ratio. The contribution of disordered diethyl ether solvent molecule(s) was removed using the PLATON SQUEEZE (Spek, 2015) solvent masking procedure. These solvent molecules are not considered in the given chemical formula and other crystal data.

Bis[μ-N,N′-(pyridine-2,6-diyl)bis(trimethylsilylamido)-1κ2N1,N2;2:3κ2N6:N6]bis(tetrahydrofuran)-2:3κ2O-1-nickel(II)-2,3-lithium(I)

The title complex, [Li2Ni(C11H21N3Si2)2(C4H8O)2], is a trimetallic complex of two LiIcations and a NiIIcation bridged by twoN,N′-(pyridine-2,6-diyl)bis(trimethylsilylamide) ligands that crystallizes in theFdd2 space group. The molecule hasC2rotational symmetry, with the NiIIcation located on the twofold axis. The coordination sphere of the NiIIcation is composed of two amido N and two pyridyl N-atom donors in a distorted square-planar geometry. The LiIcations are coordinated by two amido N-atom donors and a tetrahydrofuran molecule with a long interaction with a pyridyl N-atom donor. The coordinating tetrahydrofuran ligand and a trimethylsilyl group are disordered. Intra- or intermolecular hydrogen bonding, as well as π–π stacking, are not observed between the molecules, likely indicating that weak electrostatic interactions are the dominant feature leading to the crystal structure.