Experimental study and simulation of kinetics of acetophenone hydrosilylation with diphenylsilane in the presence of rhodium complexes in a microreactor

The hydrosilylation of acetophenone with diphenylsilane in a microreactor in the presence of complexes [Rh(cod)Cl]₂ and [Rh(CO)₂(μ-Cl)]₂ and (R)-(-)-cis-mirtanyl- and (R)-(+)-bornylamine in situ was studied, the kinetics simulation of the process was performed, and the multicriteria optimization of the process was carried out. The influence of the micro-mixing effect on the reaction rate was revealed. Best results in the microreactor were obtained for the [Rh(cod)Cl]₂-BornylNH2 catalytic system. It was established that the formation of 1-phenylethanol and related enol silyl ethers are simultaneous competing reactions.     

Synthesis of some substituted 1,3-thiazolines and 1,3-thiazolidines

Sodium salts of 2, 2-dimethyl-4-mercapto-5-oxo-1,3-thiazoline and 2-oxo-3-mercapto-1-thia-4-azaspiro[4.5]dec-3-ene, obtained from a solvate of sodium cyanodithioformate with three molecules of dimethylformamide, acetone, or cyclohexanone in the presence of morpholine, react with chlorothioformic dimethylamide with the formation of 2,2-dimethyl-5-oxo-4-(dimethylaminothiocarbonylthio)-1,3-thiazoline and 2-oxo-3-(dimethylaminothiocarbonylthio)-1-thia-4-azaspiro[4.5]dec-3-ene, respectively, and during acidolysis by hydrochloric acid they are converted to 2,2-dimethyl-5-oxo-4-thiono-1,3-thiazolidine and 2-oxo-3-thiono-1-thia-4-azaspiro[4.5]decane. The latter compounds are facilely phosphorylated by dialkyl chlorophosphonates at the nitrogen atom. The reaction of the solvate of sodium cyanodithioformate with three molecules of dimethylformamide with chloroacetone in the presence of morpho-line occurs anomalously with the formation of cyanothioformic morpholide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2590–2593, November, 1990.     

Phosphines with 2-imidazolium ligands enhance the catalytic activity and selectivity of rhodium complexes for hydrosilylation reactions

Phosphines with 2-imidazolium ligands can specifically vary their physical and chemical properties by altering the attached substituents. Rhodium complexes (1b-7b) exhibited excellent catalytic activity and selectivity for hydrosilylation of olefins. The selectivity of the β-adduct clearly increased when the length of the alkyl chain bound to the imidazolium cation increased. Rhodium complex 1b in BMimPF₆ can be reused without noticeable loss of catalytic activity and selectivity.     

Catalytic asymmetric hydrosilylation of acetophenone with new chiral thiourea ligands containing the (S)-α-phenylethyl group

New chiral thioureas 1–8 containing 1,2-ethylendiamine or trans-1,2-diaminocyclohexane as the carbon skeleton, and containing an (S)-α-phenylethyl group have been prepared (79–98% yield). Thioureas 1–8 were used as ligands for the zinc-based catalyzed asymmetric hydrosilylation of acetophenone with polymethylhydrosiloxane (PMHS). The best result was achieved with monothiourea 1 (up to 75% ee), in toluene and a catalyst load of 5 mol %.     

Asymmetric hydrosilylation of cyclohexa-1,3-diene with trichlorosilane by palladium catalysts coordinated with chiral phosphoramidite ligands

Chiral phosphoramidite ligands prepared from (S)-binaphthol and various secondary amines were examined for the palladium-catalyzed asymmetric hydrosilylation of cyclohexa-1,3-diene with trichlorosilane. With a sterically demanding phosphoramidite bearing bis(diphenylmethyl)amine, the high enantiomeric excess of 87% was achieved, which is the highest enantioselectivity in the hydrosilylation of cyclohexadiene reported to date. The catalytic activity in the present hydrosilylation was high with all of the ligands employed, while the enantioselectivities varied dramatically depending on the dialkylamine moiety of the phosphoramidite ligand.     

Conformational analysis of 1,3-oxathiane

Computer simulation of pathways of conformational isomerization of 1,3-oxathiane molecule carried out with the help of HF/6-31G(d), MP2.6-31G(d)/HF/6-31G(d), and PNE/3z quantum-chemical approximations showed that interconversion between the degenerate in energy chair conformers proceeds through seven independent pathways: directly and via six flexible forms. Potential energy surface contains eight minimum points including chair conformers and enantiomeric pairs of twist forms, and also five transition states, among them different modification of semi-chair, symmetric and unmmetrical boat. Molecular dynamics methods show that flexible forms at room temperature convert into one another and into the chair conformers.     

Selective desulfurization of 1,3-dithianes, -oxathiolanes and -thiazolidines by tributyltin hydride

Selective desulfurization of 2-alkyl-1,3-dithianes, -oxathiolanes, or -thiazolidines 1 with one equivalent of tri-n-butyltin hydride yields acyclic compounds R¹R²CHX(CH₂)_nSSnBu₃ (X = S,O,NH; N= 2,3), (2) which can be destannylated to the corresponding mercaptans 3.     

Hydrosilylation of acetophenone with diphenylsilane in the presence of rhodium(I) complexes with chiral amines

New chiral rhodium complexes cis-[Rh(CO)₂(RNH₂)Cl] [RNH₂ = (R)-(−)-cis-MyrtNH₂, (R)-(−)-MenthylNH₂, (R)-(+)-BornylNH₂] were synthesized and their catalytic properties in reactions of hydrosilylation of acetophenone with diphenylsilane were studied. It was shown that the reaction products were diphenyl-1-phenylethoxysilane, diphenyl-1-phenylvinyloxysilane and 1,1,3,3-tetraphenyldisiloxane. The best catalytic activity displayed (−)-cis-[Rh(CO)₂(MenthNH₂)Cl]. The hydrosilylation of acetophenone with diphenylsilane in the presence of [Rh(CO)₂(μ-Cl)]₂ and [Rh(cod)Cl]₂ and amines in situ was studied. The best ratio amine:complex = 5:1 was established. With the catalytic systems based on [Rh(cod)Cl]₂ or [Rh(CO)₂(μ-Cl)]₂ the activity increased in the series of amines: (R)-(−)-cis-MyrtNH₂ < (R)-(−)-MenthylNH₂ < (R)-(+)-BornylNH₂, and (R)-(−)-MenthylNH₂ < (R)-(+)-BornylNH₂ < (R)-(−)-cis-MyrtNH₂, respectively. The chemoselectivity maximum was observed in the presence of [Rh(cod)Cl]₂ with (R)-(−)-MenthylNH₂ and [Rh (CO)₂(μ-Cl)]₂ with (R)-(+)-BornylNH₂; maximum asymmetric induction was 43.5% ee at the use of [Rh(CO)₂ (μ-Cl)]₂ and (R)-(+)-BornylNH₂.     

Preparation, characterization, and catalytic properties of ruthenium nitrosyl complexes with polypyrazolylmethane ligands

Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl₃] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm^∗)Ru(NO)Cl₃] [Bpm^∗ = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl₂][PF₆] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm^∗)Ru(NO)Cl₂][PF₆] [Tpm^∗ = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm^∗)Ru(NO)Cl₃] (2) and [(Tpm^∗)Ru(NO)Cl₂][PF₆] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.     

Synthesis,spectral characterization and catalytic applications of Ru(II) complexes with amide ligands

Ruthenium(II) complexes of the type, RuCl₂(NO)(PPh₃)(L₂) (where L = amide ligand) have been synthesized and characterized on the basis of their elemental analysis IR, ¹H-, ¹³C-, ³¹P-NMR spectra. Amide ligand behaved as a bidentate ligand. The probable structures of these complexes have been discussed. They were used as catalysts for the hydrolysis of drugs viz. rivastigmine tartrate and neostigmine bromide. The percent yields of hydrolyzed products of these drugs were determined spectrophotometrically.     

Platinum(II) complexes with bidentate iminopyridine ligands: Synthesis,spectral characterization,properties and structural analysis

Four platinum(II) complexes, [PtCl₂L] (L = (4-fluorophenyl)pyridin-2-ylmethylene-amine, 1; (4-chlorophenyl)pyridin-2-ylmethyleneamine, 2; (4-bromophenyl)pyridin-2-ylmethyleneamine, 3 and (4-iodophenyl)pyridin-2-ylmethyleneamine, 4) have been synthesized and characterized by CHN analysis, IR and UV–Vis spectroscopy. The crystal structures of 1 and 2 were determined using single crystal X-ray diffraction. The coordination polyhedron about the platinum (II) center in the complexes is best described as distorted square planar. The complexes undergo stacking to form a zigzag Pt···Pt···Pt chain containing both short (3.57(7) Å in 1 and 3.62(8) Å in 2) and long (5.16(7) Å in 1 and 5.41(9) Å in 2) Pt···Pt separations through the crystal. The compounds absorb moderately in the visible region, owing to a charge-transfer-to-diimine electronic transition. The redox potentials are approximately insensitive to the substituents on the phenyl ring of the ligands.     

Conformational analysis of 3-methyltetrahydro-1,3-oxazine

Conformational analysis of 3-methyltetrahydro-1,3-oxazine has been performed using HF/6-31G(d), PBE/3z, and RI-MP2/λ2 simulation approximations. The potential energy surface contains eight minima. Interconversion of the axial and equatorial chair conformers (main minima) occurs via several independent pathways involving six twist forms. The preferred path presumes direct chair-chair transition via pyramidal inversion of the nitrogen atom.     

Conformational analysis of 1,3-dioxane in nanotubes

Russian Journal of Organic Chemistry - Computer simulation of conformational transformations of 1,3-dioxane molecule within model single-walled carbon nanotubes (hybrid DFT-method PBE/3ζ)...     

Conformational analysis of 5,5-dinitro-1,3-dioxane

Study of conformational transformations of 5,5-dinitro-1,3-dioxane by the method HF/6-31G(d), and also hybrid DFT PBE/3z and RI-MP2/λ2 indicated the only inversion route chair-chair through an intermediate minimum corresponding to the 2,5-twist-form. The potential barrier to this process was estimated and also the features of the intramolecular rotation of the axial and equatorial nitro groups in the chair conformer were investigated.     

Regioselectivity of the hydrolysis of 2-(1-alkoxyvinyl)-substituted imidazolidines, 1,3-thiazolidines,and 1,3-oxazolidines

2-(1-Alkoxyvinyl)-1,3-thiazolidines reacted with H₂O or D₂O in the presence of 105 mol % of p-toluenesulfonic acid or trifluoroacetic acid (20°C, 1 h) to give 2-acetyl-1,3-thiazolidine in quantitative yield. 2-(1-Alkoxyvinyl)-3,5-diphenylimidazolidines underwent hydrolysis in the presence of 20 mol % of an acid (20°C, 24 h) at the vinyloxy group with high regioselectivity yielding 2-acetylimidazolidines. Hydrolysis of 2-(1-alkoxyvinyl)-3-phenyl-1,3-oxazolidines in the presence of 10 mol % of p-toluenesulfonic acid (20°C, 5 days) takes two pathways, one of which involves the endocyclic C-O bond with ring opening and the other involves the vinyloxy group to produce 2-acetyl-3-phenyl-1,3-oxazolidine. Unlike phenyl-substituted 1,3-thiazolidines and imidazolidines, hydrolysis of their 3-methyl- and 3,5-dimethyl-substituted analogs in acid medium occurs mainly via ring opening. The observed hydrolysis pathways were interpreted in terms of B3PW91/6-311G(d,p) quantum-chemical calculations.     

Conformational analysis of 5-substituted 1,3-dioxanes

Quantum-chemical study on the potential energy surface of 5-alkyl- and 5-phenyl-1,3-dioxanes at the RHF/6-31G(d) level of theory revealed two pathways for conformational isomerizations of the equatorial and axial chair conformers. Potential barriers to this process were estimated. The Gibbs conformational energies ΔG° of substituents at C⁵ in the 1,3-dioxane ring were determined on the basis of experimental (¹H NMR) and theoretical vicinal coupling constants, which turned out to be consistent with published data.     

4-Ferrocenyl-1,3-oxazoline derivatives as ligands for catalytic asymmetric allylation reactions

Bis(oxazolines) and 2-(2-phosphinoaryl)oxazolines derived from highly enantiopure 2-amino-2-ferrocenylethanol have been tested as ligands in the asymmetric Pd(0)-catalysed allylic alkylation reaction. Essentially complete enantioselectivity (99.8:0.2 er) has been achieved in the nucleophilic substitution of 1,3-diphenyl-2-propenyl acetate by dimethyl malonate anion. The absolute configuration of the ligands has been unambiguously established by chiroptical methods.