The N-alkyl-C-polyfluoroalkyl-C-chlorosulfinimides RFC(Cl)SN R have been investigated. Some aspects of their thermal stability and their [3 + 2] and [3 + 1] cycloaddition reactions have been examined. 相似文献
Trimethylsilyltrifluoromethane sulfonate is shown to be an efficient catalyst for the elimination of Me3SiCl from N-trimethylsilyl-N-(2,4,6-tri-tert-butylphenyl)amidochlorophosphites la-f , leading to the phosphenimidous esters 3a–f. The crystal structures of phosphites 1a and 1d provide a stereochemical explanation for the better thermal stability of 1d On the basis of these observations a convenient and general synthesis of phosphenimidous esters 3a–f is presented. 相似文献
The existence of the orbital interaction presented in the literature as being the cause for the stabilisation of the Z,Z configuration of Ph-S-N=S=N-S-Ph (1) and its derivatives in the crystal phase, has been investigated. The results of theoretical calculations at the DFT/B3LYP/6-311+G* level of theory suggest that such a stabilising interaction might not exist or be extremely weak and that packing forces must be the main cause of the observed Z,Z configuration in the solid. To reach this conclusion structural and energetic parameters were combined to study the bonding in these -S-N=S=N-S- systems. For the analogous Ph-Se-N=S=N-Se-Ph (2) in particular the isomeric equilibrium in solution found in the variable-temperature 77Se NMR spectrum indicates that, in the gas phase or in solution, the observed Z,Z configuration is not stabilised to a greater extent than the Z,E configuration. 相似文献
The structures and energetics of eight substituted bis(thiocarbonyl)disulfides (RCS2)2, their associated radicals RCS2., and their coordination compounds with a lithium cation have been studied at the G3X(MP2) level of theory for R=H, Me, F, Cl, OMe, SMe, NMe2, and PMe2. The effects of substituents on the dissociation of (RCS2)2 to RCS2. were analyzed using isodesmic stabilization reactions. Electron‐donating groups with an unshared pair of electrons have a pronounced stabilization effect on both (RCS2)2 and RCS2.. The S? S bond dissociation enthalpy of tetramethylthiuram disulfide (TMTD, R=NMe2) is the lowest in the above series (155 kJ mol?1), attributed to the particular stability of the formed Me2NCS2. radical. Both (RCS2)2 and the fragmented radicals RCS2. form stable chelate complexes with a Li+ cation. The S? S homolytic bond cleavage in (RCS2)2 is facilitated by the reaction [Li(RCS2)2]++Li+→2 [Li(RCS2)].+. Three other substituted bis(thiocarbonyl) disulfides with the unconventional substituents R=OSF5, Gu1, and Gu2 have been explored to find suitable alternative rubber vulcanization accelerators. Bis(thiocarbonyl)disulfide with a guanidine‐type substituent, (Gu1CS2)2, is predicted to be an effective accelerator in sulfur vulcanization of rubber. Compared to TMTD, (Gu1CS2)2 is calculated to have a lower bond dissociation enthalpy and smaller associated barrier for the S? S homolysis. 相似文献
Copper‐catalyzed Ullmann condensations are key reactions for the formation of carbon–heteroatom and carbon–carbon bonds in organic synthesis. These reactions can lead to structural moieties that are prevalent in building blocks of active molecules in the life sciences and in many material precursors. An increasing number of publications have appeared concerning Ullmann‐type intermolecular reactions for the coupling of aryl and vinyl halides with N, O, and C nucleophiles, and this Minireview highlights recent and major developments in this topic since 2004. 相似文献
The transformation of C? H bonds into other chemical bonds is of great significance in synthetic chemistry. C? H bond‐activation processes provide a straightforward and atom‐economic strategy for the construction of complex structures; as such, they have attracted widespread interest over the past decade. As a prevalent directing group in the field of C? H activation, the amide group not only offers excellent regiodirecting ability, but is also a potential C? N bond precursor. As a consequence, a variety of nitrogen‐containing heterocycles have been obtained by using these reactions. This Focus Review addresses the recent research into the amide‐directed tandem C? C/C? N bond‐formation process through C? H activation. The large body of research in this field over the past three years has established it as one of the most‐important topics in organic chemistry. 相似文献
Catalytic insertion or addition of a metal‐imido/nitrene species, generated from reaction of a transition‐metal catalyst with iminoiodanes, to C? H and C?C bonds offers a convenient and atom economical method for the synthesis of nitrogen‐containing compounds. Following this groundbreaking discovery during the second half of the last century, the field has received an immense amount of attention with a myriad of impressive metal‐mediated methods for the synthesis of amines and aziridines having been developed. This review will cover the significant progress made in improving the efficiency, versatility and stereocontrol of this important reaction. This will include the various iminoiodanes, their in situ formation, and metal catalysts that could be employed and new ligands, both chiral and non‐chiral, which have been designed, as well as the application of this functional group transformation to natural product synthesis and the preparation of bioactive compounds of current therapeutic interest. DOI 10.1002/tcr.201100018 相似文献
M4X3[Si2O7]-Type Lanthanide Chalcogenide Disilicates (M ? Ce? Er; X ? S, Se) Attempts to produce single crystals of MSe2 (or MSe2?X) by vapour phase transport with iodine or the oxidation of MCl2 (or MClH) with sulfur in the presence of NaCl in sealed evacuated quartz containers often yielded well-grown single crystals with the composition M4X3[Si2O7] (M ? pr, Sm, Gd, X ? Se, and M ? Nd, Er, X ? S) as by-products. The crystal structures (tetragonal, 141/amd (no. 141)), Z = 8, contain two crystallographically independent M3+ Cations that are interconnected by chalcogenide (X2?) and disilicate anions ([Si2O7]6?). (M1)3+ is surrounded by eight (five X2? and three terminal O2? of the disilicate group), (M2)3+ by nine (three X2? and six terminal O2? of the [Si2O7]6? anion) chalcogenide anions. The disilicate anion itself exhibits the eclipsed conformation with non-linear Si? O? Si bridges (angles: 128 – 133°). 相似文献
A new unsymmetrical geminal dianion that contained both a phosphine oxide moiety and a phosphine sulfide moiety has been synthesized. Its reactivity towards RuII was explored, which led to the formation of a highly reactive carbene complex that evolved at room temperature to yield a kinetic orthometalated RuII complex through C? H activation of the phenyl group of the phosphine oxide moiety. This insertion was found to be thermally reversible and a second C? H insertion occurred at a phenyl group of the phosphine sulfide moiety to form the thermodynamic orthometalated RuII complex in a diastereospecific manner. DFT calculations fully rationalized the experimental findings in terms of the relative energies of the kinetic and thermodynamic products and allowed the mechanism of this process to be fully understood. 相似文献
Wet oxygenase models : Unprecedented high levels of water incorporation into products (up to 75 %) is observed in epoxidation reactions with H2O2 by a bioinspired nonheme iron catalyst. A surprising substrate‐dependent incorporation of water is observed, and is proposed to arise from fast equilibrium between two high‐valent HO? FeV?O isomeric species exhibiting different reactivity.
An ortho‐selective C F bond borylation between N‐heterocycle‐substituted polyfluoroarenes and Bpin‐Bpin with simple and commercially available [Rh(cod)2]BF4 as a catalyst is now reported. The reaction proceeds under mild reaction conditions with high efficiency and broad substrate scope, even toward monofluoroarene, thus providing a facile access to a wide range of borylated fluoroarenes that are useful for photoelectronic materials. Preliminary mechanistic studies reveal that a RhIII/V catalytic cycle via a key intermediate rhodium(III) hydride complex [(H)RhIIILn(Bpin)] may be involved in the reaction. 相似文献
The Morita? Baylis? Hillman (MBH) reactions of (4S,5R,7R,8R)‐ and (4R,5R,7R,8R)‐4‐hydroxy‐7,8‐dimethoxy‐7,8‐dimethyl‐6,9‐dioxaspiro[4.5]dec‐2‐en‐1‐ones ( 2 and 3 , resp.) with aldehydes using various catalysts were studied. A combination of Bu3P/phenol in THF was found being optimum conditions giving the corresponding MBH adducts with high diastereoisomeric ratios. After separation, each stereomerically pure isomer of the MBH adducts was subjected to hydrolysis employing 1% aq. CF3COOH (TFA) in a water bath of an ultrasonic cleaner to afford the corresponding polyhydroxylated cyclopentenones in good yields. 相似文献