Acetonitrile (CH3CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C?H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C?H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH???N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp2 and sp3 bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C?H can be activated by high pressure, even at room temperature and without a catalyst. 相似文献
Batch and semibatch styrene polymerizations are carried out using a heterogeneous ATRP catalyst system that provides excellent molecular‐weight control. The observed initiator efficiency is lower for semibatch operation due to the high initiator concentrations required to make a low‐MW polymer. Experiments verified that the insoluble metal complex does not participate in the polymerization and that Cu(I) solubility is an order of magnitude higher than that of Cu(II). A mechanistic model, using kinetic coefficients from literature and the solubility data from this study, provides a good representation of the experimental results.
A selective and mild method for the benzylic fluorination of aromatic azaheterocycles with Selectfluor is described. These reactions take place by a previously unreported mechanism, in which electron transfer from the heterocyclic substrate to the electrophilic fluorinating agent Selectfluor eventually yields a benzylic radical, thus leading to the desired C?F bond formation. This mechanism enables high intra‐ and intermolecular selectivity for aza‐heterocycles over other benzylic components with similar C?H bond‐dissociation energies. 相似文献
The simultaneous chain‐growth and step‐growth polymerization of a monomer is of great interest and importance because it can produce unique macromolecules which are difficult to prepare by other means. However, such a transformation is usually difficult to achieve in one polymerization system because chain‐growth polymerization and step‐growth polymerization proceed by different reaction mechanisms. Reported here is the simultaneous chain‐growth and step‐growth polymerization of para‐ and meta‐methoxystyrenes catalyzed by half‐sandwich rare‐earth alkyl complexes, and the step‐growth polymerization proceeds by the C?H polyaddition of anisyl units to vinyl groups. This unprecedented transformation affords a new family of macromolecules containing unique alternating anisole‐ethylene sequences. In contrast to para‐ and meta‐methoxystyrenes, ortho‐methoxystyrene exclusively undergo syndiospecific, living chain‐growth polymerization by continuous C=C bond insertion to give perfect syndiotactic poly(ortho‐methoxystyrene) with high molecular weight and narrow polydispersity (rrrr >99 %, Mn up to 280 kg mol?1, Mw/Mn <1.10). 相似文献
Summary: Two multifunctional iniferters, 1,4-bis-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (BDCIB) and 1,3,5-tris-(α-N,N-diethyldithiocarbamyl-isobutyryloxy)-benzene (TDCIB), were successfully synthesized and used as initiators to initiate the polymerization of styrene in the presence of a CuBr/PMDETA complex. The polymerization results demonstrated that the kinetic plots in all cases were first-order to the monomer, the molecular weight of the polymers increased linearly with the monomer conversion; meanwhile, the molecular weight distribution of the polymer was kept to a very low value (Mw/Mn ≤ 1.35). Furthermore, the measured molecular weights were very close to the calculated values, which indicated the high efficiency of the initiator for the polymerization of styrene. The effect of catalyst concentration and initiator concentration was not obvious and the influence of polymerization temperature was apparent, and the polymerization rate increased with the polymerization temperature. The results of chain-extension and 1H NMR analysis proved that the polymer obtained was capped with diethylthiocarbamoylthiy (DC) group. 相似文献
Axial‐to‐central chirality transfer is an important strategy to construct chiral centers, where the axially chiral reagents are mostly limited to atropomerically stable ones. Reported herein is a RhIII‐catalyzed enantioselective spiroannulative synthesis of nitrones. The coupling proceeds via C?H arylation to give an atropomerically metastable biaryl, followed by intramolecular dearomative trapping under oxidative conditions with high degree of chirality transfer. 相似文献
Cp*RhIII/IrIII complexes are known to play important roles in both C?H activation and transfer hydrogenation (TH). However, these two areas evolved separately. They have been integrated in redox‐ and chemodivergent coupling reactions of N‐pyridylanilines with enones. The iridium‐catalyzed coupling with enones leads to the efficient synthesis of tetrahydroquinolines through TH from iPrOH. Counterintuitively, iPrOH does not serve as the sole hydride source, and the major reaction pathway involves disproportionation of a dihydroquinoline intermediate, followed by the convergent and iterative reduction of quinolinium species. 相似文献
The reactivity of the cationic gold carbide [AuC]+ (bearing an electrophilic carbon atom) towards methane has been studied using Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). The product pairs generated, that is, Au+/C2H4, [Au(C2H2)]+/H2, and [C2H3]+/AuH, point to the breaking and making of C?H, C?C, and H?H bonds under single‐collision conditions. The mechanisms of these rather efficient reactions have been elucidated by high‐level quantum‐chemical calculations. As a major result, based on molecular orbital and NBO‐based charge analysis, an unprecedented hydride transfer from methane to the carbon atom of [AuC]+ has been identified as a key step. Also, the origin of this novel mechanistic scenario has been addressed. The mechanistic insights derived from this study may provide guidance for the rational design of carbon‐based catalysts. 相似文献
Copolymerization of styrene (St) with N-phenylmaleimide(NPMI) was studied with rare earth coordination catalyst Nd(naph)3-AlEts in toluene. Characterization of the copolymers showed that the copolymers possess an alternating structure. 相似文献
Herein, we report a cooperatively palladium/norbornene‐catalyzed polymerization, which simplifies the synthesis of functional aromatic polymers, including conjugated polymers. Specifically, an A2B2C‐type multicomponent polymerization that is based on an ortho amination/ipso alkynylation reaction was developed for the preparation of various amine‐functionalized arylacetylene‐containing polymers. Within a single catalytic cycle, the amine side chains are site‐selectively installed in situ by C?H activation during the polymerization process, which represents a major difference from conventional cross‐coupling polymerizations. This “in situ functionalization” strategy enables the modular incorporation of functional side chains starting from simple monomers, thereby conveniently affording a diverse range of functional polymers. 相似文献
Polyvinylpyridines are an important class of polymers that exhibit interesting properties due to the presence of the nitrogen atom in the pyridine ring. The weakly basic nitrogen atom makes possible a variety of reactions on vinylpyridine polymers, e.g. reaction with acids, quaternization and complexation of metals. In addition, these polymers are mainly attractive in applications as polyelectrolytes, polymeric reagents etc. Few papers about polymerization of 4-vinylpyridine (4-Vpy) with co… 相似文献