利用李代数构造非线性可积及双可积哈密顿耦合

With the help of a Lie algebra,two kinds of Lie algebras with the forms of blocks are introduced for generating nonlinear integrable and bi-integrable couplings.For illustrating the application of the Lie algebras,an integrable Hamiltonian system is obtained,from which some reduced evolution equations are presented.Finally,Hamiltonian structures of nonlinear integrable and bi-integrable couplings of the integrable Hamiltonian system are furnished by applying the variational identity.The approach presented in the paper can also provide nonlinear integrable and bi-integrable couplings of other integrable system.     

UC Pd: A New Form of Pd/C for Sonogashira Couplings

Screening of different sources of Pd/C shows reagents of highly variable nanoparticle sizes and oxidation states of the metal. Typically, catalysts with higher surface area are viewed as likely to be the more reactive. In this paper a new form of Pd/C, “UC Pd” is described that is shown to contain larger nanoparticles yet it is the most reactive catalyst of those sold commercially for Sonogashira coupling reactions. UC Pd functions efficiently in the absence of a copper co‐catalyst, under very mild and “green” conditions using inexpensive 95 % EtOH at 50 °C. It is also the only form of Pd/C that can be recycled. In side‐by‐side reactions with several commercially available forms of Pd/C, none compete successfully with UC Pd under standardized conditions. Physical data obtained from extensive surface analysis using TEM, XRD, XPS, and CO‐TPD measurements lead to an explanation behind the unique reactivity of this new recyclable form of Pd/C.     

Optimized 1D double quantum filter NMR experiments

We propose and demonstrate a 1D pulse sequence to convert double quantum coherence (DQC) of y phase with optimal efficiency, relying on single transition selection. Our sequence has a larger high-sensitivity bandwidth with respect to the coupling, compared to other reconversion strategies. A modified version of the new pulse sequence provides the missing chemical shift and coupling information, at minor cost in sensitivity. Application to 1D 13C INADEQUATE is demonstrated.Our new sequence is also applied to quadrupole coupled spin-1 systems, such as 2H in lyotropic phase. Performance of the sequence may be fine-tuned by pulse flip angle optimization, taking into account relaxation effects.     

An integrable coupling hierarchy of the Mkdv_integrable systems, its Hamiltonian structure and corresponding nonisospectral integrable hierarchy

A four-by-four matrix spectral problem is introduced, locality of solution of the related stationary zero curvature equation is proved. An integrable coupling hierarchy of the Mkdv_integrable systems is presented. The Hamiltonian structure of the resulting integrable coupling hierarchy is established by means of the variational identity. It is shown that the resulting integrable couplings are all Liouville integrable Hamiltonian systems. Ultimately, through the nonisospectral zero curvature representation, a nonisospectral integrable hierarchy associated with the resulting integrable couplings is constructed.     

SEAr-SNAr couplings of indolizines and related pyrrole derivatives with superelectrophilic nitrobenzoxadiazoles

The nucleophilic aromatic substitutions of 7-chloro-4,6-dinitrobenzofurazan (DNBZ-Cl) and 7-chloro-4,6-dinitrobenzofuroxan (DNBF-Cl) with a series of differently substituted indolizines (5a-f) and a series of dihyropyrroloisoquinolines (11a-f) have been investigated. In accord with previous reports emphasizing the superelectrophilic character of these compounds in σ-complexation processes, DNBZ-Cl and DNBF-Cl react very readily and quantitatively with the weak carbon nucleophiles 5a-f and 11a-f at room temperature in acetonitrile. In the case of DNBZ-Cl, the resulting products (7Z,a-f and 12Z,a-f) are those expected from the displacement of the chlorine atom through a S_EAr-S_NAr mechanism. A significant result is that these compounds, despite the lack of coplanarity of the two rings, are characterized by an intense intramolecular charge transfer between the donor pyrrole-type moiety and the electron-deficient acceptor DNBZ moiety. Contrasting with this behaviour, the DNBF-Cl reactions show a totally different pattern, proceeding with loss of the N-oxide functionality and expansion of the pyrrole moiety to afford stable zwitterionic spiro adducts (8F,a-f and 13F,a-f) of a so far unknown type. Rapid NMR recordings have revealed that the formation of these adducts occurs after initial formation of the expected substitution products 7F,a-f and 12F,a-f. A mechanism accounting for the overall rearrangement leading to the spirobenzofurazan adducts is suggested. It is based on an initial nucleophilic attack of the oxygen atom of the N-oxide functionality at the electron-deficient and strongly olefinic C-C coupling bond generated by the aforementioned intramolecular charge transfer. This results in the formation of an unstable five-membered isoxazole ring whose decomposition goes along with loss of the N-oxide functionality and enlargement of the pyrrole moiety into a pyridine one. Also discussed are the factors accounting for the high thermodynamic stability of the spiro adducts, and their relevance to the stability of previously reported spiro adducts.     

Noncommutative integrable coupling system of TC equation hierarchy

A noncommutative version of the TC soliton equation hierarchy is presented, which possesses the zero curvature representation. Then, we show that noncommutative (NC) TC equation can be derived from the noncommutative (anti-)self-dual Yang-Mills equation by reduction. Finally, an integrable coupling system of the NC TC equation hierarchy is constructed by using of the enlarged Lax pairs.     

多类型过程的耦合问题

本文阐述了多类型过程的定义及反应到实践中的具体模型 ,并且证明最优耦合的充要条件 .     

Short and Divergent Total Synthesis of (+)‐Machaeriol B, (+)‐Machaeriol D, (+)‐Δ8‐THC,and Analogues

Short and highly efficient stereoselective syntheses provide machaeriols and cannabinoids in a divergent approach starting from a common precursor, commercially available (S)‐perillic acid. Key features of the novel strategy are a stereospecific palladium‐catalyzed decarboxylative arylation and a one‐pot sequence comprising a stereoselective hydroboration followed by oxidation or reduction of the corresponding intermediary boranes. The divergent approach is convincingly demonstrated by the five‐step syntheses of (+)‐machaeriol B, (+)‐machaeriol D, and related analogues, and the four‐step synthesis of (+)‐Δ⁸‐THC and an analogue.     

Preparation of a Nafion-Teflon bimembrane-supported palladium catalyst and its use in the Heck reaction

A novel palladium catalyst supported on the Nafion membrane, reinforced with poly(tetrafluoroethylene) fiber, has been prepared. The catalyst exhibits high activity and stability in the Heck arylation reactions of aryl iodides with olefins and Sonogashira couplings with phenylacetylene, and can be readily recovered and reused twenty times without significant loss of activity.     

Simplified multiplet pattern HSQC-TOCSY experiment for accurate determination of long-range heteronuclear coupling constants

A new two-dimensional pulse sequence for accurately determining heteronuclear coupling constants is presented. It is derived from HSQC and HECADE techniques with B0 gradient coherence selection. The main feature of the proposed method is spectra with only one component of the IS doublet; i.e., the final result is equivalent to a selective broadband excitation of either Salpha or Sbeta spin states and a preservation of these states during the entire experiment. The effect is obtained by an appropriate combination of in- and antiphase coherences. It is demonstrated that heteronuclear single-bond as well as long-range coupling constants and their relative signs are readily evaluated. The proposed sequence is equally or less sensitive to a variation of heteronuclear one-bond couplings than previously published, closely related sequences. The new method is applied to a peptide sample for determination of 3JN, Hbeta.