Synthesis of cyclic guanidines

Rapoport, Henry; Rodricks, Joseph V.

doi:10.1021/jo00800a012

Cited by 24 publications

(4 citation statements)

References 7 publications

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“…[73][74][75][76]84 Minimization of g ex ͑x͒ with respect to x ͑neglecting the derivative ‫ץ‬e anh ex / ‫ץ‬x͒ leads to Eq. [73][74][75][76]84 Minimization of g ex ͑x͒ with respect to x ͑neglecting the derivative ‫ץ‬e anh ex / ‫ץ‬x͒ leads to Eq.…”

Section: A Formulation Of the Modelmentioning

confidence: 99%

Gaussian excitations model for glass-former dynamics and thermodynamics

Matyushov

Angell

2007

The Journal of Chemical Physics

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We describe a model for the thermodynamics and dynamics of glass-forming liquids in terms of excitations from an ideal glass state to a Gaussian manifold of configurationally excited states. The quantitative fit of this three parameter model to the experimental data on excess entropy and heat capacity shows that "fragile" behavior, indicated by a sharply rising excess heat capacity as the glass transition is approached from above, occurs in anticipation of a first-order transition--usually hidden below the glass transition--to a "strong" liquid state of low excess entropy. The distinction between fragile and strong behavior of glass formers is traced back to an order of magnitude difference in the Gaussian width of their excitation energies. Simple relations connect the excess heat capacity to the Gaussian width parameter, and the liquid-liquid transition temperature, and strong, testable, predictions concerning the distinct properties of energy landscape for fragile liquids are made. The dynamic model relates relaxation to a hierarchical sequence of excitation events each involving the probability of accumulating sufficient kinetic energy on a separate excitable unit. Super-Arrhenius behavior of the relaxation rates, and the known correlation of kinetic with thermodynamic fragility, both follow from the way the rugged landscape induces fluctuations in the partitioning of energy between vibrational and configurational manifolds. A relation is derived in which the configurational heat capacity, rather than the configurational entropy of the Adam-Gibbs equation, controls the temperature dependence of the relaxation times, and this gives a comparable account of the experimental observations without postulating a divergent length scale. The familiar coincidence of zero mobility and Kauzmann temperatures is obtained as an approximate extrapolation of the theoretical equations. The comparison of the fits to excess thermodynamic properties of laboratory glass formers, and to configurational thermodynamics from simulations, reveals that the major portion of the excitation entropy responsible for fragile behavior resides in the low-frequency vibrational density of states. The thermodynamic transition predicted for fragile liquids emerges from beneath the glass transition in case of laboratory water and the unusual heat capacity behavior observed for this much studied liquid can be closely reproduced by the model.

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Section: A Formulation Of the Modelmentioning

confidence: 99%

Gaussian excitations model for glass-former dynamics and thermodynamics

Matyushov

Angell

2007

The Journal of Chemical Physics

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“…The calculated data were in excellent agreement with the experimental ones. At the same time, Rapoport [5] suggested a similar concept that he called a two-liquid model in order to explain maxima in the Rb and Cs melting curves. The expression for the Gibbs potential in this model was the same as in [3,4] for cerium, the only difference being that the components were clusters rather than atoms.…”

Section: The Model Of the Pseudo-binary Regular Solutionsmentioning

confidence: 99%

A thermodynamic approach toT–Pphase diagrams of substances in liquid and amorphous states

Ponyatovsky

2003

J. Phys.: Condens. Matter

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The metastable phase equilibria of substances in the disordered, liquid or amorphous, state are considered in T–P coordinates. Application of the thermodynamic model of pseudo-binary solutions is illustrated by means of calculated metastable T–P phase diagrams of water, carbon, and semiconducting compounds, GaSb and Ga38Sb38Ge24. All calculated diagrams include the equilibrium lines between the disordered phases terminating at the critical points and the stability boundaries of these phases, the spinodals. Depending on the mutual disposition of the elements of the stable and metastable T–P diagrams, two additional lines of metastable equilibria between the crystalline high-pressure phase and each of the metastable disordered phases can appear. These lines terminate at the points of intersection with spinodals. These special points are denoted as pseudo-critical points. A combined analysis of the stable and metastable diagrams gives a reasonable interpretation of the experimental data on the phase transformations and on the nature of the anomalous properties of the substances in question as well as allowing prediction of some new effects.

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“…Numerous natural products including saxitoxin and monanchorin, members of the pyrrolo-2-aminoimidazole alkaloid family including phakellin, and several drug leads possess cyclic fused or bridged guanidines (Figure a). Reported methods for the synthesis of cyclic guanidines include cyclization of diamines and metal-promoted hydroaminations of propargyl guanidines . Tepe and co-workers reported a N -bromosuccinimide initiated, one-pot annulation of a Boc-guanidine to an alkene in their synthesis of dibromphakellin, indolo-phakellin, and a proteasome inhibitor derivative, bromo-indolo-phakellin .…”

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confidence: 99%

Generation and Reactivity of 2-Amido-1,3-diaminoallyl Cations: Cyclic Guanidine Annulations via Net (3 + 2) and (4 + 3) Cycloadditions

2020

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Toward a method for direct conversion of alkenes to cyclic guanidines, we report that 1,3-dipolar cycloadditions of 2-amido-1,3-diamino allylic cations with alkenes provide a new method for direct cyclic guanidine annulation. Generated under oxidative conditions, the 2-amido-1,3-diaminoallyl cations react as 1,3-dipoles providing rapid access to 2-amino imidazolines through net (3 + 2) cycloadditions. The utility is demonstrated through a concise synthesis of the oroidin alkaloid, phakellin. The described 1,3-dipole also participates in net (4 + 3) cycloadditions with dienes.

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Synthesis of cyclic guanidines

Cited by 24 publications

References 7 publications

Gaussian excitations model for glass-former dynamics and thermodynamics

Gaussian excitations model for glass-former dynamics and thermodynamics

A thermodynamic approach toT–Pphase diagrams of substances in liquid and amorphous states

Generation and Reactivity of 2-Amido-1,3-diaminoallyl Cations: Cyclic Guanidine Annulations via Net (3 + 2) and (4 + 3) Cycloadditions

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