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NHC-catalysed[3+2]-asymmetric annulation between pyrazolin-4,5-diones and enals:synthesis of novel spirocyclic pyrazolone γ-butyrolactones and computational study of mechanism and stereoselectivity

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Organic Chemistry Frontiers 2022年第2期9卷 420-427页

作者： Marta gil-Ordonez Alicia Maestro pablo Ortega pablo g.jambrina Jose M.Andres gIR-SintACat-Instituto Universitario CINQUIMA y Departamento de Química Orgánica Facultad de CienciasUniversidad de ValladolidPaseo Belén 747011 ValladolidSpain Departamento de Química Física University of Salamanca37008 SalamancaSpain

Chiral pyrazolones with a spirocyclic centre at the C4-position are widely found in a large family of medically relevant *** recent years,organocatalysis,particularly that performed with quiral N-heterocyclic carbenes(NHCs),has allowed the enantioselective synthesis of these spirocyclic compounds despite its inherent *** this work,we describe the fully diastereo-and highly enantioselective synthesis of novel spirocyclic pyrazolone γ-butyrolactones via NHC-catalysed[3+2]annulation reaction of enals and 1H-pyrazol-4,*** understand the catalytic mechanism and origin of stereoselectivity,electronic structure calculations were carried *** considering various pathways,we concluded that the stereoselectivity-determining step is the formation of the lactone that proceeds after addition of the NHC derived homoenolate to the electrophilic carbonyl group of pyrazolin-4,*** calculations predict that the free energy barrier is lower for the(RS)product,which is also the main product experimentally obtained.

关键词： synthesis spiro mechanism

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CHARACTERISATION OF RATIONAL AND NURBS DEVELOPABLE SURFACES IN COMPUTER AIDED DESIgN

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Journal of Computational Mathematics 2021年第4期39卷 556-573页

作者： Leonardo Fernandez-jambrina ETSI Navales Universidad Politecnica de Madrid28040-MadridSpain

In this paper we provide a characterisation of rational developable surfaces in terms of the blossoms of the bounding curves and three rational functions∧,M,ν.Properties of developable surfaces are revised in this *** particular,a closed algebraic formula for the edge of regression of the surface is obtained in terms of the functions∧,M,ν,which are closely related to the ones that appear in the standard decomposition of the derivative of the parametrisation of one of the bounding curves in terms of the director vector of the rulings and its *** is also shown that all rational developable surfaces can be described as the set of developable surfaces which can be constructed with a constant∧,M,ν.The results are readily extended to rational spline developable surfaces.

关键词： NURBS Bezier Rational Spline NURBS Developable surfaces

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DEVELOPABLE SURFACE PATCHES BOUNDED BY NURBS CURVES

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Journal of Computational Mathematics 2020年第5期38卷 715-731页

作者： Leonardo Fernandez-jambrina Francisco Perez-Arribas ETSI Navales Universidad Polit´ecnica de Madrid28040-MadridSpain

In this paper we construct developable surface patches which are bounded by two rational or NURBS curves,though the resulting patch is not a rational or NURBS surface in *** is accomplished by reparameterizing one of the boundary *** reparameterization function is the solution of an algebraic *** the relevant case of cubic or cubic spline curves,this equation is quartic at most,quadratic if the curves are B´ezier or splines and lie on parallel planes,and hence it may be solved either by standard analytical or numerical methods.

关键词： NURBS B´ezier Rational,Spline NURBS Developable surfaces

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Interpolation of a spline developable surface between a curve and two rulings

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Frontiers of Information Technology & Electronic Engineering 2015年第3期16卷 173-190页

作者： Alicia CANTóN Leonardo FERNáNDEZ-jambrina ETSI Navales Universidad Politécnica de MadridArco de la Victoria 4Madrid 28040Spain

In this paper we address the problem of interpolating a spline developable patch bounded by a given spline curve and the first and the last rulings of the developable surface. To complete the boundary of the patch, a second spline curve is to be given. Up to now this interpolation problem could be solved, but without the possibility of choosing both endpoints for the rulings. We circumvent such difficulty by resorting to degree elevation of the developable surface. This is useful for solving not only this problem, but also other problems dealing with triangular developable patches.

关键词： Developable surfaces Spline surfaces Blossoms

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