117,706 research outputs found
Highly Enantioselective Carbamate-based Aminolytic Kinetic Resolution (AKR) of Terminal Epoxides
No full textHighly Enantioselective Carbamate-based Aminolytic Kinetic Resolution (AKR) of Terminal Epoxides
P. Melchiorre*, G. Bartoli, A. Carlone, L. Sambri
Department of Organic Chemistry “A. Mangini” - University of BolognaV.le Risorgimento, 4 - 40136 Bologna, ItalyFax +39 051 209 3654, e-mail: [email protected]
Amino alcohol, Asymmetric synthesis, Aziridine, Kinetic resolution, Oxazolidinone
The asymmetric aminolytic kinetic resolution (AKR) of racemic terminal epoxides using carbamates as the nucleophile catalysed by readily available chiral (salen)CoIII complexes affords both aliphatic and aromatic N-Boc or N-Cbz protected 1,2-amino alcohols in almost enantiomerically pure form (ee ≥ 99%).1, 2 The extraordinary high levels of selectivity and the synthetic versatility of the carbamate moiety render the AKR strategy a practical synthetic tool for the direct synthesis of valuable chiral building blocks such as 5-substituted oxazolidinones and N-protected aziridines in enantiomerically pure form starting from inexpensive racemic terminal epoxides. 1. Bartoli, G.; Bosco, M.; Carlone, A.; Locatelli, M.; Melchiorre, P.; Sambri, L. Org. Lett. 2004, 6, 3973.2. For earlier studies involving (salen)Co-catalysed aymmetric ring opening of epoxides, see: Schaus, S. E.; Brandes, B. D.; Larrow, J. F.; Tokunaga, M.; Hansen, K. B.; Gould, A. E.; Furrow, M. E.; Jacobsen, E. N. J. Am. Chem. Soc. 2002, 124, 1307 and references cited therein
Enantioselective organocatalytic approaches to active pharmaceutical ingredients - Selected industrial examples
No full textCatalysis is, often, the preferred approach to access chiral molecules in enantioenriched form both in academia and in industry; nowadays, organocatalysis is recognised as the third pillar in asymmetric catalysis, along with bio- and metal-catalysis. Despite enormous advancements in academic research, there is a common belief that organocatalysis is not developed enough to be applicable in industry. In this review, we describe a selection of industrial routes and their R&D process for the manufacture of active pharmaceutical ingredients, highlighting how asymmetric organocatalysis brings added value to an industrial process. The thorough study of the steps, driven by economic stimuli, developed and improved chemistry that was, otherwise, believed to not be applicable in an industrial setting. The knowledge discussed in the reviewed papers will be an invaluable resource for the whole research community
Industrial Relevance of Asymmetric Organocatalysis in the Preparation of Chiral Amine Derivatives in Methodologies in Amine Synthesis (Eds.: A. Ricci, L. Bernardi)
No full textProvides a unique overview of efficient synthetic routes to one of the most important compound classes in organic and pharmaceutical chemistry!
Amines are among the most important compounds in organic chemistry due to their wide occurrence in natural products, drugs, crop protection compounds, and advanced materials. For example, the majority of drugs are amines or contain functional groups derived from amines. Powerful and efficient methods for the introduction of the amino group are therefore of great importance to synthetic chemists in academia and industry.
Methodologies in Amine Synthesis ? Challenges and Applications presents powerful and state-of-the-art methods for the efficient preparation of amines. It summarizes recent advances in the electrophilic amination reaction, hydroamination, C?H amination as well as newly developed photocatalytic approaches. It further describes organocatalytic and enzymatic routes to the generation of amines under mild and environmentally friendly conditions. In addition, it highlights the relevance of the amino function in bioactive molecules, drugs, and in the engineering of smart materials. Finally, the application of palladium-catalyzed aromatic amination in industrial context is critically discussed.
* Only up-to-date and comprehensive book on the preparation of amines ? one of the most frequently occurring compound classes found in natural products, bioactive molecules, and advanced materials.
* Presents efficient and useful synthetic methods, highlights opportunities/ challenges as well as applications in pharmaceutical chemistry and materials science.
* Chapters are compiled by well-known experts in the field. One of them edited the previous books ?Modern Amination Methods? (2001) and ?Amino Group Chemistry? (2007).
The book Methodologies in Amine Synthesis ? Challenges and Applications is a musthave for chemists in academia and industry working in the field of organic synthesis and catalysis, natural product chemistry, drug synthesis and pharmaceutical chemistry, as well as materials science
Nonlinear Dirac Equation on Graphs with Localized Nonlinearities: Bound States and Nonrelativistic Limit
No full textIn this paper we study the nonlinear Dirac (NLD) equation on noncompact metric graphs with localized Kerr nonlinearities, in the case of Kirchhoff-type conditions at the vertices. Precisely, we discuss existence and multiplicity of the bound states (arising as critical points of the NLD action functional) and we prove that, in the L-2-subcritical case, they converge to the bound states of the nonlinear Schrodinger equation in the nonrelativistic limit
Vibrations of a rail coupled to a foundation beam through a series of discrete elastic supports
No full textIndustrial Relevance of Asymmetric Organocatalysis in the Preparation of Chiral Amine Derivatives in Methodologies in Amine Synthesis (Eds.: A. Ricci, L. Bernardi)
No full textThis chapter covers the emerging utilization of organocatalytic methodologies in industrial settings directed at the large-scale preparation of enantioenriched amines and N-heterocycles. First, some selected manufacturing processes, based on organocatalytic stereodetermining steps, are commented concisely. Despite the generally high catalyst loadings required, these examples show that the relatively low cost of organic catalysts makes the development of cost-effective industrial routes possible. Then, three case studies (pregabalin, the bicyclic core of telaprevir, and 5-(trifluoromethyl)-2-isoxazolines) are discussed. These chiral targets have been approached through a variety of enantioselective strategies, among which the organocatalytic ones stand out for their versatility and potential for scale-up. Recent applications of organocatalysis in industrial settings are not restricted to a single activation mode or a class of catalysts. They encompass the whole catalyst and reaction repertoire typical of this relatively novel catalytic approach to asymmetric synthesis. Asymmetric organocatalysis proves to be, therefore, a useful and versatile synthetic tool for the industrial preparation of chiral compounds
Well-posedness of the two-dimensional nonlinear Schrödinger equation with concentrated nonlinearity
No full textWe consider a two-dimensional nonlinear Schr\"odinger equation with concentrated nonlinearity. In both the focusing and defocusing case we prove local well-posedness, i.e., existence and uniqueness of the solution for short times, as well as energy and mass conservation. In addition, we prove that this implies global existence in the defocusing case, irrespective of the power of the nonlinearity, while in the focusing case blowing-up solutions may arise
Enantioselective organocatalytic approaches to active pharmaceutical ingredients - selected industrial examples
No full textCatalysis is, often, the preferred approach to access chiral molecules in enantioenriched form both in academia and in industry; nowadays, organocatalysis is recognised as the third pillar in asymmetric catalysis, along with bio- and metalcatalysis. Despite enormous advancements in academic research, there is a common belief that organocatalysis is not developed enough to be applicable in industry. In this review, we describe a selection of industrial routes and their RandD process for the manufacture of active pharmaceutical ingredients, highlighting how asymmetric organocatalysis brings added value to an industrial process. The thorough study of the steps, driven by economic stimuli, developed and improved chemistry that was, otherwise, believed to not be applicable in an industrial setting. The knowledge discussed in the reviewed papers will be an invaluable resource for the whole research community
An introduction to the two-dimensional Schrödinger equation with nonlinear point interactions
No full textWe present an introduction to the nonlinear Schroedinger equation (NLSE) with concentrated nonlinearities in R2. Precisely, taking a cue from the linear problem, we sketch the main challenges and the typical difficulties that arise in the twodimensional
case, and mention some recent results obtained by the authors on local and global wellposedness
NLS ground states on the half-line with point interactions
No full textWe investigate the existence and the uniqueness of NLS ground states of fixed
mass on the half-line in the presence of a point interaction at the origin. The
nonlinearity is of power type, and the regime is either -subcritical or
-critical, while the point interaction is either attractive or
repulsive. In the -subcritical case, we prove that ground states exist
for every mass value if the interaction is attractive, while ground states
exist only for sufficiently large masses if the interaction is repulsive. In
the latter case, if the power is less or equal to four, ground states coincide
with the only bound state. If instead, the power is greater than four, then
there are values of the mass for which two bound states exist, and neither of
the two is a ground state, and values of the mass for which two bound states
exist, and one of them is a ground state. In the -critical case, we
prove that ground states exist for masses strictly below a critical mass value
in the attractive case, while ground states never exist in the repulsive case.Comment: 17 page
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