504 research outputs found
Lamprechts Alexander. Nach den drei Texten mit dem Fragment des Alberic von Besançon und den lateinischen Quellen hrsg. u. erkl. von Karl Kinzel
No full textElektronische Reproduktion von: Lamprechts Alexander / nach den drei Texten mit dem Fragment des Alberic von Besançon und den lateinischen Quellen hrsg. u. erkl. von Karl Kinzel. - Halle a.S. : Verl. d. Buchh. d. Waisenhauses, 1884. - LXXX, 543 Seiten. -
Standort: Universität Marburg, Universitätsbibliothek. -
Signatur: 003 GF 2071 A37.884. -
Bemerkungen:
Digitalisiert 202
3-Hydroxy-4-oxo-4H-pyrido[1,2-a]pyrimidine-2-carboxylates-A new class of HIV-1 integrase inhibitors
No full textSupplementary_file_questionnaire – Supplemental material for Tumor Treating Fields for Glioblastoma Treatment: Patient Satisfaction and Compliance With the Second-Generation Optune® System
No full textSupplemental material, Supplementary_file_questionnaire for Tumor Treating Fields for Glioblastoma Treatment: Patient Satisfaction and Compliance With the Second-Generation Optune® System by Adrian Kinzel, Michael Ambrogi, Michael Varshaver and Eilon D Kirson in Clinical Medicine Insights: Oncology</p
Determination of the origin of stereoselectivity in multiple-transition-state reactions using DFT calculations: Enantioselective synthesis of homoallylic alcohols from aliphatic methyl ketones via an auxiliary-mediated allylation
No full textComputational investigations on the highly stereoselective allylation of butanone in the presence of a chiral norpseudoephedrine-derived auxiliary have been performed. They suggest an S(N)1-type mechanism via the attack of allyltrimethylsilane to an intermediately formed oxocarbenium ion. The identification of preferred transition states (TSs) leads to a straightforward rationalization of the observed selectivity which can be extended to analogues of the auxiliary. A screening process has been devised to select 61 potentially relevant TSs from a total of almost 300 theoretically possible TSs. Final results were obtained from gas-phase calculations employing the B3LYP/6-31+G(d) level of theory as well as in dichloromethane solution using the B3LYP/6-311 ++ G(2d,p)//B3LYP/6-31 +G(d) level of theory in combination with polarizable continuum model and the UAKS set of radii. The agreement of theoretically predicted and experimentally observed selectivities is very good in both cases. However, the relative energy differences for several relevant TSs differ significantly when going from gas phase to solution, thus illustrating the necessity of performing calculations in solution to draw correct conclusions
Origin of syn/anti diastereoselectivity in aldehyde and ketone crotylation reactions: A combined theoretical and experimental study
No full textWe report on experimentally determined and computationally predicted diastereoselectivities of (a) multicomponent crotylation (MCC) reactions of simple aliphatic aldehydes and ketones and (b) of acetal substitution (AS) reactions of aldehyde dimethyl acetals with E- and Z-configurated crotyl trimethylsilane to give homoallylic methyl ethers bearing two newly formed stereogenic centers. We found that corresponding MCC and AS reactions give nearly equal syn/anti ratios. While the crotylations of acetaldehyde and propionaldehyde mainly result in the syn product for E-configurated silane and in the anti product for Z-configurated silane, the syn product is found as main product for the crotylation of pivaldehyde regardless of substrate double bond geometry. Using butanone as substrate, the anti product is found as main product in both cases. By computational investigation employing the B3LYP/6-31+G(d) level of theory in dichloromethane solution (PCM/UAKS), we found that the attack of O-methyl-substituted carboxenium ions by crotyl silane explains the experimentally observed selectivities, indicating that these crotylations in fact proceed in an S(N)1-type reaction via this ionic intermediate. Comparison of relevant open transition-state structures leads to a rationalization of the observed selectivities. For all systems studied, three transitionstate conformations are necessary and sufficient to determine the selectivity. This has been confirmed by studying the MCC reactions of isobutyraldehyde. Activation energies for the stereogenic step have been determined by calculation of the transition state and substrate structures in dichloromethane solution at the B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) level of theory in dichloromethane solution. The possibility to predict simple diastereoselectivity in general Lewis acid-mediated crotylations of aldehydes and ketones is discussed
Stereoselective Allylation of Ketones: Explanation for the Unusual Inversion of the Induced Stereochemistry in the Auxiliary‐Mediated Crotylation and Pentenylation of Butanone by DFT Calculations
No full textAuxiliary-mediated domino crotylations and pentenylations of butanone yield homoallylic ethers with two newly formed stereogenic centers. With our norpseudoephedrine-derived auxiliary, we observed the formation of anti isomers exclusively, and the nature of the major isomer was independent of the substrate double bond geometry. Interestingly, there is a switch in induced selectivity when going from crotylation to pentenylation. Here, we present the computational rationalization for this behavior by identification of the relevant transition states (TSs), the energies of which were determined by using the B3LYP/6-31+G(d) level of theory in combination with the PCM/UAKS method to include the effects exerted by the solvent dichloromethane. To quickly narrow down the number of potentially relevant TSs from the whole set of 288 and 864 TSs for the crotylation and pentenylation, respectively, we employed a screening process based on B3LYP//AM1 energies. The predicted selectivities are in good agreement with experimentally determined ones. Furthermore, the obtained results also facilitate an explanation of the selectivities obtained in hexenylations and heptenylations. Finally, activation energies were determined that account for the significantly longer reaction times than those for the domino allylation with unsubstituted trimethylallylsilane.Fonds der Chemischen Industri
sj-docx-2-hej-10.1177_00178969231191085 – Supplemental material for Canadian cannabis education resources to support youth health literacy: A scoping review and environmental scan
No full textSupplemental material, sj-docx-2-hej-10.1177_00178969231191085 for Canadian cannabis education resources to support youth health literacy: A scoping review and environmental scan by Emily J. Howe, Lisa D Bishop, Bethany S. Torraville, Emily C. Rowe, Eden Kinzel and Jennifer R. Donnan in Health Education Journal</p
sj-docx-1-hej-10.1177_00178969231191085 – Supplemental material for Canadian cannabis education resources to support youth health literacy: A scoping review and environmental scan
No full textSupplemental material, sj-docx-1-hej-10.1177_00178969231191085 for Canadian cannabis education resources to support youth health literacy: A scoping review and environmental scan by Emily J. Howe, Lisa D Bishop, Bethany S. Torraville, Emily C. Rowe, Eden Kinzel and Jennifer R. Donnan in Health Education Journal</p
Spontaneous-search method and short-time dynamics: applications to the Domany-Kinzel cellular automaton
No full textThe one-dimensional Domany-Kinzel cellular automaton is investigated by two numerical approaches: (i) the spontaneous-search method, which is a method appropriated for a search of criticality; (ii) short-time dynamics. Both critical frontiers of the system are investigated, namely, the one separating the frozen and active phases, as well as the critical line determined by damage spreading between two cellular automata, that splits the active phase into the nonchaotic and chaotic phases. The efficiency of the spontaneous-search method is established herein through a precise estimate of both critical frontiers, and in addition to that, it is shown that this method may also be used in the determination of the critical exponent ν ⊥ . Using the critical frontiers obtained, other exponents are estimated through short-time dynamics. It is verified that the critical exponents of both critical frontiers fall in the universality class of directed percolation. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200805.70.Ln Nonequilibrium and irreversible thermodynamics, 64.60.Ht Dynamic critical phenomena, 64.60.-i General studies of phase transitions,
- …
