Search results for "combinatorial"
showing 10 items of 1208 documents
ChemInform Abstract: Tandem Cross Enyne Metathesis (CEYM)-Intramolecular Diels-Alder Reaction (IMDAR). An Easy Entry to Linear Bicyclic Scaffolds.
2015
A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.
A combinatorial algorithm for the optimization of refraction seismics data inversion
1993
Abstract The problem of data inversion in refraction seismics can be split in two parts: data first must be preprocessed in order to determine the travel-time curve; this essentially is a geometrical problem, complicated, however, by its pattern recognition aspects. Once the geometrical problem is solved, the second part, the inversion proper, is straightforward, as the soil layering model can be calculated according to well-known algorithms. The more difficult part of the problem is the former, which implies a type of pattern recognition; because of this type of difficulty, the geometrical part of the problem usually is committed to the skill of a human operator. This paper describes an al…
Greedy and K-Greedy algoritmhs for multidimensional data association
2011
[EN] The multidimensional assignment (MDA) problem is a combinatorial optimization problem arising in many applications, for instance multitarget tracking (MTT). The objective of an MDA problem of dimension $d\in\Bbb{N}$ is to match groups of $d$ objects in such a way that each measurement is associated with at most one track and each track is associated with at most one measurement from each list, optimizing a certain objective function. It is well known that the MDA problem is NP-hard for $d\geq3$. In this paper five new polynomial time heuristics to solve the MDA problem arising in MTT are presented. They are all based on the semi-greedy approach introduced in earlier research. Experimen…
Synthesis of rigid ethynyl-bridged polytopic picolinate ligands for MOF applications
2015
Abstract Segmented homopolytopic ligands that consist of a rigid central arylene platform, ethynylene spacers, and terminal chelating picolinate subunits have been synthesized in good yields in a two-step procedure involving a Sonogashira-type cross coupling reaction between the ester methyl 5-bromopyridine-2-carboxylate and several arylacetylenes, followed by hydrolysis of the resulting methyl picolinates. A similar strategy has been employed for the preparation of heteroditopic ligands containing picolinate and a second non-chelating pyridine or benzoate unit. The compounds are potential candidates for organic linkers in metal–organic frameworks (MOFs).
Oxidative (Cross-)Coupling Reactions Mediated by C-H Activation of Thiophene Derivatives by Using Molybdenum(V) Reagents
2014
Oxidative coupling by using molybdenum pentachloride provides fast and modular access to sophisticated thienoacenes in excellent yields. The coupling process can be accomplished with thiophene and benzothiophene derivatives and provides various complex skeletons such as spirocyclic compounds. In this approach, the first cross-coupling reactions with the use of MoCl5 were established and important motifs for semiconducting materials were synthesized.
Enantioselective zinc-mediated conjugate addition of terminal alkynes to enones.
2012
Zinc for conjugate alkynylation: The enantioselective conjugate addition of terminal alkynes to 2-arylidene-1,3-diketones in the presence of diethylzinc and a catalytic amount of (R)-VANOL has been developed. The reaction can be applied to different aromatic and heteroaromatic alkynes and enones, giving the expected products in good yield and with enantiomeric excesses up to 91%. The products can be enantiomerically enriched up to 99% ee by crystallization (see scheme).
Highly selective electrosynthesis of biphenols on graphite electrodes in fluorinated media.
2011
The direct and selective phenol coupling reaction that provides biphenols still represents a challenge in organic synthesis. The recently developed electrosynthesis on boron-doped diamond anodes with fluorinated additives was developed further to allow the application to less-expensive electrodes and fluorinated media. This advanced protocol allows the highly selective anodic phenol coupling reaction on graphite with a broad scope.
Building a Functionalizable, Potent Chemiluminescent Agent: A Rational Design Study on 6,8-Substituted Luminol Derivatives.
2021
Luminol is a prominent chemiluminescent (CL) agent, finding applications across numerous fields, including forensics, immunoassays, and imaging. Different substitution patterns on the aromatic ring can enhance or decrease its CL efficiency. We herein report a systematic study on the synthesis and photophysics of all possible 6,8-disubstituted luminol derivatives bearing H, Ph, and/or Me substituents. Their CL responses are monitored at three pH values (8, 10, and 12), thus revealing the architecture with the optimum CL efficiency. The most efficient pattern is used for the synthesis of a strongly CL luminol derivative, bearing a functional group for further, straightforward derivatization. …
Stereoselective cathodic synthesis of 8-substituted (1R,3R,4S)-menthylamines.
2015
The electrochemical generation of menthylamines from the corresponding menthone oximes equipped with an additional substituent in position 8 is described. Due to 1,3-diaxial interactions a pronounced diastereoselectivity for the menthylamines is found.
Synthesis of New 8-Arylisoquinoline Derivatives by Application of Palladium-Catalyzed Suzuki Cross-Coupling Reactions.
2005
Abstract New 8-(het)aryltetrahydroisoquinolines ( 10–14 ), 8-aryltetrahydroisoquinolin-4-ols ( 15 , 16 ), and 8-phenylisoquinolin-4-ol ( 17 ), flexible analogues of aporphine, were synthesized in good yields using palladium-catalyzed Suzuki cross-coupling reactions from 8-bromotetrahydroisoquinolin-4-one ( 6 ) as a common intermediate. We also describe the synthesis of this novel intermediate through an easy and efficient method, which involved intramolecular Friedel–Crafts cyclization.