ABSTRACT
The MoSGrid portal offers an approach to carry out high-quality molecular simulations on distributed compute infrastructures to scientists with all kinds of background and experience levels. A user-friendly Web interface guarantees the ease-of-use of modern chemical simulation applications well established in the field. The usage of well-defined workflows annotated with metadata largely improves the reproducibility of simulations in the sense of good lab practice. The MoSGrid science gateway supports applications in the domains quantum chemistry (QC), molecular dynamics (MD), and docking. This paper presents the open-source MoSGrid architecture as well as lessons learned from its design.
ABSTRACT
Phthalimides 1-6 undergo photochemical reactions upon direct irradiation as well as triplet sensitization and give rise to new products. Besides formation of the primary photoproducts, the first photochemical step initiates a subsequent thermal domino reaction or a domino sequence of a thermal and a photochemical reaction. The latter, involving two photochemical intramolecular gamma-H abstractions, was observed with phthalimides 1, 3, and 6 and delivered stereospecifically the hexacyclic benzazepine products 12, 19, and 27, respectively. The lowest triplet states of 1-6 were characterized in several solvents upon direct and acetone-sensitized excitation. The intermolecular electron transfer from triethylamine and DABCO was studied, and the radical anions were observed. Electrochemical measurements showed that intramolecular electron transfer from the adamantyl group of 1-6 to the lowest triplet state of the phthalimides is not feasible. The formation of products can be explained by intramolecular H-abstraction from the (alkyl)adamantane to the excited phthalimide, either from the excited singlet state or a hidden upper excited triplet state.
Subject(s)
Photochemistry , Phthalimides/chemistry , Electrochemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry , Spectrophotometry, Infrared , Spectrophotometry, UltravioletABSTRACT
The application of photoinduced electron transfer (PET) for the construction of heterocyclic ring systems is an appealing route in synthetic organic photochemistry. Electronically excited carbonyl chromophors in ketones, aldehydes, amides, or imides are strong electron acceptors that oxidize alkenes, amines, thioethers, or carboxylates. In subsequent steps, the radical anions formed thereof either are operating as secondary electron donors and initiate a photon-driven chain reaction or combine with electrophilic species and form products. These reactions are applied in the synthesis of heterocyclic compounds. The basic structures of these target molecules are bicyclic tertiary amines from the pyrrolizidine, benzopyrrolizidine, and indolizidine families, cyclic oligopeptides, macrocyclic ring systems, and many more.
Subject(s)
Biological Products/chemical synthesis , Heterocyclic Compounds/chemical synthesis , Photochemistry , Photons , Aldehydes/chemistry , Alkenes/chemistry , Amides/chemistry , Amines/chemistry , Carboxylic Acids/chemistry , Electron Transport , Free Radicals , Imides/chemistry , Indolizines/chemistry , Ketones/chemistry , Models, Chemical , Oxidation-Reduction , Peptides, Cyclic/chemistry , Pyrrolizidine Alkaloids/chemistry , Spectrophotometry, Ultraviolet , Sulfides/chemistryABSTRACT
The photodecarboxylative benzylation of N-alkyl, N-arylalkyl, and N-aryl phthalimides with arylacetic acids in aqueous solution proceeds via electron transfer from the arylalkanoate to the excited triplet state of the phthalimide, either formed directly or upon sensitization with acetone. The rate constant for triplet quenching of N-methylphthalimide is k(q) < 10(7) M(-1) s(-1) for 2-phenylacetic acid and k(q) = (1-3) x 10(9) M(-1) s(-1) for its mono-, di- and trimethoxy-substituted derivatives, suggesting a change of the mechanism for the primary oxidation step from a Photo-Kolbe type reaction yielding an acyloxy radical to a pseudo-Photo-Kolbe process involving the formation of resonance-stabilized zwitterion radicals as intermediates.
