21370-59-2Relevant articles and documents
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Yoshino,Manabe
, p. 2860 (1963)
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Comparative investigation of the regioselectivity in styrene and α-methylstyrene hydroalkoxycarbonylation as a function of palladium catalyst structure
Benedek, Csilla,Toroes, Szilard,Heil, Balint
, p. 85 - 93 (1999)
Catalytic pathways of the styrene and α-methyl-styrene hydroalkoxycarbonylation in the presence of Pd(PPh3)2Cl2 and Pd(PPh3)2Cl2/SnCl2 catalyst precursors have been suggested. As a method, deuterium labelling with EtOD has been applied and it resulted in mixtures of mono- and polydeuterated reaction products, detected and determined by NMR methods. Comparative elucidation of the mechanisms governing these systems does support the assumption that the hydrido route is operative. The different behaviour of the metal-alkyl intermediates accounts for the observed strong influence of catalyst and substrate structure on regioselectivity.
Cyclopropanations via Heme Carbenes: Basic Mechanism and Effects of Carbene Substituent, Protein Axial Ligand, and Porphyrin Substitution
Wei, Yang,Tinoco, Antonio,Steck, Viktoria,Fasan, Rudi,Zhang, Yong
, p. 1649 - 1662 (2018)
Catalytic carbene transfer to olefins is a useful approach to synthesize cyclopropanes, which are key structural motifs in many drugs and biologically active natural products. While catalytic methods for olefin cyclopropanation have largely relied on rare transition-metal-based catalysts, recent studies have demonstrated the promise and synthetic value of iron-based heme-containing proteins for promoting these reactions with excellent catalytic activity and selectivity. Despite this progress, the mechanism of iron-porphyrin and hemoprotein-catalyzed olefin cyclopropanation has remained largely unknown. Using a combination of quantum chemical calculations and experimental mechanistic analyses, the present study shows for the first time that the increasingly useful C-C functionalizations mediated by heme carbenes feature an FeII-based, nonradical, concerted nonsynchronous mechanism, with early transition state character. This mechanism differs from the FeIV-based, radical, stepwise mechanism of heme-dependent monooxygenases. Furthermore, the effects of the carbene substituent, metal coordinating axial ligand, and porphyrin substituent on the reactivity of the heme carbenes was systematically investigated, providing a basis for explaining experimental reactivity results and defining strategies for future catalyst development. Our results especially suggest the potential value of electron-deficient porphyrin ligands for increasing the electrophilicity and thus the reactivity of the heme carbene. Metal-free reactions were also studied to reveal temperature and carbene substituent effects on catalytic vs noncatalytic reactions. This study sheds new light into the mechanism of iron-porphyrin and hemoprotein-catalyzed cyclopropanation reactions and it is expected to facilitate future efforts toward sustainable carbene transfer catalysis using these systems.
Iron(ii)-catalyzed intermolecular aziridination of alkenes employing hydroxylamine derivatives as clean nitrene sources
Berhal, Farouk,Grimaud, Laurence,Kirby, Georgina,Prestat, Guillaume,Vitale, Maxime R.
supporting information, p. 9428 - 9432 (2021/12/09)
The iron-catalyzed intermolecular aziridination of alkenes with hydroxylamine derivatives is described. Using simple iron(ii) sources and readily available ligands, the formal (2 + 1) cycloaddition process proved to be efficient on both styrenes and aliphatic alkenes, providing access to a wide range of aziridines. In these particularly sustainable reaction conditions, yields up to 89% could be obtained, with a catalyst loading which could be lowered to 5 mol% when the reaction was performed on large scale. Preliminary mechanistic studies suggest that both concerted and stepwise pathways are operating in this transformation. This journal is
Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
Iakovenko, Roman,Hlavá?, Jan
supporting information, p. 440 - 446 (2021/01/28)
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
