Flavin–iodine coupled organocatalysis for the aerobic oxidative direct sulfenylation of indoles with thiols under mild conditions
作者:Ryoma Ohkado、Tatsuro Ishikawa、Hiroki Iida
DOI:10.1039/c8gc00117k
日期:——
A unique coupled redox organocatalysis system using flavin and iodine catalysts efficiently promoted the metal-free aerobic oxidative direct sulfenylation of indoles with thiols at ambient temperature without any sacrificial reagents, except environmentally benign molecular oxygen. Biomimetic flavin catalysis plays multiple roles in aerobic oxidative transformations, not only regenerating I2 from in
properties, and their catalytic activity in H2O2oxidations of sulfide, tertiary amine, and cyclobutanone. Reflecting the difference between the π-conjugated ring structures, the flavinium salts displayed very different redox properties, with reduction potentials in the order of: 5-ethylisoalloxazinium > 5-ethylalloxazinium > 1,10-ethylene-bridged alloxazinium. A comparison of their catalytic activity revealed
从市场上可买到的核黄素制备了一系列黄酮盐,5-乙基异all杂嗪鎓,5-乙基ethyl杂嗪鎓和1,10-乙烯桥联的四氧嘧啶鎓三氟甲磺酸盐。这项研究提出了它们的光学和氧化还原特性,以及它们在H 2 O 2中的催化活性之间的比较。硫化物,叔胺和环丁酮的氧化。反映了π-共轭环结构之间的差异,黄酮盐显示出非常不同的氧化还原性质,其还原电位的顺序为:5-乙基异四氮杂鎓> 5-乙基四氧杂鎓> 1,10-乙烯桥联的四氧杂嗪鎓。比较它们的催化活性表明,三氟甲磺酸5-乙基异恶唑嗪能特异性氧化硫化物和环丁酮,而三氟甲磺酸5-乙基异恶唑嗪能平稳地氧化叔胺。1,10-桥联的三氟甲磺酸铝恶唑鎓盐,可以很容易地从核黄素中大量获得,对硫化物和环丁酮的H 2 O 2氧化表现出中等的催化活性。
Synthesis of Riboflavines, Quinoxalinones and Benzodiazepines through Chemoselective Flow Based Hydrogenations
Robust chemical routes towards valuable bioactive entities such as riboflavines, quinoxalinones and benzodiazepines are described. These make use of modern flow hydrogenation protocols enabling the chemoselective reduction of nitro group containing building blocks in order to rapidly generate the desired amine intermediates in situ. In order to exploit the benefits of continuous processing the individual steps were transformed into a telescoped flow process delivering selected benzodiazepine products on scales of 50 mmol and 120 mmol respectively.
The mechanochemical N-alkylation of imide derivatives was studied. Reactions undersolvent-freeconditions in a ball mill gave good yields and could be put in place of the classical solution conditions. The method is general and can be applied to various imides and alkyl halides. Phthalimides prepared under ball milling conditions were used in a mechanochemical Gabriel synthesis of amines by their
Turning a riboflavin-binding protein into a self-sufficient monooxygenase by cofactor redesign
作者:Gonzalo de Gonzalo、Christian Smit、Jianfeng Jin、Adriaan J. Minnaard、Marco W. Fraaije
DOI:10.1039/c1cc14039f
日期:——
By cofactor redesign, self-sufficient monooxygenases could be prepared. Tight binding of N-alkylated flavins to riboflavin-binding protein results in the creation of artificial flavoenzymes capable of H2O2-driven enantioselective sulfoxidations. By altering the flavin structure, opposite enantioselectivities could be achieved, in accordance with the binding mode predicted by in silicoflavin-protein docking of the unnatural flavin cofactors. The study shows that cofactor redesign is a viable approach to create artificial flavoenzymes with unprecedented activities.