a new desulfurative method for generating primary, secondary, and tertiary alkyl radicals through visible‐light photoredoxcatalysis. A process that involves the generation of N‐centered radicalsfrom sulfinamide intermediates, followed by subsequent fragmentation, is critical to forming the corresponding alkyl radical species. This strategy has been successfully applied to conjugate addition reactions
Remarkable dependence of the regioselectivity of free radical additions to 3-cinnamoyloxazolidin-2-ones on the stability of the intermediate adduct-radical, electrophilicity of the adding radicals and the conditions for their generation
作者:Vitali I. Tararov、Nikolai Yu. Kuznetzov、Vladimir I. Bakhmutov、Nikolai S. Ikonnikov、Yuri N. Bubnov、Victor N. Khrustalev、Tatiana F. Saveleva、Yuri N. Belokon
DOI:10.1039/a701154g
日期:——
nucleophilic radicals (Pri) are found to add at 80 °C to the CC bond of 3-(E)-cinnamoyl-4-phenyloxazolidin-2-one 1a and 3-(E)-cinnamoyl-4-benzyloxazolidin-2-one 1b predominantly at the α-position of the bond. While for the CCl3 radical no product of β-addition has been found, for the Pri radical such a path constitutes up to 40% of the whole process at 80 °C. An interplay between the stability of the intermediate
发现亲电子基团(CCl 3)和亲核基团(Pr i)在80°C时会添加到3-(E)-肉桂酰基-4-苯基恶唑烷-2--2-酮1a和3-(E)-肉桂酰基的C C键上-4-苄基恶唑烷丁-2-酮1b主要位于键的α-位置。对于CCl 3自由基,没有发现β加成的产物,而对于Pr i自由基,这种途径在80°C下占整个过程的40%。调用中间加合物基团的稳定性与进行加成的基团的亲电子性或亲核性之间的相互作用,以使观察合理化。在低温(–23°C)下添加Pr i 自由基成为主要过程(高达75%)。
Reactivity of benzylidene and alkylidenemalonates in radical addition mediated with dialkylzincs – An intriguing story
作者:Hugo Lingua、Nejib Dwadnia、Didier Siri、Michèle P. Bertrand、Laurence Feray
DOI:10.1016/j.tet.2018.11.029
日期:2018.12
Benzylidene- and alkylidenemalonates are extremely reactive radical acceptors in dialkylzinc-mediated radical additions. Theoreticalinvestigations showed that the multi-step radical-polar crossover process should be highly exothermic. Not only the addition of the alkyl radical to the complexed substrate is enthalpically favored but what is more, the homolytic substitution at the metal leading to a