N-Arylphenothiazines as strong donors for photoredox catalysis - pushing the frontiers of nucleophilic addition of alcohols to alkenes
N-Arylphenothiazines as strong donors for photoredox catalysis - pushing the frontiers of nucleophilic addition of alcohols to alkenes
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DOI：
10.3762/bjoc.15.5
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发表时间：
2019-01-04
影响因子：
2.7
通讯作者：
Wagenknecht, Hans-Achim
中科院分区：
文献类型：
--
作者：
Speck, Fabienne;Rombach, David;Wagenknecht, Hans-Achim
合成了一系列新的N-苯基吩噻嗪类化合物作为潜在的光氧化还原催化剂，拓宽了甲醇与苯乙烯的光氧化还原亲核加成反应的底物范围。这些N-苯基吩噻嗪的不同之处在于其苯基上的供电子和吸电子取代基，既包括sigma基团，也包括pi-型基，以调节它们的吸收和电化学特性。在所合成的化合物中，烷胺化的N-苯基吩噻嗪被认为是非常适合用于光催化氧化还原的化合物。这些N-苯基吩噻嗪的二烷氨基取代基使估计的激发态还原电势最高可达-3.0V(VsSCE)。这些高度还原的性质允许将甲醇添加到α-甲基苯乙烯中，作为此类反应的活性较低的底物。在没有添加剂的情况下，对反应条件进行了优化，使Markovnivkov类加成产物在光照20h后达到定量产率。
A new range of N-phenylphenothiazine derivatives was synthesized as potential photoredox catalysts to broaden the substrate scope for the nucleophilic addition of methanol to styrenes through photoredox catalysis. These N-phenylphenothiazines differ by their electron-donating and electron-withdrawing substituents at the phenyl group, covering both, sigma and pi-type groups, in order to modulate their absorbance and electrochemical characteristics. Among the synthesized compounds, alkylaminylated N-phenylphenothiazines were identified to be highly suitable for photoredox catalysis. The dialkylamino substituents of these N-phenylphenothiazines shift the estimated excited state reduction potential up to -3.0 V (vs SCE). These highly reducing properties allow the addition of methanol to alpha-methylstyrene as less-activated substrate for this type of reaction. Without the help of an additive, the reaction conditions were optimized to achieve a quantitative yield for the Markovnivkov-type addition product after 20 h of irradiation.