photocatalytic aerobicoxidative lactonization of arene C(sp2)–H bonds proceeds in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tert-butyl nitrite (TBN). Under the optimized conditions, a range of 2-arylbenzoic acids is converted into the corresponding benzocoumarin derivatives in moderate to excellent yields. This method is characterized by its atom economy, mild reaction conditions, the
Cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids
作者:Ketan Wadekar、Suraj Aswale、Veera Reddy Yatham
DOI:10.1039/c9ob02676b
日期:——
The first cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids has been developed. This operationally simple protocol allows rapid access to synthetically useful coumarins on gram scale by employing CeCl3 as a photocatalyst and O2 as a terminal oxidant. Overall, this delivers an economical and environmentally amiable entry to diversely substituted coumarins, important structural
A practical, electrochemical method is developed for the direct dehydrogenative lactonization of C(sp2/sp3)–H bonds under external oxidant- and metal-free conditions, delivering diverse lactones, including coumarin derivatives with excellent regioselectivity. The scalable nature of this newly developed electrochemical process was demonstrated on a 40 g scale following an operationally simple protocol
<i>tert</i>-Butyl Nitrite-Mediated Synthesis of <i>N</i>-Nitrosoamides, Carboxylic Acids, Benzocoumarins, and Isocoumarins from Amides
作者:Subhash L. Yedage、Bhalchandra M. Bhanage
DOI:10.1021/acs.joc.7b00570
日期:2017.6.2
(TBN) as a multitask reagent for (1) the controlled synthesis of N-nitrosoamide from N-alkyl amides, (2) hydrolysis of N-methoxyamides to carboxylic acids, (3) metal- and oxidant-free benzocoumarin synthesisfrom ortho-aryl-N-methoxyamides via N–H, C–N, and C–H bond activation, and (4) isocoumarin synthesisusingRu(II)/PEG as a recyclable catalytic system via ortho-C–H activation and TBN as an oxygen source