Rhodium-Catalyzed Site-Selective Coupling of Indoles with Diazo Esters: C4-Alkylation versus C2-Annulation
作者:Xiaohong Chen、Guangfan Zheng、Yunyun Li、Guoyong Song、Xingwei Li
DOI:10.1021/acs.orglett.7b03099
日期:2017.11.17
A Rh(III)-catalyzed site-selective C–H activation of C(3)-functionalized indoles in a coupling with diazo esters has been realized with carbonyl as a weakly coordinating group. The coupling selectivity is dictated by the temperature and additives, affording either C4-alkylated indoles or C2-annulated lactones in moderate to excellent efficiency.
作者:Banjare, Shyam Kumar、Afreen, Saista、Kong, Wang-Yeuk、Guo, Wentao、Nanda, Tanmayee、Das Adhikari, Gopal Krushna、Preeyanka, Naupada、Tantillo, Dean J.、Ravikumar, Ponneri C.
DOI:10.1021/acs.joc.3c01845
日期:——
A Simple, Effective, Green Method for the Regioselective 3-Acylation of Unprotected Indoles
作者:Phuong Tran、Hai Tran、Poul Hansen、Mai Do、Thach Le
DOI:10.3390/molecules201019605
日期:——
A fast and green method is developed for regioselective acylation of indoles in the 3-position without the need for protection of the NH position. The method is based on Friedel-Crafts acylation using acid anhydrides. The method has been optimized, and Y(OTf)3 in catalytic amounts is found to be the best catalyst together with the commercially available ionic liquid [BMI]BF4 (1-butyl-3-methylimidazolium tetrafluoro-borate) as solvent. The reaction is completed in a very short time using monomode microwave irradiation. The catalyst can be reused up to four times without significant loss of activity. A range of substituted indoles are investigated as substrates, and thirteen new compounds have been synthesized.
coordination facilitated tunable reactivity between alkenylation and alkylation of indoles at the C4 C-H site is presented using readily accessible allylic alcohols in the presence of Rh catalysis by switching the additives or directing group. Exclusive site selectivity, functional group tolerance, and late-stage modifications are the important practical features.