Rh(III)-Catalyzed C–H Activation/Cyclization of Benzamides and Diazonaphthalen-2(1<i>H</i>)-ones for Synthesis of Lactones
作者:Renjie Chen、Sunliang Cui
DOI:10.1021/acs.orglett.7b01728
日期:2017.8.4
A Rh(III)-catalyzed C–Hactivation/cyclization of benzamides and diazonaphthalen-2(1H)-ones for synthesis of lactones has been developed. In the presence of Rh(III) catalysis, the benzamides would form rhodacycle species and could be trapped by diazonaphthalen-2(1H)-ones for arylation, and the following intramolecular lactonization would rapidly furnish the products. Thus, the diazonaphthalen-2(1H)-ones
Facile synthesis of coumarin via the tandem reaction of salicylaldehyde with aryl-substituted 1,1-dibromo-1-alkene was developed. This new protocol proceeds smoothly under mild and transition-metal-free conditions, it allows rapid access to coumarins containing various heteroatoms that are more difficult to prepare by traditional methods. Based on the isolated intermediate of 4-(diethylamino)-3-phenylchroman-2-one and detailed mechanistic studies, a credible tandem pathway was proposed.
作者:Tamal Roy、Myungjo J. Kim、Yang Yang、Suyeon Kim、Gyumin Kang、Xinyi Ren、Anders Kadziola、Hee-Yoon Lee、Mu-Hyun Baik、Ji-Woong Lee
DOI:10.1021/acscatal.9b01087
日期:2019.7.5
We report a Michael-type cyanation reaction of coumarins by using CO2 as a catalyst. The delivery of the nucleophilic cyanide was realized by catalytic amounts of CO2, which forms cyanoformate and bicarbonate in the presence of water. Under ambient conditions, CO2-catalyzed reactions afforded high chemo- and diastereoselectivity of beta-nitrile carbonyls, whereas only low reactivities were observed under argon or N-2. Computational and experimental data suggest the catalytic role of CO2, which functions as a Lewis acid, and a protecting group to mask the reactivity of the product, suppressing byproducts and polymerization. The utility of this convenient method was demonstrated by preparing biologically relevant heterocyclic compounds with ease.
PHANSALKAR, MAHESH S.;DESHMUKH, KESHAV K.;KELKAR, SHRINIWAS L.;WADIA, MUR+, INDIAN J. CHEM., 26,(1987) N 6, 562-563