[2 + 2 + 1] Heteroannulation of Alkenes with Enynyl Benziodoxolones and Silver Nitrite Involving C≡C bond Oxidative Cleavage: Entry to 3-Aryl-Δ<sup>2</sup>-isoxazolines
作者:Cheng-Yong Wang、Fan Teng、Yang Li、Jin-Heng Li
DOI:10.1021/acs.orglett.0c01285
日期:2020.6.5
A copper-catalyzed [2 + 2 + 1] heteroannulation of alkenes with enynyl benziodoxolones and AgNO2 involving oxidative cleavage of the C≡C bond promoted by cooperative Zn(OTf)2, KOAc, and 4 Å MS for producing 3-aryl Δ2-isoxazolines is reported. Mechanistic studies indicate that AgNO2 serves as the N/O two-atom unit source, enabling the formation of three bonds through NO2 addition across the C≡C bond
Catalyst Control in Positional-Selective C–H Alkenylation of Isoxazoles and a Ruthenium-Mediated Assembly of Trisubstituted Pyrroles
作者:Pravin Kumar、Manmohan Kapur
DOI:10.1021/acs.orglett.9b00446
日期:2019.4.5
determining the positional selectivity in C–H alkenylation of isoxazoles. A cationic rhodium-mediated, strong-directing group promotes C(sp2)-H activation at the proximal aryl ring whereas, the palladium-mediated electrophilic metallation leads to the C(sp2)-H activation at the distal position of the directing group. Synthetic elaboration of this C–H alkenylation product via ruthenium and copper co-catalysis
Unusual Reactivity of 4-Vinyl Isoxazoles in the Copper-Mediated Synthesis of Pyridines, Employing DMSO as a One-Carbon Surrogate
作者:Pravin Kumar、Manmohan Kapur
DOI:10.1021/acs.orglett.0c01935
日期:2020.8.7
An efficient protocol for the synthesis of nicotinate derivatives and tetrasubstituted pyridines through a copper-mediated cleavage of isoxazoles has been developed. The highlight of the work is the observation of an unusualreactivity of 4-vinyl isoxazoles under the reaction conditions. DMSO serves as a one-carbon surrogate generating an active methylene group during the reaction to form two C–C bonds