A safe, convenient, and regioselective synthesis of 3-halo coumarins using a metal halide (CuX2 alone or with ZnX2) promoted halogenation with N-halosuccinimide (NXS) as halide source is reported. The synthesis involved the steady in situ generation of highly reactive positive halogen (X+) by the coordination of copper or zinc with the N-halosuccinimide and subsequent electrophilic aromatic substitution
Electrochemical chlorination and bromination of electron-deficient C H bonds in quinones, coumarins, quinoxalines and 1,3-diketones
作者:Dan Yu、Ruixue Ji、Zhihui Sun、Wenjie Li、Zhong-Quan Liu
DOI:10.1016/j.tetlet.2021.153514
日期:2021.12
The electrochemistry-promoted chlorination and bromination of electron-deficient CH bonds was developed, using quinones, coumarins, quinoxalines and 1,3-diketones. This protocol features readily available and safe halogen sources (hydrochloric acid and KBr), high site-selectivity and mild reaction conditions. It could provide an efficient access to a series of chlorinated and brominated quinones, coumarins
Halogenated ketenes. 39. A new synthesis for substituted coumarins
作者:William T. Brady、C. H. Shieh
DOI:10.1002/jhet.5570210518
日期:1984.9
A new general synthesis of substituted coumarins is described. The in situ cycloaddition of chloroketenes with α-methoxymethylenecyclohexanones yields (4 + 2) cycloaddition products, 3,4-dihydro-2-pyranones. The chlorine atom is reductively removed and methanol is spontaneously eliminated to yield the 5,6,7,8-tetra-hydrocoumarins. Dehydrogenation of these compounds results in good yields of the substituted