1393641-92-3Relevant academic research and scientific papers
An efficient oxidative conversion of 2-aryl-2H-chromenes to the corresponding flavones by tert-butylhydroperoxide and copper bromide
Banerjee, Dipanwita,Kayal, Utpal,Maiti, Gourhari
supporting information, p. 1667 - 1671 (2016/04/04)
A simple and efficient method has been developed for the facile oxidation of chromenes to the corresponding flavones by tert-butylhydroperoxide (TBHP) in the presence of copper(II) bromide catalyst in toluene at 80 °C in a very short time. The reaction demonstrates excellent reactivity, functional group tolerance, and good to excellent yields without using conventional strong oxidizing agents.
Metalloradical approach to 2H -chromenes
Paul, Nanda D.,Mandal, Sutanuva,Otte, Matthias,Cui, Xin,Zhang, X. Peter,De Bruin, Bas
, p. 1090 - 1096 (2014/02/14)
Cobalt(III)-carbene radicals, generated through metalloradical activation of salicyl N-tosylhydrazones by cobalt(II) complexes of porphyrins, readily undergo radical addition to terminal alkynes to produce salicyl-vinyl radical intermediates. Subsequent hydrogen atom transfer (HAT) from the hydroxy group of the salicyl moiety to the vinyl radical leads to the formation of 2H-chromenes. The Co(II)-catalyzed process can tolerate various substitution patterns and produces the corresponding 2H-chromene products in good isolated yields. EPR spectroscopy and radical-trapping experiments with TEMPO are in agreement with the proposed radical mechanism. DFT calculations reveal the formation of the salicyl-vinyl radical intermediate by a metalloradical-mediated process. Unexpectedly, subsequent HAT from the hydroxy moiety to the vinyl radical leads to formation of an o-quinone methide intermediate, which dissociates spontaneously from the cobalt center and easily undergoes an endocyclic, sigmatropic ring-closing reaction to form the final 2H-chromene product.
