902835-95-4Relevant academic research and scientific papers
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.
Synthesis of 2H-chromenes and 1,2-dihydroquinolines from aryl aldehydes, amines, and alkenylboron compounds
Petasis, Nicos A.,Butkevich, Alexey N.
experimental part, p. 1747 - 1753 (2009/10/11)
The one-step reaction of salicylaldehydes with amines and alkenyl boronic acids or alkenyl trifluoroborates to form 2H-chromenes (2H-1-benzopyrans) has been investigated in more detail and new suitable conditions have been identified, including the use of
