A highly efficient and environmentally benign synthesis of 6,8-dibromoflavones, 8-bromoflavones, 5,7-dibromoaurones and 7-bromoaurones
作者:Abu T. Khan、Papori Goswami
DOI:10.1016/j.tetlet.2005.05.102
日期:2005.7
Various ring substituted 6,8-dibromoflavones (3a-e) as well as 8-bromoflavolics (3f-j) can be synthesized easily from the corresponding 2'-hydroxychalcones (1a-j) in good yields and in two steps under environmentally benign reaction conditions. This can be achieved by bromination with concomitant cyclization by using a combination of vanadium pentoxide, hydrogen peroxide and ammonium bromide in dichloromethane-water at 0-5 degrees C, followed by dehydrobromination of the brominated products 2a-j using 0.2 M ethanolic KOH Solution at ice-bath temperature. On the other hand, various 5,7-dibromoaurones and 7-bromoaurone derivatives 6a-c can be obtained, exclusively, from the corresponding 2'-acetoxychalcones (4a-c) in good yields and in two steps by turing the reaction conditions. (c) 2005 Elsevier Ltd. All rights reserved.
Oyamada, Justus Liebigs Annalen der Chemie, 1939, vol. 538, p. 44,52
作者:Oyamada
DOI:——
日期:——
Blom; Tambor, Chemische Berichte, 1905, vol. 38, p. 3590