7-O-取代-8-甲基香豆素和4H-色烯-4-酮化合物与NBS/CCl_4试剂的溴化反应

Bromination of 7-O-Substituted-8-methyl-coumarins and 4H-Chromen-4-ones with N-Bromosuccinimide in CCl_4

7-O-取代-8-甲基香豆素和4-H-色烯-4-酮化合物是合成Seco-DCK和Seco-DCP类似物的重要中间体.报道了在NBS/CCl4条件下,这两类化合物8-位甲基溴代反应的情况.通过实验发现,这两类化合物8-位甲基溴代反应较一般芳环苄位的溴代更为复杂,存在多个反应位点.影响8-位甲基溴代选择性和收率的主要因素有三:邻位基团空间位阻大小、自由基引发催化剂的使用与否以及邻位基团的电性因素.通过控制反应条件,可以中等收率得到8-位甲基溴代化合物.

The bromination of 7-O-substituted-8-methyl-coumarins and 4H-chromen-4-ones,two key in-termediates in the synthesis of Seco-DCK and Seco-DCP analogues,with N-bromosuccinimide in CCl4 is reported.The experimentation showed that the selectivity of bromination of 8-methyl is more complicated than that of common benzyls,due to the presence of multiple reactive sites in these two title substrates.Diversity of the products was discussed and the reasonable explanation for which was provided.The bulky group of 7-O-substitutes,its electric property as well as addition of free radical initiator could affect the selectivity and the yield of bromination of 8-methyl.The desired 8-bromomethyl products could be obtained in mild yields under optimized condition.