Stereoselective synthesis of dihydrothiadiazinoazines and dihydrothiadiazinoazoles and their pyrolytic desulfurization ring contraction
作者:Alya Al-Etaibi、Elizabeth John、Maher R. Ibrahim、Nouria A. Al-Awadi、Yehia A. Ibrahim
DOI:10.1016/j.tet.2011.06.034
日期:2011.8
4]thiadiazines isomerize also in DMSO-d6 into the corresponding cis-stereoisomers. Pyrolytic conversion of these heterocyclic condensed dihydrothiadiazines into their corresponding pyrazolo[5,1-b][1,2,4]triazoles, pyrazolo[5,1-c][1,2,4]triazin-4-ones and pyrazolo[4,3-b]quinazolin-9-ones via desulfurization ring contraction is described.
分子内碱催化的C–C键形成导致反式-6,7-dihydro-5 H- [1,2,4]三唑[3,4- b ] [1,3,4]噻二嗪,反式的排他立体选择性合成-7,8-二氢-6- ħ - [1,2,4]三嗪并[3,4- b ] [1,3,4]噻二嗪-4-酮,和反式-3,4-二氢2 ħ - [1,3,4] thiadiazino [2,3 - b ] quinazolin-10-one。反式-6,7-二氢-5- ħ - [1,2,4]三唑并[3,4- b ] [1,3,4]噻二嗪在CDCl慢慢异构化3和更迅速地在DMSO- d 6为相应的顺式立体异构体。另一个反式-6,7-二氢-[1,3,4]噻二嗪在DMSO- d 6中也异构化为相应的顺式立体异构体。这些杂环缩合的二氢噻二嗪热解转化为其相应的吡唑并[5,1- b ] [1,2,4]三唑,吡唑并[5,1- c ] [1,2,4]三嗪-4-酮和吡唑并[描述了通过脱硫环收缩的4,3