Reactions of 1-aryl-2,2-dihalogenoethanone oximes with tetrasulfur tetranitride (S4N4): a general method for the synthesis of 3-aryl-4-halogeno-1,2,5-thiadiazoles
作者:Sung Cheol Yoon、Jaeeock Cho、Kyongtae Kim
DOI:10.1039/a704408i
日期:——
on the basis of 1H NMR spectroscopic evidence and an X-ray crystallographic analysis of 1-(3-chlorophenyl)-2,2-dichloroethanone oxime 7f. The 1-aryl-2,2-dihalogenoethanone oximes react with tetrasulfurtetranitride in refluxing 1,4-dioxane to give 3-aryl-4-chloro-1, 3-aryl-4-bromo-2, and 3-aryl-4-fluoro-1,2,5-thiadiazoles 3 in 69–98, 49–99, and 32–65% yields, respectively. A mechanism for the formation
1-芳基-2,2-二氯-7、1-芳基-2,2-二溴-8、1-芳基-2-溴-2-氟-9和1-芳基-2-氯-2-氟-通过在室温下在EtOH中使相应的酮与盐酸羟胺反应来制备乙酮肟10。在1 H NMR光谱证据和1-(3-氯苯基)-2,2-二氯乙酮肟7f的X射线晶体学分析的基础上,对肟进行立体化学分配。1-芳基-2,2-二卤代乙酮肟与四氮化四硫反应,回流1,4-二恶烷,得到3-芳基-4-氯-1、3-芳基-4-溴-2和3-芳基-4 -氟-1,2,5-噻二唑3的产率分别为69-98、49-99和32-65%。提出了形成1,2,5-噻二唑的机理。
Electrocatalytic synthesis of α,α-<i>gem</i>-dihalide ketones from α-mono-halide ketones and unexpected dimer condensation
However, when the aqueous solution contained NaOH, two α-mono-halide ketone molecules had a special dimer condensation. The reaction mechanisms were explored by conducting GC-MS, EPR, and CV with DFT calculations. These revealed that in situ generation of a halogen radical initiated electrocatalytic halogenation, while the dimer condensation involved a hydroxyl radical-mediated C1 fragment elimination.
The development of highly enantio- and c organocatalytic monofluorovinylations is presented. Based on the application of alpha-fluoro beta-keto-benzothiazolesulfones, the formal addition of a monofluorovinylic anion synthon to a range of acydic and cyclic enones, as well as imines, is shown. These procedures give selective access to both E- and Z-isomers of the monofluorovinylated products, which are isolated as the pure diastereoisomers in good to excellent yields with up to 99% ee. Furthermore, the application of this concept for the formation of highly enantioenriched bicylic compounds containing a monofluorovinyl moiety is also described. In addition, a mechanistic rationale for the observed E:Z-selectivities is presented.