Unexpectedly Simple Synthesis of Benzazoles by<i>t</i>BuONa-Catalyzed Direct Aerobic Oxidative Cyclocondensation of<i>o-</i>Thio/Hydroxy/Aminoanilines with Alcohols under Air
tBuONa‐catalyzed directaerobicoxidativecyclocondensation reactions of readily available alcohols and o‐thio/hydroxy/aminoanilinesunderair have been developed and provide an efficient, practical, and green method for the synthesis of benzazoles. Mechanistic studies revealed that o‐substituted anilines promote the initial aerobicalcohol‐oxidation step, which explains the high reactivity and success
Benzoxazoles, benzothiazoles and benzimidazoles having substituents on the azole and benzene nuclei were synthesized evaluated for antifungal, insecticidal and herbicidal activities. It was found that benzimidazoles tended to exhibit antifungal activity while benzothiazoles tended to show herbicidal activity. Chloro, trifluoromethyl, methoxy and ethoxy groups at the 5 position were potent substituents, and the 2-pyridyl group at the 2 position is a common structural unit. Among several active derivatives, 7-chloro-2-(2-pyridyl) benzimidazole and 2-(2-pyridyl)-5-trifluoromethylbenzothiazole exhibited significant activity against Panonycus citri.
Synthesis of Benzothiazoles through Copper-Catalyzed One-Pot Three-Component Reactions with Use of Sodium Hydrosulfide as a Sulfur Surrogate
作者:Namjin Park、Yumi Heo、Manian Rajesh Kumar、Yong Kim、Kwang Ho Song、Sunwoo Lee
DOI:10.1002/ejoc.201101773
日期:2012.4
Copper-catalyzed one-pot three-component reactions of 2-iodoanilines, aldehydes, and NaSH·n H2O afford benzothiazoles in good yields. When CuCl was employed as a catalyst in the absence of a ligand, a variety of aromatic aldehydes and substituted 2-iodoanilines reacted with NaSH·n H2O to produce the corresponding 2-arylbenzothiazoles in 70–98 % yields. The copper catalyst plays a key role in C–S bond
Studies on organosulfur compounds. XI. Selective cyclization to benzothiazole by the reaction between quinaldine and meta-substituted anilines (or nitro compounds) under the modified Willgerodt-Kindler reaction.
作者:TAKUZO HISANO、MASATAKA ICHIKAWA
DOI:10.1248/cpb.22.2051
日期:——
In order to clarify in more detail the cyclization mechanism of thioanilides to benzothiazoles under the modified Willgerodt-Kindler reaction condition, quinaldine (I) was heated with meta-substituted anilines (II) or meta-substituted nitrobenzenes (III) in the presence of sulfur. Further, in order to examine on solvent effects through these processes, dimethylformamide (DMF) was employed. Although the yields of these reactions were different, the reactions also gave similarly thioanilides and one of the two possible benzothiazoles. The latter was proved to have the structure of 5-substituted 2-(2-quinolyl) benzothiazoles (V) by independent synthesis. On the other hand, the expected two isomeric benzothiazoles (V and VI) were obtained from the oxidaitve cyclization of thioanilides (IV) by the modified Jacobson reaction. Moreover, the thioanilides obtained from I or 2-picoline were found to react with the corresponding II in the presence of sulfur in DMF at 160-170°to give the selective cyclization product, respectively.
为了更详细地阐明硫代苯胺在改良的 Willgerodt-Kindler 反应条件下生成苯并噻唑的环化机理,在硫存在的情况下,将喹哪啶(I)与元取代苯胺(II)或元取代硝基苯(III)一起加热。此外,为了通过这些过程研究溶剂的影响,还使用了二甲基甲酰胺(DMF)。虽然这些反应的产率不同,但都得到了类似的硫代苯胺和两种可能的苯并噻唑中的一种。通过独立合成,证明后者具有 5-取代的 2-(2-喹啉基)苯并噻唑(V)的结构。另一方面,通过改进的雅各布森反应,硫代苯胺(IV)氧化环化得到了预期的两种异构体苯并噻唑(V 和 VI)。此外,还发现由 I 或 2-甲基吡啶得到的硫代苯胺与相应的 II 在 DMF 中于 160-170° 硫存在下发生反应,分别得到选择性环化产物。
Hisano,T.; Yabuta,Y., Chemical and pharmaceutical bulletin, 1973, vol. 21, p. 511 - 517