Flow microreactors have allowed an efficient extended Pummerer reaction of ketene dithioacetal monoxides with anilines by precise control of unstable sulfonium intermediates and spatial separation ...
Palladium-Catalyzed Zinc-Amide-Mediated CH Arylation of Fluoroarenes and Heteroarenes with Aryl Sulfides
作者:Shinya Otsuka、Hideki Yorimitsu、Atsuhiro Osuka
DOI:10.1002/chem.201502101
日期:2015.10.12
heteroarenes with aryl sulfides proceeds smoothly with the aid of a palladium–N‐heterocyclic carbene catalyst. A bulky zinc amide, TMPZnCl⋅LiCl, plays a key role as an effective base to generate the corresponding arylzinc species in situ. This arylation protocol is practically much easier to perform than our previous method, which necessitates preparation of the arylzincreagents in advance from the corresponding
Ç polyfluoroarenes和杂芳烃的与芳基硫化物ħ芳基化用钯- N-杂环卡宾催化剂的帮助下顺利进行。甲笨重锌酰胺,TMPZnCl ⋅的LiCl,起着以原位产生相应的芳基锌物种的有效碱关键作用。该芳基化方案实际上比我们以前的方法更容易执行,后者需要从相应的芳基卤化物预先制备芳基锌试剂。通过硫特异性反应(如S N Ar磺酰化反应和扩展的Pummerer反应)制备的芳基硫化物会经历这种直接芳基化,从而提供有趣的转化,而这些转化是传统的基于卤素的有机合成难以实现的。
Two-Step, Practical, and Diversity-Oriented Synthesis of Multisubstituted Benzofurans from Phenols through Pummerer Annulation Followed by Cross-coupling
作者:Kei Murakami、Hideki Yorimitsu、Atsuhiro Osuka
DOI:10.1246/bcsj.20140241
日期:2014.12.15
Practical and diversity-oriented synthesis of multisubstituted benzofurans has been accomplished from simple phenols through a Pummerer annulation/cross-coupling sequence. Operationally simple and rapid reactions of phenols with ketene dithioacetal monoxides (KDMs) with the aid of trifluoroacetic anhydride provide the corresponding 2-methylsulfanylbenzo[b]furans. The scope of the reaction encompasses phenols and KDMs having a broad range of substituents. The remaining methylsulfanyl group in the annulation products is converted to various aryl groups through cross-coupling reactions that we improved specially to this end. This two-step approach to multisubstituted benzofurans is powerful enough to synthesize highly fluorescent benzofuran derivatives as well as the naturally occurring Eupomatenoid family.
Copper-Catalyzed Extended Pummerer Reactions of Ketene Dithioacetal Monoxides with Alkynyl Sulfides and Ynamides with an Accompanying Oxygen Rearrangement
and ynamides provided a wide variety of γ,γ‐disulfanyl‐β,γ‐unsaturated carbonyl compounds with an accompanying oxygen rearrangement. The products can be easily converted into 1,4‐dicarbonyl compounds and substituted heteroaromatics. DFT calculations and mechanistic experiments revealed a new interesting stepwise addition/oxygen rearrangement mechanism.
synthesis of fluorinated benzofurans from polyfluorophenols has been accomplished by means of a sigmatropic dearomatization/defluorination strategy composed of three processes: (1) interrupted Pummerer reaction of ketene dithioacetal monoxides with polyfluorophenols followed by [3,3] sigmatropicrearrangement, (2) Zn‐mediated smooth reductive removal of fluoride from the dearomatized intermediate, and