Reductive Couplings of 2-Halopyridines without External Ligand: Phosphine-Free Nickel-Catalyzed Synthesis of Symmetrical and Unsymmetrical 2,2′-Bipyridines
摘要:
An unexpectedly facile synthetic approach for symmetrical and unsymmetrical 2,2'-bipyridines through the Ni-catalyzed reductive couplings of 2-halopyridines was developed. The couplings were efficiently catalyzed by 5 mol % of NiCl2 center dot 6H(2)O without the use of external ligands. A variety of 2,2'-bipyridines including caerulomycin F have been efficiently synthesized.
Generation and Reactions of Pyridyllithiums via Br/Li Exchange Reactions Using Continuous Flow Microreactor Systems
作者:Aiichiro Nagaki、Daisuke Yamada、Shigeyuki Yamada、Masatomo Doi、Daisuke Ichinari、Yutaka Tomida、Naofumi Takabayashi、Jun-ichi Yoshida
DOI:10.1071/ch12440
日期:——
A continuous flowmicroreactor method for generating and carrying out reactions on pyridyllithiums has been developed based on Br/Li exchange reactions of bromopyridines and dibromopyridines. The reactions can be carried out without using cryogenic conditions by virtue of short residence times and efficient heat transfer, while very low temperatures such as –78 or –110°C are required for conventional
Flow microreactor synthesis of disubstituted pyridines from dibromopyridines via Br/Li exchange without using cryogenic conditions
作者:Aiichiro Nagaki、Shigeyuki Yamada、Masatomo Doi、Yutaka Tomida、Naofumi Takabayashi、Jun-ichi Yoshida
DOI:10.1039/c0gc00852d
日期:——
A flow microreactor method for the synthesis of disubstituted pyridines by generation of pyridyllithiums followed by reactions with electrophiles has been developed. By using a short residence time and efficient temperature control, the cryogenic conditions required for conventional batch macro processes can be avoided. Sequential introduction of two different electrophiles into dibromopyridines has
Pyridyltellurium derivatives have been prepared from the reaction of halopyridines with lithium butanetellurolate and the tellurium–metal exchange of pyridyltellurium derivatives has been investigated using butyllithium and dilithium dimethylcyanocuprate.
corresponding pyridylmagnesium chlorides at room temperature by treatment with iPrMgCl. The resulting Grignard reagents were quenched by various electrophiles to afford functionalized pyridines. The brominemagnesium exchange of some dibromopyridines was also studied.
Bromine–magnesium exchange using iPrMgCl in THF at roomtemperature on 2-, 3- and 4-bromopyridines allowed the synthesis of various functionalized pyridines. The methodology was successfully used for the synthesis of 4-azaxanthone. Moreover, single exchange reactions observed on 2,6-, 3,5-, 2,3- and 2,5-dibromopyridines, with complete regioselectivity in the case of 2,3- and 2,5-dibromopyridines, afforded