Synthesis of Pyrroles through Coupling of Enyne-hydrazones with Fischer Carbene Complexes
摘要:
The coupling of enyne-imines with Fischer carbene complexes leads to the formation of alkenylpyrrole derivatives. Maximum yields of pyrrole adducts were obtained using N,N-dimethylhydrazones. A mechanism involving alkyne insertion followed by nucleophilic attack of the imine nitrogen at the intermediate alkenylcarbene complex was proposed.
A general and regioselective synthesis of substituted pyrroles 2 by cycloisomerization of readily available (Z)-(2-en-4-ynyl)amines 1 is reported. Spontaneous cycloisomerization leading to 2 occurred in the course of preparation of enynamines bearing a terminal triple bond or a triple bond substituted with a phenyl or a CH2OTHP group. When the triple bond was substituted with an alkyl or alkenyl group
Palladium-Catalyzed Alkoxycarbonylation of Conjugated Enyne Oxiranes: A Diastereoselective Method for the Synthesis of 7-Hydroxy-2,3,5-trienoates
作者:Melih Kuş、Levent Artok、Muhittin Aygün
DOI:10.1021/acs.joc.5b00382
日期:2015.6.5
Palladium-catalyzed alkoxycarbonylative 1,5-substitution of conjugatedenyne oxiranes provides a diastereoselective route to (E)-configured 7-hydroxy-2,3,5-trienoates. The reactions proceeded in a highly stereoselective manner, possibly through sequential formation of π-allylpalladium and σ-vinylallenyl palladium complexes. The major diastereomeric form of the product is determined by the configuration
Pd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.