1646-67-9Relevant articles and documents
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Ranganathan,Kar
, p. 1855,1857 (1971)
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Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via TiII/TiIV redox catalysis
Gilbert, Zachary W.,Hue, Ryan J.,Tonks, Ian A.
, p. 63 - 68 (2015/12/30)
Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally TiII/TiIV redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a TiII species. The key component for catalytic turnover is the reoxidation of the TiII species to a TiIV imido via the disproportionation of an η2-diazene-TiII complex.
Palladium-catalyzed reaction of arylamine and diarylacetylene: Solvent-controlled construction of 2,3-diarylindoles and pentaarylpyrroles
Chen, Xiaopeng,Li, Xihui,Wang, Ningning,Jin, Jisong,Lu, Ping,Wang, Yanguang
scheme or table, p. 4380 - 4386 (2012/09/21)
By choosing DMF and dioxane as solvent, skeletons of indoles and pyrroles were constructed from alkynes and amines in the presence of PdCl2, respectively. These Pd-catalyzed reactions were phosphane-free with high atom efficiency and could be conducted under mild basic conditions. The proposed mechanism for the selective formation of indoles and pyrroles in different solvents is also discussed in this paper. Two different kinds of Pd-catalyzed cyclizations, leading to the construction of 2,3-diarylindole and pentaarylpyrrole from the same alkyne and aniline starting materials, were approached by choosing different solvents. The mechanisms for these solvent-controlled reactions are proposed and discussed. Copyright