Efficient Reagents for the Synthesis of 5-, 7-, and 5,7-Substituted Indoles Starting from Aromatic Amines: Scope and Limitations
摘要:
Upon reaction with IPy(2)BF(4), 4-substituted anilines give regioselectively the corresponding o-iodoanilines in nearly quantitative yield, in a process that can be carried out on a multigram scale. Palladium-catalyzed coupling of the resulting 2-iodoanilines with (trimethylsilyl)acetylene (TMSA), followed by efficient CuI-mediated nitrogen cyclization onto alkynes with concurrent elimination of the TMS substituent, allows a straightforward elaboration of 5-mono- and 5,7-disubstituted indoles from aromatic amines. This new approach to the aforementioned indoles does not requires protective groups on nitrogen at any step and can be adapted for preparing related 7-manosubstituted indoles. Moreover, examples iterating the process are given, allowing bis-annulation and sequential double annulation and resulting in synthesis of benzodipyrroles. Additionally, suitable conditions for iodination of some of the target indoles with IPy(2)BF(4) are discussed.
Efficient Reagents for the Synthesis of 5-, 7-, and 5,7-Substituted Indoles Starting from Aromatic Amines: Scope and Limitations
作者:Jesús Ezquerra、Concepción Pedregal、Carlos Lamas、José Barluenga、Marta Pérez、Miguel Angel García-Martín、José M. González
DOI:10.1021/jo952119+
日期:1996.1.1
Upon reaction with IPy(2)BF(4), 4-substituted anilines give regioselectively the corresponding o-iodoanilines in nearly quantitative yield, in a process that can be carried out on a multigram scale. Palladium-catalyzed coupling of the resulting 2-iodoanilines with (trimethylsilyl)acetylene (TMSA), followed by efficient CuI-mediated nitrogen cyclization onto alkynes with concurrent elimination of the TMS substituent, allows a straightforward elaboration of 5-mono- and 5,7-disubstituted indoles from aromatic amines. This new approach to the aforementioned indoles does not requires protective groups on nitrogen at any step and can be adapted for preparing related 7-manosubstituted indoles. Moreover, examples iterating the process are given, allowing bis-annulation and sequential double annulation and resulting in synthesis of benzodipyrroles. Additionally, suitable conditions for iodination of some of the target indoles with IPy(2)BF(4) are discussed.
Revisiting the Gold-Catalyzed Dimerization of 2-Ethynylanilines: A Room-Temperature and Silver-Free Protocol for the Synthesis of Multifunctional Quinolines
作者:Chandrasekar Praveen、P. Perumal
DOI:10.1055/s-0035-1561305
日期:——
heterocyles also as exemplified by the preparation of naphthyridines. Competition reactions to determine the reactivity of dissimilar alkynes demonstrated that the product ratio of dimerization vsintermolecular addition is rather dependent on the electronic nature of aryl substituent on the alkynes. However, control experiments with substrates possessing internal alkynes resulted in cycloisomerization