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One‐Pot Selective Syntheses of 5‐Azaindoles through Zirconocene‐Mediated Multicomponent Reactions with Three Different Nitrile Components and One Alkyne Component
Author(s) -
Zhang Shaoguang,
Zhang WenXiong,
Zhao Jing,
Xi Zhenfeng
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201003119
Subject(s) - regioselectivity , chemistry , ring (chemistry) , nitrile , alkyne , stereochemistry , group 2 organometallic chemistry , component (thermodynamics) , combinatorial chemistry , organic chemistry , molecule , catalysis , physics , thermodynamics
5‐Azaindoles either with three different substituents at their 2‐, 4‐, and 6‐positions or with two identical substituents at their 2‐ and 6‐positions and a different one at the 4‐position, were obtained in good to excellent isolated yields by a zirconocene‐mediated multicomponent process. Each reaction involved four organic partners, comprising a Si‐tethered diyne, one t BuCN component, and two (either different or identical) nitriles. All these four components were combined through the action of a Cp 2 Zr II species into a three‐ring fused Zr/Si‐containing organometallic complex in a perfectly chemo‐ and regioselective manner. This multicomponent reaction process consisted of three reaction steps, all of which were made clear through the isolation and characterization of their corresponding organometallic intermediates: the zirconacyclopropene‐azasilacyclopentadienes 2 , the allenyl‐aza‐zirconacycles 3 , and the three‐ring fused complexes 6 . X‐ray single‐crystal structural analyses of two three‐ring fused Zr/Si‐containing intermediates and two 5‐azaindoles unambiguously showed the positions of the different substituents and the regioselectivity. Iminopyrrole derivatives could be also highly selectively prepared from a Si‐tethered diyne and two different nitriles.