Oligosubstituted Pyrroles Directly from Substituted Methyl Isocyanides and Acetylenes

The formal cycloaddition of α‐metallated methyl isocyanides 1 onto the triple bond of electron‐deficient acetylenes 2 represents a direct and convenient approach to oligosubstituted pyrroles 3. The scope and limitations of this reaction (24 examples, 25–97 % yield) are reported along with an optimiz...

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Published in:Chemistry : a European journal 2009-01, Vol.15 (1), p.227-236
Main Authors: Lygin, Alexander V., Larionov, Oleg V., Korotkov, Vadim S., de Meijere, Armin
Format: Article
Language:English
Subjects:
Alkynes - chemistry
Catalysis
copper
Copper - chemistry
Cyanides - chemical synthesis
Cyanides - chemistry
cycloaddition
isocyanides
pyrroles
Pyrroles - chemical synthesis
Pyrroles - chemistry
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Summary:The formal cycloaddition of α‐metallated methyl isocyanides 1 onto the triple bond of electron‐deficient acetylenes 2 represents a direct and convenient approach to oligosubstituted pyrroles 3. The scope and limitations of this reaction (24 examples, 25–97 % yield) are reported along with an optimization of the reaction conditions and a rationalization of the mechanism. In addition, a related newly developed CuI‐mediated synthesis of 2,3‐disubstituted pyrroles by the reaction of copper acetylides derived from unactivated terminal alkynes with substituted methyl isocyanides is described (11 examples, 5–88 %yield). Convenient pyrrole syntheses: Two new protocols have been developed for one‐pot, one‐step formal [3+2] cycloadditions of substituted methyl isocyanides onto the triple bond of either acceptor‐activated internal or non‐activated terminal acetylenes leading to 2,3,4‐trisubstituted and 2,3‐disubstituted pyrroles, respectively (see scheme).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.200801395