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Experimental and Computational Studies on Stepwise [3+2]‐Cycloadditions of Diaryldiazomethanes with Electron‐Deficient Dimethyl ( E )‐ and ( Z )‐2,3‐Dicyanobutenedioates
Author(s) -
Mlostoń Grzegorz,
Celeda Małgorzata,
Jasiński Radomir,
Heimgartner Heinz
Publication year - 2019
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201800837
Subject(s) - chemistry , diazomethane , carbene , diazo , cycloaddition , trimethylsilyl , adduct , medicinal chemistry , steric effects , yield (engineering) , dimer , stereochemistry , photochemistry , organic chemistry , catalysis , materials science , metallurgy
Electron‐deficient dimethyl ( E )‐ and ( Z )‐2,3‐dicyanobutenedioates (dimethyl dicyanofumarate and dicyanomaleate, respectively) react with diaryldiazomethanes at room temperature under spontaneous evolution of N 2 . The type of the products strongly depends on the structure of the diazo compound. Whereas diphenyldiazomethane and its bis(4‐methoxy) derivative yield cyclopropanes, sterically crowded 5‐diazo‐5 H ‐dibenzo[ a , d ]cycloheptane derivatives afford either the dimer of the carbene formed via N 2 elimination or the adduct of the carbene onto the starting diazo compound. The course of the studied reactions is rationalized by stepwise mechanisms initiated by the formation of a C–N bond. A cascade of reactions leads to the corresponding cyclopropanes or to release of a carbene species. The formation of a pyrazole via [3+2]‐cycloaddition (32CA) is observed only in reactions with (trimethylsilyl)diazomethane, which behaves similar to the parent diazomethane. The proposed mechanisms were analyzed computationally using the DFT method.