106624-48-0Relevant academic research and scientific papers
Cycloaddition Behavior of 2-Substituted Norbornadienes towards 4-Phenyl-1H-1,2,4-triazole-3,5-dione (PTAD): Homo Diels-Alder Reactivity versus Insertion, Rearrangement, and Cycloaddition
Adam, Waldemar,Lucchi, Ottorino de,Pasquato, Lucia,Will, Bernd
, p. 531 - 536 (2007/10/02)
The reaction of PTAD with 2-trimethylsilyl-, 2-chloro-, 2-cyano-, and 2-methoxycarbonylnorbornadienes 1 a-d, respectively, was investigated.In all cases homo Diels-Alder adducts were obtained, for 1a the unexpected regioisomer, the 1-trimethylsilyl derivative 2a, and for other norbonadienes 1 b-d the usual cyclopropane-substituted products 2 b-d.Except for the trimethylsilyl sytem 1a, for which also the dicarboximides 4a and 4'a, respectively, (rearrangement urazoles) were obtained, the other norbornadienes 1b-d afforded the insertion products 5 b-d.With increasing electron-withdrawal by the 2-substituents the insertion products 5 b-d increased at the expense of the homo Diels-Alder adducts 2 b-d.These results are mechanistically rationalized in terms of stepwise cycloaddition via 1,5-dipolar intermediates.In the case of 2-chloronorbornadiene (1b), besides the homo Diels-Alder 2b, the rearrangement urazole 4b and the insertion product 5b, also the cycloadduct 3b was formed.
