Generally, if we look at the structure of furan and azo bond, they both act as diene and dienophile but some and only some authours had reported that furan group undergoes an electrophilic aromatic substitution reaction instead of Diels-Alder reaction. Can anyone explain me the reason? Kindly provide the references as well.
https://doi.org/10.1016/S0040-4039(00)93129-0
http://pubs.rsc.org/en/content/articlelanding/2013/cc/c3cc40588e#!divAbstract
Furan can act as a 4pi or 2pi component of the reaction depending of the conditions…
If you are looking for a normal hetero Diels-Alder i.e., electron rich diene – Homo controlled with an electron deficient dienofile – Lumo controlled the furan will act as 4pi. (there are plenty of literature examples)
If you are looking for an inverse electron demand reaction with an electron poor diene –Lumo controlled, and an electron rich dienofile (in this case Furan)-Homo controlled the furan will act as dienofile.
Some times what it looks like an alkylation can be an cycloaddition followed by ring opening due to rearomatization
See for example Gilchrist et all J. Chem. Soc. Perkin 1, 1983, 1283
Thanks for your answer. But the reaction what's given in the reference, can you answer why such thing is happening? Why insted of conventional DA reaction, such electrophilic aromatic substitutino reaction is happening?
You can search the SciFinder and then you will see many articles and how the reaction proceeding, maybe it can help you.
Prantik, just now I saw your links just below the question. Note there are different reaction the azobis will be a radicalar initiator likewise a radicalar reation. The other link yes is about cycloaddtion.
Good luck