2-Bromo-2-formyl-pent-3-endioic anhydride OR 4-Bromo-4-formyl-pent-2-endioic anhydride ?

@Wolgwang 4-Bromo-4-formyl-pent-2-endioic anhydride

Thanks

@YashAgrawal I'm guessing its a typo and it should be a benzene ring..

@YashAgrawal firstly, such a question will always have many many products in reality, so you really have to try out a few things and see which option matches.

One possibility is that the H+ converted the OH to OH2+ and it leaves, forming a carbocation which has two resonance structs

This carbocation will likely attack the other alkene (on the left) to form a ring and a new carbocation.

@AshishAhuja will it be a major product amongst the rest? because before attacking alkenes, acid-base reaction will take place first with alcohol?

give me a second I'm just uploading my mechanism for the product formation...

(there are obviously many more possibilities, but I've shown the two most likely you get for each resonance structure)

@hansika yes, I feel that an electrophilic attack on an alkene has to be slower than simply attacking the alcohol to form a carbocation, because of two reasons:

(1) as you said, acid-base is faster, and an alkene is not extremely electron rich (2) in this case, by dehydrating the alcohol to get a carbocation we get a resonance stabilised carbocation while attacking either of the alkenes first gives us a much more unstable carbocation; so attacking the alcohol first makes much more sense to me (lower activation energy to first TS)

cool..thank you!

does anyone have pdf of clayden?

bit.ly/3142oLk

@YusufHasan thank you so much!