I tried to cyclise this (E)-2,3-di(thiophen-2-yl)acrylic acid to form cyclic ketone through Friedel Crafts reaction. The condition was forming the acid chloride using oxalyl chloride in anhydrous DCM with a few drop DMF as catalyst at 0 degree C until RT. Then, I tried to cyclise with AlCl3 in anhydrous DCM at 0 degree C until RT. However, it did not seem to work. Some modifications of the reaction condition has been made, but they did not work as well. I still do not find any reason why it did not work. However, do you have any suggestion?
Sir if you provide the name of product or the step at which reaction is not feasible, it will be easier to answer.
In first step, you can use SOCl2 or PCl5 for the substitution of OH group with Cl in the presence of DCM or Chloroform as solvent.
Also May be the end product is 4 membered cyclic structure which has high angle strain and unstable.
I agree with Navjot Sethi recommendations.
Also try carrying out the reactions at 25 oC (RT) rather than 0degree C
How much AlCl3 did you use? The resulting ketone forms a complex with AlCl3 but so does thiophen also. Article ISSN 1984-6428 ONLINE A Theoretical investigation of furan-A...
Jukka Salminen I used 1.0 eq to the starting material. That might be something that I have never thought of before because I don't think complex formation can possibly occur. As I read two of the references I used, they was successful in doing the ring closing.
Babajide Alo Sure, I have also carrying the reaction at RT as well.
Navjot Singh Sethi But it is only OH group was replaced by Cl and the Cl left as a result, my guess, the acylium ion would attack 3 position on thiophene forming 5 membered ring with ketone instead of 4 ring.
Thiophene is not stable with electrophilic substitution at position 3, May be that reason the reaction is not being completed or the yield will be lower
I agree wit Dr.hNavjot Singh Sethi, based on the resonating structures of the thiohene, that confirm the high electron density of 2 and 5 positions than the susceptible cyclization 3 and 4 positions.So, i suggest to either to activate this thiohene ring or increase the equivalence of the anhydrous AlCl3 and be sure it is very anhydrous reagent.
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