▁an ▁intr am ole cular ▁ 5 - ex o - dig ▁cycl ization . ▁This ▁cycl ization ▁forms ▁a ▁ 5 - im ino - 2 - th ione ▁th ia z olid ine ▁comp ound ▁that ▁under go es ▁a ▁t aut omer ization ▁when ▁a ▁base , ▁such ▁as ▁water , ▁abstract s ▁the ▁hyd rog ens ▁at ▁positions ▁ 3 ▁and ▁ 4 . ▁The ▁electrons ▁from ▁the ▁carbon - h ydro gen ▁s igma ▁bond ▁are ▁pushed ▁back ▁into ▁the ▁th ia z ole ▁ring , ▁forming ▁two ▁new ▁double ▁b onds ▁with ▁the ▁adjacent ▁carbon ▁atoms , ▁and ▁catal yz ing ▁the ▁formation ▁of ▁two ▁new ▁nit ro gen - h ydro gen , ▁and ▁sul fur - h ydro gen ▁s igma ▁b onds . ▁This ▁t aut omer ization ▁occurs ▁because ▁it ▁is ▁therm od ynam ically ▁fav ou rable , ▁yield ing ▁the ▁a rom atic ▁final ▁product : ▁ 5 - amin oth ia z ole . ▁ ▁App lications ▁ ▁F ew ▁instances ▁of ▁applications ▁of ▁the ▁Cook – He il br on ▁th ia z ole ▁synth esis ▁are ▁found ▁in ▁literature . ▁In ▁recent ▁years , ▁modifications ▁of ▁the ▁H ant z sch ▁th ia z ole ▁synth esis ▁are ▁the ▁most ▁common , ▁partly ▁because ▁of ▁its ▁ease ▁in ▁introdu cing ▁R - ▁group ▁divers ity . ▁ ▁However , ▁in ▁ 2 0 0 8 ▁Scott ▁et ▁al . ▁employed ▁a ▁Cook - He il br on ▁synth