eth ox y - 2 - ben zy l th ia z ole ▁by ▁react ing ▁d ith i oph eny lac etic ▁acid ▁with ▁am ino ac eton it rile ▁and ▁eth yl ▁am in ocy ano ac et ate , ▁respectively . ▁Sub sequ ent ▁experiments ▁by ▁Cook ▁and ▁Heil br on , ▁detailed ▁in ▁their ▁series ▁of ▁publications ▁titled ▁“ St ud ies ▁in ▁the ▁Az ole ▁Series ” ▁describe ▁early ▁attempts ▁to ▁expand ▁the ▁scope ▁of ▁ 5 - amin oth ia z ole ▁synth esis , ▁as ▁well ▁as ▁employ ▁ 5 - amin oth ia z oles ▁in ▁the ▁formation ▁of ▁pur ines ▁and ▁py rid ines . ▁ ▁Mechan ism ▁▁ ▁In ▁the ▁first ▁step ▁of ▁the ▁reaction ▁mechanism ▁for ▁the ▁synth esis ▁of ▁a ▁ 5 - amin oth ia z ole ▁from ▁an ▁ ▁α - amin on it rile ▁and ▁carbon ▁dis ul ph ide , ▁a ▁l one ▁pair ▁on ▁the ▁nit ro gen ▁of ▁the ▁α - amin on it rile ▁performs ▁a ▁nucle oph il ic ▁attack ▁on ▁the ▁slightly ▁electro pos itive ▁carbon ▁of ▁car b ond is ulf ide . ▁This ▁addition ▁reaction ▁push es ▁electrons ▁from ▁the ▁carbon - s ulf ur ▁double ▁bond ▁onto ▁one ▁of ▁the ▁sul fur ▁atoms . ▁Act ing ▁as ▁a ▁Lewis ▁Base , ▁the ▁sul fur ▁atom ▁don ates ▁its ▁electrons ▁to ▁the ▁carbon ▁atom ▁of ▁the ▁nit rile , ▁forming ▁a ▁sul fur - car bon ▁s igma ▁bond ▁in