Hi, I am trying to make an amide from 4-bromo thiazole 2-carboxylic acid and 2-amino pyridine using HBTU, TEA, DMF. At first trial, I preactivated the acid with 1.2 eq of HBTU, 4 eq of TEA but after 3 hours I couldn't detect the intermediate or the consumption of my acid. At the second trial, I used 1 eq of HBTU, 1 eq of HOBt, 4eq of TEA and reduced the time to 30 mins, but the same situation happened. In both case, amine addition after preactivation made no change. I wonder what wrong did I make and how can I improve this coupling procedure?