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Topic: HBTU coupling preactivation  (Read 1454 times)

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Offline vu_nam

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HBTU coupling preactivation
« on: April 03, 2014, 12:03:10 AM »
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?

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