Hello,
I am having trouble derivatizing two secondary alcohols with MTPA-Cl under widely used experimental conditions. I have tried using just pyridine and pyridine+DMAP as catalysts but that does not seem to work. Both reactions were in pyridine. The reactions were run for ~24 hours and in an anhydrous environment.
Does anyone have any suggestions for a stronger catalyst or set of reaction conditions to improve derivatization of secondary alcohols with R/S-MTPA-Cl?
Thanks,
Peter
Sullivan
You are using the right standard procedures for this reaction ! You may have bulky groups in your sec. alcohols preventing this reaction to take place. ! You should run the reaction under N2 atmosphere
--- (R)-or (S)-MTPA chloride (79.2 mmol, 15 mL) was added to a solution of pyridine (13 mL) and a secondary alcohol (95 mmol) in dry CH2Cl2 (1 mL) under nitrogen atmosphere and stirred for 1–2 days. The solvent was evaporated and the residue was purified by PLC (hexane/AcOEt = 6:1) to give amethoxy-a-(trifluoromethyl)-phenylacetic acid ester of a secondary alcohol.
--- Takahashi, Tamiko et al Journal of Fluorine Chemistry, 127(6), 760-768; 2006
I did a short survey for you (enclosed)
Good luck
Try to perform the reaction using ultrasonic bath instead of heating ( reflux) , to reduce the time and increase the yield. Ultrasound technique is an excellent source of energy.
https://dash.harvard.edu/bitstream/handle/1/11030585/Brown_gsas.harvard_0084L_11009.pdf?sequence=3
Thanks for your responses! It is possible that a phenyl group is getting in the way of derivatizing one of the alcohols. But the other alcohol does not have any bulky group around it.
I have been running the rxn in a nitrogen atmosphere FYI.
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