[pianoteam]

Hi everyone,

This is my first time posting here and I wanted to kindly ask for some advice on getting an oxidation reaction to work. The substrate is very simple (5-hexen-1-ol) but it has plagued me with countless difficulties. I am trying to synthesize an aldehyde from this alcohol and have tried using PCC, the Swern oxidation and DMP. This substrate has been used with all these reagents successfully in the literature although I am having a hard time pinpoint my problem. The Swern oxidation seems to give me either the thioacetal side product or carboxylic acid and I am not interested in pursuing this further because of the difficulty in set-up and bad smell. PCC and DMP I got to work before with dilute conditions (0.1 M) but with low yield (<25 %) although I could not purify the crude product as it seemed to degrade/autoxidize in a day or two (even under vacuum or N2) so I plan to use the crude product in my following reaction. I have decided to stick with DMP just because with PCC it is challenging to remove all of the chromium salts. Unfortunately with DMP I am still seeing the carboxylic acid as the major product (lately less than 10 % yield) and am quite perplexed as I use anhydrous DCM as well as an oven dried flask/stir bar and perform the reaction under an inert nitrogen atmosphere. Also the DMP was purchased about a month ago and I am the only one using it. The conditions I use are 1.2 eq DMP and 1 eq alocohol (0.1 M solution in DCM). Does anyone know where I could be going wrong with this? It is very frustrating as this should be a simple reaction to carry out yet it is giving me a very difficult time. My supervisor suggested converting this substrate to the methyl ester and using DIBAL to generate the aldehyde - would this be a better route despite having more steps?

[Borek]

Please don't cross post.

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