Hey Guys,
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Disclaimer: Not to waste your time reading this: if you have never worked with IBX or benzylic oxidations, I get very specific. -
So my situation is that I want to use IBX to oxidize a Benzylic CH2 Group to a ketone. This method is reported by K. C. Nicolaou (Am. Chem. Soc., 2002, 124, 2245-2258, https://www.organic-chemistry.org/abstracts/literature/039.shtm). However, when I tried to use this reaction on my "target molecule" nothing happened (checked with LCMS). Therefore, I tried to reproduce the exact reaction from the paper: using toluene as substrate with dry DMSO as solvent and 3 eq. of IBX at 80 °C. After 3 h, I didn't observe any formation of the product, benzaldehyde, at all (HPLC), thought toluene was present.
Regarding the IBX I'm using: I synthesized it myself (according to the procedure referred to in the paper) but I also tried the commercial one (50% H2O) in the beginning. Neither worked. Upon addition of my IBX, I get a clear solution after 10 min in DMSO, in DMSO:PhF 1:2 some IBX remains undissolved. I also tried over night reaction in DMSO and a second wash/dry purification for the IBX. (Though NMR data of IBX did not even show any impurity prior to this) . I employed an alcohol Oxidation as test reaction for the reactivity of my IBX: I selected Benzylalchol, which is reportedly oxidized by IBX within 15 min to Benzaldehyde (DMSO on air at r.t.). It worked. Confirmed by HPLC, consumption of starting material and smell ;).
So my IBX seems active but unable to perform a Benzylic CH2 Oxidation neither to my "target compound" nor toluene, the latter was reported to be oxidized by IBX in the paper.
I don't want to claim the paper "lies" but I am unable to reproduce the result. Especially regarding that Nicolaou is a renowned chemist. Does anyone ever have experienced something like this with organic chemistry reactions aswell?
Maybe one of you has experience with the reaction figures what's wrong. Maybe I am missing something or there is a trick to it? I would really like to get it to work. At least on toluene. If it does not work my target molecule - fine. But I can't get over the fact, that I can't reproduce the result from the paper. Hard to sleep at night
