[mbckenny]

Hi,

I am trying to rearrange meso-hydrobenzoin ((1R,2S)-1,2-diphenylethane-1,2-diol ) to (1R,2R)-1,2-diphenylethane-1,2-diol (see pic for quick reference).

So basically just changing the chirality of one of the carbons, and keeping the other the same.

I've heard this can be done just with a strong base but I can't seem to find a paper on this anywhere - reaxys, WOS, google...

I've been looking at the Mitsunobu reaction, but I think that would spew out a mix of products as it would work on both alcohol groups?

Any ideas?

Thanks,

Mike

[sjb]

You can selectively e.g. tboc one of the hydroxyls using some desymmetrisation chemistry, such as (shameless plug) http://dx.doi.org/10.1021/jo0257041, then Mitsunobu on the free one, and hydrolyse / deboc, perhaps? Not sure how the project developed after I went, whether you'd be able to get clean enough 1R, 2R diol, but I think you can also buy it. Or epoxidise a stilbene of your choice, then ringopen the epoxide...?

[mbckenny]

Sweet, thanks that's a big help.

It's for a project and so I'm supposed to do it in this certain way, not allowed to use stilbene etc etc.

[Dan]

You can selectively e.g. tboc one of the hydroxyls using some desymmetrisation chemistry, such as (shameless plug) http://dx.doi.org/10.1021/jo0257041, then Mitsunobu on the free one, and hydrolyse / deboc, perhaps?

If I had a monoacylated diol, I would be worried about neighbouring group participation from the carbonyl in any attempt at displacement chemistry - and therefore expect retention of configuration.

If I was doing this I'd probably make a silyl ether (e.g. TBS), which should not participate in the displacement. Another option for the monoether is the benzhydryl ether, which can be introduced by treatment of a 1,2-diol with diphenyldiazomethane and cat. tin(II) halides (Example).

[sjb]

True, Dan, very good point. I seem to recall that some undergrad work was carried out using enantiomerically pure mandelic anhydride under these conditions and scrambling was not observed. That's not to say that Mitsunobu conditions would not also cause it too.