[Doc Oc]

Anyone ever done a Luche reduction with a substrate that isn't soluble in methanol?  I've tried various conditions (THF/MeOH, MeCN/MeOH, THF/MeOH/H₂O, etc) and none seem to work.  I used sodium triacetoxyborohydride in THF and got a tiny bit of product after an hour, but stirring longer than that led to disappearance of it.

I can't resort to stronger hydride sources because there are esters I need to preserve.

[Babcock_Hall]

I don't have any personal experience, but I found what looked like an interesting reference:
 This method improves the standard Luche reduction by replacing expensive lanthanide salts with inexpensive, readily available calcium salts. (Green Chem. 2012, 14, 2129–2132; José C. Barros)
http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_ARTICLEMAIN&node_id=840&content_id=CNBP_030604&use_sec=true&sec_url_var=region1&__uuid=c66eed0f-c08b-45dd-b3f8-0c0321c0484a

[Dan]

none seem to work.

In the sense of no conversion or in the sense of side reactions?

I have never done a Luche, but I've done sodium borohydride reductions on substrate insoluble in MeOH and found MeOH/t-BuOH and MeOH/DCM mixtures worked fine. Not sure that helps you but I thought I'd mention it anyway.

[Doc Oc]

Thanks for the reference Babcock_Hall, I'm definitely gonna give that paper a look.

Dan, there's little to no conversion, even after 24 h of stirring.  Luche reductions (at least the ones I've done) are usually done in 30-60 min.  I haven't tried DCM or t-BuOH yet, I'll give it a shot.  These binary solvent combos are easy to try, so I don't mind.

[Dan]

Maybe the low conversion is due to the hydride source rather than the solvent. You could also try NaBH₄ at low temp. You should get chemoselectivity over the esters - have you tried it already?.

[Doc Oc]

I did try straight NaBH₄ in methanol, but I didn't cool the reaction.  Maybe I'll give that a shot.