[kriggy]

I was doing wittig horner with o-nitro-benzaldehyde and cyanoethyl-phosphonic acid diethyl ester using EtOH:H₂O and 1eq of K₂CO₃ as a base and while the reaction should favor E-izomer i got 1:1 mixture of E/Z and some minor impurities. Is the reason for that bad ratio of e/z that I used K₂CO₃ instead of lithium based salt like LiOH?

I was also running nitro group reduction using SnCl2 in acetic acid:HCL mixture 10:1 and while doing workup - neutralizing with 30%KOH and then rising the pH to 14 followed by extraction to diethylether, it seems that my compound decomposed in such highly basic pH. Are there any way to get rid of the Sn⁴⁺ salts? Could be lower pH sufficient or is column my only option?

[TheUnassuming]

I don't think the counter ion has much of an effect on the E/Z ratio of WH.  More likely its due to the fact that your nitrile which provides the "bulk" to push the stereochemistry is gamma to the phosphonate as opposed to the traditional beta position of carbonyls ect.

Might be able to get away with a lower pH, but will probably have to go with a column (maybe more than one knowing Sn).  Fe/HCl reduction might be a viable alternative, and workup is traditionally much easier.

[kriggy]

hm I tried it with LiOH anyway so maybe it gets better. I can probably separate the isomers by crystalization but I would rather have higher % than 50..

Fortunately, there is like bilion methods to reduce nitro group Im thinking, when using SnCl2, how acidic pH is required for the reduction? I tried basic conditons that are used by our group on solid phase but not much succes there

[clarkstill]

I've never used any acid at all for SnCl2 reductions. You can just use it in refluxing ethyl acetate:

http://www.sciencedirect.com/science/article/pii/S0040403901800411

The tin residue is a b***h to get rid of though. My colleague just dilutes the workup to a ridiculous level; I normally add drops of NaHCO3 to the crude mixture in ethyl acetate - it causes the tin residue to crash out so you can decant the ethyl acetate away from the majority of it.

I also like the Zn powder/NH4Cl nitro reduction, e.g. here:

http://pubs.acs.org/doi/suppl/10.1021/ja808108q/suppl_file/ja808108q_si_001.pdf

- when it works it's super clean and done within about 5 mins.

[kriggy]

I tried that SnC₂ in ethanol. Didnt work for me I alredy was able to reduce the nitro group by Na₂S in EtOH but there is a problem with workup, but I guess I alredy figured it out