[Babcock_Hall]

We have used Masamune-Roush conditions in Horner Wadsworth Emmons reactions with good results on a number of occasions.  Last week we had a rare failure using 5-nitrofuraldehyde and diethyl methylsulfonylmethylphosphonate, with DBU as the base.  So far the only product that I have identified by NMR is the phosphonate starting material.  There may be some aldehyde remaining.  TLC with UV detection showed many spots, some of which faded with time.

Does this furan have a propensity to react in other ways?  I am told it may do single electron chemistry, but I don't have a reference for this.  If we substituted the corresponding thiophene for this furan, are we likely to do any better?  Thanks for any ideas.

[Babcock_Hall]

One more modest point of interest.  The darkness of the color waxed and waned over the fractions.  Yet, the first two pools that we analyzed by H-1 NMR were nearly pure diethyl methylsulfonylmethylphosphonate, the colorless starting material.

[Babcock_Hall]

Furan is weakly aromatic, and thiophene is strongly aromatic.  That may tip the balance in favor of a Horner reaction with respect to thiophene.

[Babcock_Hall]

The corresponding thiophene-based aldehyde gave a more typical reaction and was purified with little difficulty.  Although there was at least one other product, it moved much more slowly through the silica column, and we have not attempted to isolate it.

[Babcock_Hall]

Would the corresponding reaction with formylnitropyrrole behave more like the furan (which failed) or the thiophene (which succeeded), or do we just have to try it and see?  The pyrrole is intermediate in aromaticity between the furan and the thiophene, so I don't know.

Would replacing the nitro group with a carboxylate ester change the reaction for either a furan or a pyrrole.  My sense is that the carboxylate group is less electron-withdrawing, but I don't have a feel for how much. 

[rolnor]

I think pyroll is much more aromatic in character than furan, so yes, I think it will be similar to thiophene. Yes, carboxylate is less EW than nitro, hard to say how much. As you suggest, just try, there is good hope.