[Woodwardt84]

Hi Guys

Im trying to repeat this "easy" reaction with no success after several tries. Any one that ma have any idea why?

[S-(S,S)- and R-(R,R)]-5,6,7,12,13,14-Hexahydro-6,13- methanocycloocta[1,2-b:5,6-b′]diindoles 4. To a stirred and heated mixture of phenylhydrazine (0.12 g, 1.1 mmol) in an ethanol-water mixture (5 mL, 90%) acidified with 0.1 mL of hydrochloric acid was added (-)-(1R,5R)-dione 1 (0.084 g, 0.55 mmol, [R]20D ) -149°) or the corresponding (+)-(1S,5S)-dione 1. The reaction mixture was refluxed for 20 min, cooled, and left to crystallize. The crystals were filtered and washed with water and ethanol. Recrystallization from acetone gave diin- dole 4 (0.13 g, 65% yield)

[Arctic-Nation]

When you say that the reaction fails, how does it fail? Recovery of starting products, complicated mixture of compounds, formation of black tar? Only if you know what the problem is, you can find a solution to it.

If you just recover your starting products, increase the reaction time. Twenty minutes at reflux seems awfully short for a classical Fischer indole synthesis. I'm also not really a fan of heating minute quantities of HCl to the boiling point, and using a different acid catalyst (sulfuric acid, pTSA) might work.

If you get black tar, try adding less acid.

[orgopete]

I haven't done any Fisher indole syntheses, so this is just an opinion. I would expect that a reaction should take place. I think the cyclization is going to be the problem. It isn't a Bredt's rule violation, but it should be strained, so the reaction should be retarded.

Let us digress a moment, "easy"? I am unfamiliar with the product being attempted. Is this a literature product and that is the procedure or is that a literature procedure for another Fisher indole synthesis?