[Limpet Chicken]

Hey guys.

I have been looking at indane, for organic reactions, and wish to regioselectively formylate, what I can't work out however, is how to insure the reaction takes place at the 5 position, would simple reflux with 80% formic acid work, maybe even 40% strength, or are more advanced means neccessary?

Thanks all.

[Mitch]

where is the 5 position?

[Limpet Chicken]

I cannot actually find any reference to the structure at all, and it brings up a total of two somewhat irrelevant results on google   (searching under 5-formylindane)

[Mitch]

here is a pic of indane. I'm familiar with it from research, but I'm too lazy to go look-up where the 5 position is.

[Limpet Chicken]

I just realised something, I didn't mean to type indane at all, I was looking for 5-formyl indENE, I was just thinking of indane at the time I typed, I meant indene lol

[movies]

I would suspect that standard aryl formylation reactions would give the 5-formyl product since an alkyl group is a somewhat stronger electron donating group than an olefin.  You're bound to get a bad mixture however.

Some standard formylation reactions, some better (easier) than others.  I wouldn't recommend any of them, really:

Gatterman (Zn(CN)₂ + HCl)
Gattermann-Koch (aromatic + CO + HCl + AlCl₃ + Cu₂Cl₂)
Vilsmeier-Haack (DMF + POCl₃)

Selective functionalization of the aromatic ring in indenes, indanes, and indoles are a very common and very difficult problem in synthesis.

[movies]

By the way, the numbering is analogous to that of indole.  C1 is the aliphatic carbon of the cyclopentane ring, then count around the exterior carbons starting with the 5 membered ring, skipping the bridghead carbons, they are last.

Check out the IUPAC web site for more on numbering fused ring systems:

http://www.chem.qmul.ac.uk/iupac/fusedring/