Natural Science Forum / Chemistry / Organic Synthesis / October 2003

Hi, Witek!
pKa of indole is about 16.8 so u need a strong base (like Grignard
reagents) to deprotonate it (organic bases like amidines have pKaH about
12.6 and guanine 13 so they don't work).
I suggest u to use sodium metal to deprotonate the indole.
Regards,
Narcis

"Narcis Anghel" <nanghel@ch.tuiasi.ro> wrote in message news:<bn60hq$ftl@panther.Gsu.EDU>...

Hi, check out:
Organic Syntheses, Coll Vol. 6, p. 109

Direkt benzoylation at 3-position is difficult. You has to take a side
way to acieve the target.

3-Benzoylindole. A 100-ml., three-necked flask fitted with a magnetic
stirring bar, a condenser, and a pressure-equalizing dropping funnel
is charged with 0.48 g. (0.0060 mole) of copper(II) oxide, 1.61 g.
(0.0120 mole) of anhydrous copper(II) chloride (Note 8), and 40 ml. of
acetone. The resulting suspension is brought to reflux with vigorous
stirring, and a solution of 1.55 g. (0.00508 mole) of
3-(2-phenyl-1,3-dithian-2-yl)-1H-indole in 9 ml. of acetone and 1 ml.
of N,N-dimethylformamide is added over 5 minutes. Reflux temperatures
are maintained for 90 minutes, during which time the reaction mixture
gradually turns yellow, then the mixture is cooled and filtered. The
insoluble material is washed with three 20-ml. portions of hot 10%
ethanol in dichloromethane, and the combined organic solutions are
washed with 50 ml. of aqueous 2 N sodium carbonate (Note 9), dried
over sodium sulfate, and filtered. Concentration of the filtrate to a
small volume under reduced pressure gives a residue which gradually
deposits crystals. Filtration provides 0.94&#8211;0.97 g.
(85&#8211;88%) of pure 3-benzoylindole, m.p. 238&#8211;240°.

That is taken from the cited reference in Org. Synthesis.

Maybe you should check out also:

www.unb.br/iq/labpesq/qo/olv/olv/about.htm