acylbenzotriazoles 6.1a-g in the presence of TiC14. Similarly, reactions of N-
methylindole (6.11) gave the corresponding acylated N-methylindoles 6.12a-g in
27-92% yields (Table 6-3). Novel 3-acylated indoles were characterized by their 1H and
13C NMR spectra and elemental analysis. The complications observed earlier in the
acylation of unsubstituted indole, such as simultaneous formation of 1-acylated and/or
1,3-diacylated products were absent. [70Indoles] [72CHC116] Our method also removes
the possibility of decomposition or self-polymerization of indole commonly observed due
to the release of HCl when acyl chlorides are employed. [01OL1005]
0
TiCI4
S + RCOBt 2\
N CH2C12 N
X 6.1a-g 250C,2h X
6.9: X=H 6.10: X=H
6.11: X= Me 6.12: X= Me
Scheme 6-3. 3-Acylation of indole (6.9) and 1-methylindole (6.11) using N-
Acylbenzotriazoles 6.1a-g.
Table 6-3. Preparation of 3-acylated indole (6.9) and 1-methylindole (6.11).
Reactants R Product Previous work
(Yield %)a
6.9+6.1a 4-CH3C6H4 6.10a (88) [65CA10415b]b
6.9+6.1b 4-NO2C6H4 6.10b (66) [01CPB799]C
6.9+6.1c 4-Et2NC6H4 6.10c (43) --
6.9+6.1d 2-furyl 6.10d (64) [00OL1485]d
6.9+6.1e 2-pyridyl 6.10e (73) [77JOC1213]e
6.9+6.1f 2-indolyl 6.10f (86) [02CA336939f
6.9+6.1g 2-pyrrolyl 6.10g (15) --
6.11+6.1a 4-CH3C6H4 6.12a (92) [97H347]g
6.11+6.1b 4-NO2C6H4 6.12b (74)
6.11+6.1c 4-Et2NC6H4 6.12c (79)
6.11+6.1d 2-furyl 6.12d (90)
6.11+6.1e 2-pyridyl 6.12e (70)
6.11+6.1f 2-indolyl 6.12f (27)
6.11+6.1g 2-pyrrolyl 6.12g (48) --