CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

14. 1n C 6 H 5 CO C 6 H 5 2n 8 77
15. 1o C 6 H 5 CH=CH Ph 2o 8 81
16. 1p Cyclohexanone 2p 7 78
17. 1q 2-Methylcyclohexanone 2q 7 77
a The reactions were carried out at 2 mmol scale using 50 mol% In. The yields refer to
those of isolated pure products.
However, formation of III followed an absolutely novel mechanism. Initially,
reaction between [bmim][Br] and Ga produced a Ga-N-heterocyclic carbene complex
[NHC-GaBr(OH) 2 ] (IIIa) that required presence of O 2 . Evidently, the initially formed
charge transfer-
H H
Br
H
N N
3 C C 4 H 9
H
[BMIM][Br]
H
H
N δ
1 / 4 O 2
H
N
3 C C 4 H 9 Br
H
N N
3 C C 4 H 9
+ GaBr
H
Ga +δ H
1 / 4 O 2
H
H
H H
H 3 C
N N
C 4 H 9
H
H
C 4 H 9
N OH
Ga Br
N OH
Br
O
R 1 R 2
GaBr
H 2 O
R 1
R 2
OH
+ 1 / 2 H 2 O
IIIa
III
2
Scheme 3
like transient Ga-[bmim][Br] transferred electron to O 2 to form O -. 2 , which got stabilized
by the C-8 acidic proton of the imidazole moiety. Subsequent decomposition of the
intermediate generated the NHC diradical, which on reaction with Ga furnished IIIa. The
species was fully characterized by spectral (IR, NMR, MS) data, as well as
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