Chemistry Reference
In-Depth Information
Burgess reagent
O
O
_
S
+
_
CO
2
Me
+
Et
3
N
N
Et
3
NH + O
3
S-NH-CO
2
Me
+
H
_
O
O
+
R
a
N
R
R
H
H
N
H
1515
R
N
b
1513
NC
NC
O
88 %
1675
OTMS
61 %
1674
H
CN
NC
OAc
S
O
H
AcO
OAc
N
AcO
O
NC
H
H
CO
2
CHPh
2
72 %
1677
32 %
1678
82 %
1676
AcO
had been consumed (80 min). The resulting mixture was then cooled, diluted with
dichloromethane (20 mL), washed with water (2
20 mL), and dried (MgSO
4
).
Evaporation of the solvent in vacuo and dry flash chromatography of the residue
on silica gel 60, eluting with 5% dichloromethane in hexane, gave 3-isocyano-3,7-
dimethyl-octa-1,6-diene 1675 (0.14 g, 88%) as a clear oil, which darkened rapidly on
standing.
The Burgess reagent has been applied to the synthesis of isonitrile carborane
derivatives. This approach involved the dehydration of both boron- and carbon-
derived formamides. The products could be used as ligands for the synthesis of
transition metal based boron neutron capture therapy and synovectomy agents
(BNCS) and targeted radiopharmaceuticals. Isonitrile carborane 1680 has been
prepared in 51% yield by dehydration of the formamide 1679 with the Burgess
reagent under mild conditions (5 h reaction time at room temperature) [1244].
Typical procedure. 3-Isonitrile-1,2-dicarba-closo-dodecaborane 1680 [1244]:
The form-
amide 1679 (0.422 g, 2.25 mmol) was added to dry dichloromethane (30 mL)
with stirring. The Burgess reagent (1.07 g, 4.50 mmol) was added to the solution
as a solid under argon atmosphere. The homogeneous reaction mixture was
maintained at ambient temperature under dry nitrogen for 5 h, at which time TLC
indicated the complete consumption of the starting material. The solvent was
removed by rotary evaporation leaving a white solid, which was redissolved in
dichloromethane (25 mL) and extracted with distilled water (2
25 mL). The
aqueous layers were combined and further extracted with dichloromethane (25
mL) and diethyl ether (25 mL). All the organic phases were pooled, dried over
