Chemistry Reference
In-Depth Information
18 h. The solvent was then removed in vacuo and the residue was taken up in Et
2
O
(50 mL). The remaining precipitate was removed by filtration and the filtrate
was concentrated to dryness in vacuo. Flash chromatography, eluting with 30%
Et
2
Oinn-hexane yielded 4-bromo-3-[2-isocyano-2-(methoxycarbonyl)ethyl]indole-1-
carboxylic acid tert-butyl ester 1559 as a white gum (0.05 g, 75%).
CO
2
Me
CO
2
Me
CO
2
Me
Br
Br
Br
NC
NC
NHCHO
(Cl
3
CO)
2
CO
LDA
allyl-
bromide
45 %
1560
Et
3
N
CH
2
Cl
2
N
N
N
75 %
1559
Boc
1558
Boc
Boc
rt, 18 h
HCl
CO
2
Me
CO
2
Me
CO
2
Me
CO
2
Me
NH-Z
NH-Z
Br
Br
NH
2
+
NH-Z
Z-Cl
N
N
95 %
1561
Pd(OAc)
2
Tol
3
P
N
N
H
H
H
H
70 %
1562
1564
88 %
1563
A further valuable tool in organic chemistry is facilitated by isocyanides: the de-
amination reaction. When the standard deamination reaction via a diazonium salt
is undesirable (due to a need to avoid acidic conditions), primary amines can be
converted by well-known methods into isocyanides, which are reduced using tri-
butyltin hydride under Barton's conditions (heating for 5 h at 80
C in toluene). This
reaction sequence has been applied as a new route to 1,3-polyols using azetidinone
frameworks 1565 as chiral templates [1188]. Dehydration of the formamide 1567
was accomplished with triphosgene to afford the isocyanide 1568, which was
reduced e
ciently with tris(trimethylsilyl)silane to afford the desired a,g-dialkoxy
ester 1569 in 80% yield [1188].
OBn
OBn
OBn
OBn
OBn
HCO
2
H
Ac
2
O
H
H
BnO
MeO
2
C
MeO
2
C
NH
1566
NH
2
1567
NHCHO
MeOH
O
CH
2
Cl
2
, Et
3
N
0°C, 15 h
1565
(Cl
3
CO)
2
CO
TMS
3
SiH
AIBN
OBn
OBn
OBn
OBn
MeO
2
C
MeO
2
C
toluene
80°C
30 min
80 %
1569
1568
NC
