Chemistry Reference
In-Depth Information
Aromatic compounds are formylated using triphosgene/DMF [1300], phosphorus
oxychloride/DMF,oroxalyl chloride/DMF [1301].
N,N-Dimethylaniline 1771 was treated with Vilsmeier complex 1770 (prepared
by reaction of DMF with triphosgene below 20
C for 10-30 min) in DMF at 90-
95
C for 2 h to give p-Me
2
NC
6
H
4
CHO 1772 in 82% yield [1300].
An e
cient synthesis of 2,4-dihydroxybenzaldehyde 1775 from resorcinol 1773
by a Vilsmeier-Haack reaction using either phosphorus oxychloride/DMF or oxalyl
chloride/DMF, working below room temperature in acetonitrile, has been reported
[1301].
Cl
CHO
1. DMF
Cl
N
+
90-95 °C, 2 h
N
N
1770
2. H
2
O
82 %
1772
OH
1771
(CCl
3
O)
2
CO
+ DMF
H
2
O, 50°C
N
(COCl)
2
/DMF
MeCN
Cl
OH
H
HO
66-70 %
overall yield
OH
1774a
O
HO
OH
HO
1775
O
1773
POCl
3
/DMF
MeCN
N
H
2
O, 50°C
70-75 %
overall yield
Cl
P
O
HO
Cl
1774b
A triphosgene-based procedure for the convenient preparation of large quantities
of the strong, non-nucleophilic base 2-tert-butyl-1,1,3,3-tetramethylguanidine 1779
has been described [1302].
2-tert-Butyl-1,1,3,3-tetramethylguanidine 1779 provides an inexpensive alterna-
tive to the amidine bases, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (DBU), which suffer from being easily alkylated. Addi-
tionally, the hazards of using phosgene in the previous preparations [1303-1307]
are reduced by employing triphosgene.
COCl
Cl
O
O
(CCl
3
O)
2
CO
Me
NN
Me
Me
Me
NN
Me
Me
Cl
Me
Me
Cl
N
N
- CO
2
Toluene, 0°C
Me
1778
Me
Me
Me
1776
1777
t-BuNH
2
- 2 HCl
t-Bu
N
Me
NN
Me
Me
Me
1779
