42 Synthetic Routes to AliphaticC-Nitro
CCH 2 OAc
NO 2
Br
NO 2
CCH 2 OAc
O 2 N
KO 2 N
NO 2
NO 2
H
H
NO 2
NO 2
H
H H
2 SO 4
CCH 2 OAc
O 2 N
KO 2 N
CCH 2 C
NO 2
NO 2
CH 2 OAc
O 2 N
KO 2 N
HC
NO 2
CH 2 C
NO 2
NO 2
CH 2 OAc
NO 2
+ 2 KI + KBr + I 2
150
+ KOAc
154 155
65 % 68 %
155 156 157
Step 1
Step 2
Figure 1.71
iodide gave the potassium salt of 2,2,4,4-tetranitrobutyl acetate (156) in 65 % yield, which
on acidification with mineral acid, yielded 2,2,4,4-tetranitrobutyl acetate (157). Frankel^281
explained the unusual result by also postulating the formation of 1,1-dinitroethene, a highly
reactive intermediate capable of undergoing Michael type 1,4-addition with any unreacted
nitronate anion (155) present in solution. The generality of this reaction, known as ‘dini-
troethylation’, for the synthesis ofgem-dinitroaliphatic compounds is further illustrated by
the formation of the potassium salt of 1,1,3,3-tetranitrobutane when 2-bromo-2,2-dinitroethyl
acetate is treated with potassium iodide and the sodium salt of 1,1-dinitroethane.^281
NO 2
NO 2
H
H
H+
NO 2
NO 2
H
H
CCH 2 OH
KO 2 N
O 2 N
CCH 2 OH
KO 2 N
O 2 N
NO 2
C
NO 2
CH 2 OHH
CC
NO 2
NO 2
CH 2 OH
KO 2 N
O 2 N
20 150
+
158
- H 2 O
150
21
pH 4
70 %
20
Step 1
Step 2 CH 2
Figure 1.72
The formation of 1,1-dinitroethene (150) as an intermediate also accounts for the formation
of potassium 2,2,4,4-tetranitrobutanol (158) when a solution of potassium 2,2-dinitroethanol
(20) is partially acidified.^259 Klager and co-workers^259 postulated that 1,1-dinitroethene is
formed via elimination of water from 2,2-dinitroethanol and this rapidly undergoes Michael
1,4-addition with any potassium 2,2-dinitroethanol still present in the reaction mixture.
Demethylolation of (158) with potassium hydroxide yields the dipotassium salt of 1,1,3,3-
tetranitropropane.