42 Synthetic Routes to AliphaticC-Nitro
CCH 2 OAcNO 2
BrNO 2CCH 2 OAc
O 2 NKO 2 NNO 2NO 2HHNO 2NO 2HH H
2 SO 4
CCH 2 OAc
O 2 NKO 2 N
CCH 2 CNO 2NO 2CH 2 OAc
O 2 NKO 2 N
HCNO 2CH 2 CNO 2NO 2CH 2 OAcNO 2+ 2 KI + KBr + I 2150+ KOAc154 15565 % 68 %155 156 157Step 1Step 2Figure 1.71iodide 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 2NO 2HHH+NO 2NO 2HHCCH 2 OHKO 2 NO 2 NCCH 2 OHKO 2 NO 2 NNO 2C
NO 2CH 2 OHHCCNO 2NO 2CH 2 OHKO 2 NO 2 N20 150+158- H 2 O
15021pH 4
70 %20Step 1Step 2 CH 2Figure 1.72The 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.