Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

REACTIONS OF NITRILE OXIDES 81
Benzonitrile oxide reacts with nitrosobenzene to give α-nitrosonitrone
PhN(O) = CPhNO, which cyclizes to hydroxyphenylbenzimidazole oxide 380
and/or benzoxadiazine 381 (R = Ph). Similar reactions of PhNO with
p-MeC6H4CNO and EtO2CCNO give 381 (R = p-tolyl and CO2Et). Nitrosomesitylene
2,4,6-Me3C6H2NO reacts with PhCNO and p-MeC6H4CNO to give
α-nitrosonitrones 2,4,6-Me3C6H2N(O) = CRNO (R = Ph, p-tolyl), which do not
undergo cyclization reactions (429).
O
N
Ph
H
N R
N
OH O N
380 381
Arenecarbonitrile oxides react with alkyl (p-nitrophenyl)carbamates at the
nitro group, the nitrogen atom of the latter being the nucleophilic center. Tautomeric
N-hydroxybenzimidazole N-oxides 382 and 383 form as the Þnal products
(430).
RO2CNH RO2CNH
NO
N Ar
OH
382 383
NOH
N Ar
Benzo-as-triazine tri-N-oxides 384 (R = H, Me; R 1 = mesityl, 2,6-ClC6H3)
are formed from the reaction of nitrile oxides R 1 CNO with benzofuroxans 385.
The structure of 384 (R = Me, R 1 = mesityl) has been conÞrmed by X-ray crystal
structure analysis (431).
R
R
O
N
N
O
R
NO
1 O R
N
O
R
N
384 385
The efÞciency and limitations of 3-oxabicyclo[3.2.0]hept-6-ene-2,4-dione 386
(cyclobut-3-ene-1,2-dicarboxylic anhydride) as an acetylene equivalent in 1,3dipolar
cycloadditions has been reported. It reacted readily with a variety of
reagents, including nitrile oxides. In all cases, the sterically favored anti-isomers