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

SYNTHESIS OF NITRONES 159
In a similar procedure, through diisobutylaluminium hydride (DIBALH)reduction
of nitrile into imine and condensation with N-benzylhydroxylamine,
C -(1-ßuorovinyl) nitrones were synthesized (Scheme 2.30, Table 2.4) (228).
To obtain materials with increased contrast range at light exposure with wavelength
300 to 450 nm, nitrones soluble in alkali have been prepared (229).
A number of α-aryl-N -alkyl nitrones and α,N -dialkyl nitrones were synthesized
for studying contrast enhancement compositions, which can be used to make
contrast enhancement layer photoresist composites (230, 231), and inhibitors of
free radical polymerization of monomers in nonexposed regions of the photoresist
layer at selective actinic radiation (232). Histidine was used as a catalyst in the
synthesis of α,N -diaryl nitrones in situ (233). To study diphenylborate chelates
with mono- and bidentate ligands, a series of hydroxyl-containing nitrones have
been synthesized (Fig. 2.7) (234–237).
R 1
R 2 F
CN
1. DIBALH
2. MeOH
3. BnNHOH
Scheme 2.30
Table 2.4 Synthesis of C-(1-ßuorovinyl)nitrones
R1 N
O− +
R2 F
83a–f
Substrate(R 1 R 2 C=0) Yield(%) (E)/(Z)(C=N)
a 3-Phenylpropanl 79 < 2:98
b Benzyloxyacetaldehyde 18 < 2:98
c tert-Butylcyclohexanone 81 10:90
d 1,4-Dioxaspiro[4,5]cyclodecan-8-one 93 10:90
e Cyclododecanone 98 < 5:95 (20:80)
f Adamantanone 67 2:98 (4:96)
+
OH O−
Ref. 234
H
N Ar
H
+
Ref. 235
Ar
O
OH
−
N
R 2
Fig. 2.7
R 1
OH
O N
−
HO
Ref. 236
+
Bn
R2
R 1
N R +
OH O −
Ref. 237