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

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PRINCIPAL PHYSICOCHEMICAL DATA AND CHARACTERISTICS 499<br />

Table 3.9 Characteristic UV <strong>and</strong> IR absorbance for various nitronates. a<br />

Entry Nitronate λmax nm (ɛ) IRC=N cm −1 Ref.<br />

1 MeCH=N(O)OSiMe3 240 (5.1·103 2 Me2C=N(O)OSiMe3<br />

)<br />

240 (7.0·10<br />

1622 205<br />

3 3 PhCH=N(O)OSiMe3<br />

)<br />

280 (7.0·10<br />

1626 205<br />

3 4<br />

p-Br-C6H O<br />

4<br />

N<br />

)<br />

288 (32.7·10<br />

1590 205<br />

H OMe<br />

3 ) 1610–1620 237<br />

5<br />

6<br />

CF3CH=N(O)OSiMe3<br />

MeO2CCH=N(O)OSiMe3<br />

—<br />

265 (10.0·10<br />

1610 132<br />

3 ) 1590 1739<br />

(C=O)<br />

203<br />

7 (MeO2C)2C=N(O)OSiMe3 271<br />

(∼5.0·103 ) b , c<br />

1580 1750<br />

(C=O)<br />

268<br />

8 R OBEt2O<br />

N N<br />

R′ OBEt2O<br />

R′<br />

R<br />

R = H or alkyl<br />

R′ = alkyl<br />

228–235<br />

((10.2–10.7)·103 9<br />

AcO<br />

O<br />

)<br />

272 (26<br />

1615–1650 229<br />

N CH CH CH CH N<br />

O<br />

OAc<br />

. 103 ) 1585 224<br />

10<br />

NO2<br />

320 (8.3·103 ) 1620 259<br />

11<br />

12<br />

13<br />

14<br />

15<br />

G*O<br />

O N<br />

O<br />

Ph<br />

O N<br />

Ph<br />

O N<br />

O<br />

G*–axilary<br />

— 1620 57<br />

— 1626 140<br />

O<br />

Ph 288 (11.6·103 ) 1590 92<br />

O N O<br />

Me 234 (5.0 . 103 ) — 92<br />

O N O<br />

CO2Me — 1570 92<br />

O N O<br />

a For nitroalkanes: λmax = 210 nm (ɛ∼1 . 10 4 )<strong>and</strong>λmax 270–280 nm (ɛ∼20); vas∼1550–1560 cm −1 266.<br />

b For nitronate 73a λmax = 265 nm (ɛ = 11.0 . 10 3 ) 235<br />

c In KR-spectra νC=N= 1590 cm −1 (ρ = 0.44) 203

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