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

R 2
R 1
Cl
Ph O
·
Cl
Ph N
OR
Ph N
SYNTHESIS OF NITRONES 163
CH2Ph
NH
i ii iii
Ph
(i) tBuONH2 HCl, NaOAc, MeOH, 20°C
(ii) PhCH2NH2, DMF, 20°C
(iii) BH3 · THF, 0 - 20°C; then 6M HCl
(iv) conc. H2SO4, MeOH; then HCl (g), Et2O (v) HC(OEt) 3, PhMe, 60°C
O + MeN
89
OSiMe 3
OSiMe3
50°C
PhH
Scheme 2.33
Me3SiO N
1 2 R RC
N
N
OSiMe 3
OR
CH2Ph
v
Ph N
Ph N
iv
CH2Ph
NH
O
OH
88 87
Me
a: R = Bu t
b: R = CH 2Ph
c: R = H
R 2
CH2Ph
NH
OR
a: R = Bu t
b: R = CH 2Ph
O
N
R1 + + Me3SiOSiMe3 Me
R 1 = Ph, p(Me 2N)C 6H 4, p −(O 2N)C 6H 4, 2 −furyl, −(CH 2) 3 CH=CH 2, Pr i , Bu t , or Me
R 2 = H or Me
R 1 + R 2 = −(CH 2) 3 −
Scheme 2.34
a series of 1,3-diphenyl-3-hydroxyimino-N -(1’-methylidene)-1-propylamine N -
oxides (92) (Scheme 2.35) (259).
Nitrones resulting from the condensation of aldehydes and ketones with N -
monosubstituted hydroxylamines were used in a four component Ugi reaction in
a one-pot synthesis of α-acyloxyamino-amides (260).
The synthesis of optically active nitrones (95) was carried out by an aldol
reaction of aldehydes (93), catalyzed by L- proline, with carbonyl activated compounds
(94) and by an in situ reaction with N -alkylhydroxylamines (Scheme
2.36, Table 2.5) (261).
90
−