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

R
O
N
OX
SILYLATION OF NITRO COMPOUNDS AS A PROCESS 633
OSi
OMe
TfOSi (10%−20%)
CH2Cl2, −94 ° C
Si – Me2ButSi; X = Si: R = H (82%) * ; Me (86%); Et (87%); PhCH2 (89%);
MeO2C(CH2)2 (92%); NO2(CH2)3 (85%); Ph (89%);
4-MeOC6H4 (87%); SiO-N = CH(CH2)3 (58%) **
O
X = OEt: R = PhCH2 (61%); Et (57%).
*, the nitronate was prepared in situ
**, bis-C, C-coupling
Me
NuSi−
R
R′
NuSi−
Ph
O
+
N +
OSi
O
N +
OEt
Nu Si
TBSOTf −
Nu′−
Me
Nu′
R
N(OSi)2
OMe
(1)
Si – Me2Bu (2)
tSi TBS – SiMe2But OSi
OMe
Nu′–
Ph
O
NuSi−
OSi
O Nu′–
O
O
47% (1 equiv. TBSOTf,
dr > 10:1) 47% (0,2 equiv.
TBSOTf, dr = 1.2:1)
OSi
OMe
OSi
OMe
TfOSi (10%–20%)
O
SiO(XO)N
OMe
~100% (0.2 equiv. TBSOTf, dr = 1.2:1)
R′
SiO(EtO)N
R O
OMe
Si – Me2Bu t Si; R = R′ = Me (70%); instead R and R′ – (CH2)4– (63%); –(CH2)5– (71%)
R = Me, R′ = (CH2) 2CO 2Me (43%)
Scheme 3.208
The reaction is performed at −94 ◦ C in dichloromethane and, generally, in the
presence of catalytic amounts of silyl trißate. Although the reaction can be performed
with trimethylsilyl derivatives as well, it is advantageous to use hydrolytically
more stable SiMe2Bu t derivatives. The reaction of 1,4-dinitrobutane can
afford both mono- and bis-C,C-coupling products.
O
(3)