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

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R<br />

R<br />

495<br />

NO2<br />

493<br />

N(OTBS)2<br />

R′I<br />

(Me3Sn) 2<br />

TBS<br />

UV<br />

300 nm<br />

SILYLATION OF NITRO COMPOUNDS AS A PROCESS 695<br />

R<br />

496<br />

R′<br />

• TBSO•<br />

Me3SnI + Me3Sn• NOTBS<br />

R′<br />

TBSOSnMe3<br />

R3<br />

R<br />

R3<br />

R′ Yield 496<br />

%,%<br />

Yield 494<br />

%,%<br />

H<br />

Me<br />

n-C3H7 Ph<br />

CH2SO2Ph CH2SO2Ph CH2SO2Et CH2SO2Et 85<br />

71<br />

70<br />

82<br />

86<br />

91<br />

85<br />

93<br />

SPh<br />

CO 2Et<br />

Br<br />

SiMe2Bu t<br />

CH2SO 2Ph<br />

CH 2SO2Et<br />

CH2SO2Et<br />

CH 2SO 2Ph<br />

CH 2SO 2Et<br />

CH 2SO2Ph<br />

79<br />

72<br />

76<br />

79<br />

70<br />

Scheme 3.257<br />

1N HCl<br />

Hence, it is worthwhile to make an attempt to develop a convenient procedure<br />

for the synthesis of oximes (503) from available AN by rearrangements of the<br />

correspond<strong>in</strong>g BENAs.<br />

There are two ma<strong>in</strong> approaches to the generation of derivatives (504) from<br />

BENA (534) (Scheme 3.260).<br />

One approach is based on the reaction of BENAs with electrophiles E–X (path<br />

(a)) giv<strong>in</strong>g rise to cationic <strong>in</strong>termediates A, which react with the anionic <strong>in</strong>termediate<br />

[X–E–OSi] − without leav<strong>in</strong>g the cell. As a result, the OSi − fragment<br />

is “transferred” by the electrophile (LA) to the β-carbon atom to give bis-silyl<br />

derivative (504). If the OSi − anions leaves the cell, it can react with the start<strong>in</strong>g<br />

BENA as the nucleophile through the pathway (b) (see below).<br />

85<br />

73<br />

88<br />

93<br />

R<br />

O<br />

494<br />

R′

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