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

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

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18 NITRILE OXIDES<br />

obta<strong>in</strong>ed by the same authors, for nitrile oxides, cited above, <strong>and</strong> for benzonitrile<br />

oxide consider<strong>in</strong>g water as an O-nucleophile (122).<br />

S-Nucleophiles are very reactive <strong>in</strong> 1,3-addition reactions with nitrile oxides.<br />

A series of α-glucos<strong>in</strong>olates 27 (R = CR 1 =NOH; R 1 = Ph, CH2Ph, CH2CH2Ph,<br />

(E)-CH=CHPh, 3-<strong>in</strong>dolylmethyl) was prepared by addition reactions of thiol 27<br />

(R = H) with nitrile oxides (123). The <strong>in</strong>dolyl-substituted glucos<strong>in</strong>olate was then<br />

converted to α-glucobrassic<strong>in</strong> 28.<br />

AcO<br />

AcO<br />

CH2OAc O<br />

AcO<br />

SR<br />

27<br />

R = CR1 = NOH; R1 = Ph, CH2Ph, CH2CH2Ph, (E)-CH = CHPh, 3-<strong>in</strong>dolylmethyl<br />

HO HO<br />

CH2OH O<br />

HO<br />

SC ( = NOSO3K) CH2<br />

28<br />

Similarly, adducts 29 were prepared start<strong>in</strong>g from 2,3,4,6-tetra-O-acetyl-1-thioβ-D-glucopyranose<br />

(124).<br />

R1 AcO<br />

S<br />

O<br />

AcO<br />

29<br />

OAc<br />

CH2OAc <strong>Nitrile</strong> oxides were generated from oximes RCH:NOH by successive treatment<br />

with chlor<strong>in</strong>e <strong>and</strong> Et3N <strong>and</strong> used <strong>in</strong> situ without further puriÞcation. Only<br />

benzonitrile oxide <strong>and</strong> phenylacetonitrile oxide afforded normal adducts <strong>in</strong> high<br />

yields. The reactions generated from nitrile oxides with p-, m-, <strong>and</strong> o-methoxybenzaldehyde<br />

oximes gave adducts, chlor<strong>in</strong>ated <strong>in</strong> the benzene r<strong>in</strong>g, while the<br />

reactions with nitrile oxides, generated from p-chloro- <strong>and</strong> p-nitrobenzaldehyde<br />

oximes gave no adducts.<br />

Addition of C-nucleophiles to nitrile oxides is of special <strong>in</strong>terest. There are<br />

examples of reactions with both carbanions <strong>and</strong> neutral carbon nucleophiles. To<br />

the former group belong reactions of nitrile oxides with organometallic<br />

N<br />

H

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