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A Route to Carbasugar Analogues - Jonathan Clayden - The ...

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3.2 – Oxazoline removal<br />

3.2.3 Reduction of oxazolines<br />

3.2.3.a Catalytic hydrogenolysis<br />

O NH 2<br />

Ph Ph<br />

O N<br />

c-Hex<br />

101m<br />

H 2 , Cat.<br />

HO N<br />

c-Hex Ph<br />

202<br />

Ph<br />

H 2 , cat.<br />

±H<br />

O<br />

c-Hex<br />

203<br />

H<br />

N<br />

H 2 , cat.<br />

Ph<br />

c-Hex<br />

Ph<br />

204<br />

Scheme 3.24 – hydrogenolysis of oxazolines<br />

Whilst the hydrogenolysis of an oxazoline containing a benzylic C–O bond is known<br />

(section 3.2.1.c), diphenyl oxazoline 101m also contains the much stronger C–N bond.<br />

It was unclear how labile this aza-allylic bond would be, but amine N-benzyl bonds are<br />

often resistant <strong>to</strong> hydrogenolysis, whilst those of amides such as 204 are no<strong>to</strong>riously<br />

resistant. 117<br />

114

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