Oximino azides—

Curtius rearrangement of a-oximino acid azides is reported as a new method of synthesis for 3-substituted 5-hydroxyoxadiazoles. In this method, the oxime of an a-ketoester is converted to the acid hydrazide, which in turn is converted to the azide by reaction with nitrous acid 115a). 

Curtius rearrangement of a-oximino acid azides 115a) (see p. 817). 

LVI) was proved 54) by Esohweiler-Clarke methylation to methyl-holaphylline and was further confirmed by a synthesis from pregnenolone (LIX) via 3 8-tosyloxy-20-oximinopregn-5-ene (LX) which on treatment with sodium azide in methanol yielded a mixture of 3 3-azido-20-oximino-pregn-5-ene (LXI) and the 3a,6a-cyclo-6 -azido isomer. Selective reduction with lithium aluminum hydride followed by acid hydrolysis yielded holaphyllamine along w ith its 3,5-cyclo isomer which could be separated by chromatography (55). 

Bromo-5-imino-3-pyrazolidinones are synthesized by Curtius rearrangement of the azides of 4-bromo-5-oxo-3-pyrazolin-3-carboxylic acids.697 4-Nitroso-5-imino-3-pyrazolidinones are believed to exist as the oximino tautomers.337 They are usually prepared by direct nitro-sation with nitrous acid.644-1339 1649 A Curtius rearrangement of 4-oximino-5-oxo-2-pyrazolin-3-carboxylic acid azide has also been used.337... 

This reaction is called diazo transfer. Various arenesulfonyl azides and methanesul-fonyl azide are used most frequently, a-Diazoketones can also be made by first converting the ketone to an a-oximino derivative by nitrosation and then allowing the oximinoketone to react with chloramine. ... 

The 2-acetoxyimino-2-deoxy- glycosyl azide 62 was obtained from the corresponding a-chloride (by reaction with NaNj, CH3CN), and converted into the (V-(2-deoxy-2-oximino-p-gIycosyI)-acetamide 63 in low yield on hydrogenation (Scheme 4). 0- N Acetyl migration was a... 

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