Migration azido groups

Ring-chain tautomerism caused by the migration of an azido group has been observed rather rarely. By means of IR spectroscopy, the equilibrium 19A 19B was detected [81JCS(P1)2884] in benzene solutions of N,N-disubstituted tetrahalogenophthalamic acid azides. Mixtures of open-chain and cyclic isomers of 2-benzoylbenzoyl azide were obtained [88JCS(P1)2149], from which only isolation of the cyclic isomer succeeded. 

The procedure for the chlorosulfonation of azobenzene was first reported by PearP and was successfully repeated by Cremlyn. The comparatively drastic conditions required for the reaction 414— 415 (Equation 128) are probably due to initial protonation of the azido group in the strongly acidic medium. Attempts were made to extend the procedure to the chlorosulfonation of other azobenzenes. With 4-acetamidoazobenzene, extensive decomposition occurred at 125 °C, which may arise from acid-catalysed migration of the acetyl group into the aromatic nucleus, followed by decomposition of the resultant free amine intermediate. However, when the reaction temperature was reduced to 80 C, a low yield of the 4 -sulfonyl chloride was isolated. On the other hand, similar efforts to chlorosul-fonate p-(A iV-dimethylamino)azobenzene failed to yield a pure product,but more recently debsyl chloride 416 has been synthesized and is used as a derivatization reagent in HPLC for the separation of amines and amino acids. ... 

Carboxylic acids and esters can also be converted to amines with loss of the carbonyl group by reaction with hydrazoic acid, HN3, which is known as the Schmidt reaction,278 The mechanism is related to that of the Curtius reaction. An azido intermediate is generated by addition of hydrazoic acid to the carbonyl group. The migrating group retains its stereochemical configuration. 

A. Hasegawa, M. Goto, and M. Kiso, An unusual behavior Of methyl or benzyl 3-azido-5-0-benzoyl-3,6-dideoxy-a-L-talofuranoside with (dimethylamino) sulfur trifiuoride migration of the alkoxyl group from the C-l to the C-2 position, J. Carbohydr. Chem. 4 627 (1983). 

Evidence has been provided604 for intramolecular nucleophilic catalysis by the carbonyl group during methanolysis of o- and / -formylbenzenesulfonates in basic media (see Scheme 121). A theoretical study of the zwittazido cleavage of 4-azido-2-pyrrolinones has been undertaken,605 and ab initio calculations have been carried out to examine the possibility of the existence of a hexacoordinate phosphorus intermediate (469) in the migration reaction (468) —> (470) of dimethyloxyphosphorylthreonine.606... 

In the reaction of benzyl 3-azido-5-0-benzoyl-3,6-dideoxy-a-L-talofuranoside (4) with (diethylamino)sulfur trifluoride (DAST) the anomeric alkoxyl group migrated to the C-2 position and a fluorine atom entered into C-l from the P-side to give the 2-benzyl ether 5 having P-l-galacto configuration [101]. Methyl 2-0-benzoyl-5-0-... 

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