Addition of hydrazoic acid to ketenes

Romero, ).A.C., and Fu, G.C. (2007) Enantioselective synthesis of protected amines by the catalytic asymmetric addition of hydrazoic acid to ketenes. Angew. Chem. Int. Ed., 46,4367-4369. 

And last, but not least, Fu et al. [21] reported that the planar-chiral heterocycle 45d catalyzed the enantioselective addition of hydrazoic acid to ketenes. This result in the formation of an acyl azide intermediate, which then can be subjected to Curtius rearrangement to supply a straightforward stereoselective access to chiral amines. As can be seen from Scheme 3.26, amine derivatives 56 were obtained in... 

Scheme 3.26 Enantioselective addition of hydrazoic acid to ketenes...

Scheme 3.27 Proposed catalytic pathway for the addition of hydrazoic acid to ketenes (Brdnsted acid/base catalysis)...

Fig. 36 Catalytic cycle for the Br0nsted-base catalyzed addition of phenols, hydrazoic acid, or 2-cyanopyirol to ketenes...

Addition of ketenes to imines addition of enamines to isocyanates 8-17 Reaction between cyclic ketones and hydrazoic acid (Schmidt)... 

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