260782-36-3Relevant articles and documents
A novel route to 5-substituted 3-isoxazolols. Cyclization of N,O-diBoc β-keto hydroxamic acids synthesized via acyl Meldrum's acids
Sorensen, Ulrik S.,Falch, Erik,Krogsgaard-Larsen, Povl
, p. 1003 - 1007 (2000)
3-Isoxazolols are most often synthesized from a β-keto ester and hydroxylamine. This cyclization typically gives rise to a major byproduct, the corresponding 5-isoxazolone. We have found that N,O-diBoc-protected β- keto hydroxamic acids can be synthesized and cyclized to 5-substituted 3- isoxazolols without formation of any byproduct. We present a novel and versatile three-step procedure in which carboxylic acid derivatives are converted into acyl Meldrum's acids which, upon aminolysis with N,O-bis(tert- butoxycarbonyl)hydroxylamine, lead to the N,O-diBoc-protected β-keto hydroxamic acids. These hydroxamic acid analogues were then, upon treatment with hydrochloric acid, cyclized to the corresponding 5-substituted 3- isoxazolols.