Regioselective synthesis of 4- and 5-oxazole-phosphine oxides and -phosphonates from 2H-azirines and acyl chlorides |
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Authors: | Francisco Palacios Ana M Ochoa de Retana José I Gil José M Alonso |
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Institution: | Departamento de Química Orgánica I, Facultad de Farmacia, Universidad del País Vasco. Apartado 450, 01080 Vitoria, Spain |
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Abstract: | A simple and efficient regioselective synthesis of 4-oxazole-phosphine oxides 11 and -phosphonates 12 from 2H-azirine-phosphine oxides 1 and -phosphonates 6 is described. The key step for the synthesis of oxazoles 11 is a base-mediated ring closure of vinylogous α-aminophosphorus compounds derived from phosphine oxides 4 and from phosphonates 8. These derivatives 4 and 8 are obtained by reaction of functionalized azirines 1 and 6 with acyl chlorides 2 and subsequent acid-catalyzed ring opening of N-acylaziridine-phosphine oxides 3 and -phosphonates 7. Regioselective thermal ring cleavage of N-acylaziridine-phosphine oxides 3 leads α-chloro-β-(N-acylamido)-phosphine oxides 13 and their treatment with bases gives 5-oxazole-phosphine oxides 16. |
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Keywords: | Azirine phosphine oxide and phosphonate Oxazole Acyl chloride |
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