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Unexpected reaction of 2-amino-1,4-naphthoquinone with aldehydes: new synthesis of naphtho[2,1-d]oxazole compounds

Author:
Van Aeken, Sam, Deblander, Jurgen, De Houwer, Johan, Mosselmans, Timothy, Abbaspour Tehrani, Kourosch
Source:
Tetrahedron 2011 v.67 no.2 pp. 512-517
ISSN:
0040-4020
Subject:
acetic acid, aldehydes, oxidation, synthesis
Abstract:
Treatment of 3-substituted 2-amino-1,4-naphthoquinones 3 with an aldehyde in a solution of hydrobromic acid in acetic acid led to 2,4-disubstituted naphtho[2,1-d]oxazol-5-ols. The outcome of this simple conversion is even more remarkable in view of the very similar reactions reported in literature, which all give rise to completely different products. Furthermore, the acquired naphthoxazoles 5–11 could be oxidatively ring opened by means of PIFA or CAN into a series of N-acylated 2-amino-1,4-naphthoquinones. A synthetic pathway towards 2-substituted naphtho[2,3-d]oxazole-4,9-diones was also disclosed as the outcome of CAN mediated oxidation of a 4-chloronaphtho[2,1-d]oxazol-5-ol.
Agid:
1093356