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Paper | Special issue | Vol 67, No. 1, 2006, pp.247-254
Published online, 30th August, 2005
DOI: 10.3987/COM-05-S(T)22
Synthesis of 4H-3,1-Benzoxazines by the Reaction of o-(N-Acylamino)benzyl Alcohols with DAST

Takehiko Nishio,* Yukiko Kurokawa, Yoshiya Narasaki, and Tatsuhiro Tokunaga

*Department of Chemistry, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki 305-8571, Japan

Abstract

The treatment of o-(N-acylamino)benzyl alcohols (1) with DAST afforded the dehydrative cyclization product, 4H-3,1-benzoxazines (4) and the hydroxy replacement product, o-(N-acylamino)benzyl fluorides (5). The yields of benzoxazines (4) and fluorides (5) depend on the substituents at α-position and acyl groups. The treatment of α,α-diaryl-o-(N-acylamino)benzyl alcohols (1a-c) with DAST yielded benzoxazines (4a-c) exclusively, while that of α-monosubstituted o-(N-acylamino)benzyl alcohols (1d-k) with DAST yielded benzoxazines (4d-k) and fluorides (5d-k). In the reaction of o-(N-acylamino)benzyl alcohol (1l) with DAST, the formation of fluoride (5l) became predominant and that of benzoxazine (4l) was suppressed almost completely.