期刊
TETRAHEDRON
卷 69, 期 6, 页码 1705-1711出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2012.12.031
关键词
Quinazoline; NMR; O-alkylation; N3-alkylation
资金
- Czech Science Foundation [P207/10/2048]
- Charles University in Prague [SVV-265-001]
Contrary to a number of reports, alkylations of the privileged 3,4-dihydroquinazoline scaffold provide N3-alkylated products, and not 4-alkoxyquinazolines. To correctly assign the structure, C-13 NMR shifts of the -Z-CHn- (Z=O, N) fragment are necessary; resonances in the 45-55 ppm range are indicative of N3-allcylation. Treatment of 3,4-dihydroquinazoline-4-one with p-TsCl afforded the N3-tosylated compound, whose reaction with an amine yielded the corresponding N3-alkyl derivative. A mechanism corroborated by N-15-labeling involving pyrimidine ring opening and recyclisation is proposed. Finally, the unambiguous preparation of 4-alkoxyquinazolines is described via treatment of 3,4-dihydroquinazoline-4-ones with PCl5 followed by an alkoxide. (C) 2012 Elsevier Ltd. All rights reserved.
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