Asymmetric synthesis of 4-amino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans

Citation
A. Burgard et al., Asymmetric synthesis of 4-amino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans, TETRAHEDRON, 55(24), 1999, pp. 7555-7562
Citations number
12
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
TETRAHEDRON
ISSN journal
00404020 → ACNP
Volume
55
Issue
24
Year of publication
1999
Pages
7555 - 7562
Database
ISI
SICI code
0040-4020(19990611)55:24<7555:ASO4>2.0.ZU;2-4
Abstract
Highly enantioselective reduction of 3,4-dihydro-2,2-dimethyl-2H- 1 -benzop yran-4-ones 3 a-e by BH3 was achieved in the presence of catalytic amounts of Corey's oxazaborolidine 4 to afford the corresponding 3,4-dihydro-2,2-di methyl-2H-1-benzopyran-4-ols 2a-e in quantitative yields. These benzopyran- 4-ols 2a-e were converted into the chiral 4-amino-3,4-dihydro-2,2-dimethyl- 2H-1-benzopyran 1a-e by mesylation, followed by introduction of an azide gr oup by tetra-n-butyl-ammonium azide, and finally by reduction of the azide 6 with triphenylphosphine under very mild conditions without loss of stereo information. (C) 1999 Elsevier Science Ltd. All rights reserved.