A highly stereoselective approach to the synthesis of functionalized pyranderivatives by Lewis acid assisted fetal reduction and allylation

Authors
Bogaczyk, S Brescia, MR Shimshock, YC DeShong, P
Citation
S. Bogaczyk et al., A highly stereoselective approach to the synthesis of functionalized pyranderivatives by Lewis acid assisted fetal reduction and allylation, J ORG CHEM, 66(12), 2001, pp. 4352-4355
Citations number
29
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
JOURNAL OF ORGANIC CHEMISTRY
ISSN journal
00223263 → ACNP
Volume
66
Issue
12
Year of publication
2001
Pages
4352 - 4355
Database
ISI
SICI code
0022-3263(20010615)66:12<4352:AHSATT>2.0.ZU;2-J
Abstract
Reduction of bicyclic ketal 1 gave functionalized pyran derivatives 7a or 7 b in a highly stereoselective manner, depending upon the reduction conditio ns utilized. For example, treatment of ketal 1 with TiCl4/Et3SiH produced e xclusively diol 7b with the 2,5-syn relationship in good yield. Alternative ly, reduction of ketal 1 by DIBALH gave 2,5-anti-diol 7a stereoselectively. Alane reductions of ketal 1 were highly stereoselective also; however, the syn/anti selectivity observed was strongly dependent an the ratio of reage nts employed for in situ generation of the alane. Lewis acid catalyzed ally lation of ketal 1 gave pyran 10 in a stereospecific alkylation reaction.