Hydroxylamine catalyzed Nazarov cyclizations of divinyl ketones
摘要:
The first examples of iminium catalyzed Nazarov cyclizations of divinyl ketones are presented. Experiments describing hydroxylamine catalysis of the cyclization of eight alpha-alkoxy divinyl ketones (60-79% yield) and one unactivated divinyl ketone (38% yield) are reported. Phenyl substitution at the beta-position of the divinyl ketone inhibits cyclization, whereas beta-alkyl substituted beta-alkoxy divinyl ketones readily cyclize. (C) 2015 Elsevier Ltd. All rights reserved.
Iodolium salts as halogen-bond donor catalysts in the Nazarov cyclization: the molecular oxygen enigma
作者:Avery J. To、Graham K. Murphy
DOI:10.1039/d2nj02731c
日期:——
Nazarov cyclizations of activated precurosrs are achieved under iodolium catalysis, provided that oxygen is present for catalyst activation and turnover.
An efficient metal-free catalytic protocol for the electrocyclization of alpha-alkoxydienones to cyclopentenones (Nazarov reaction) in near to quantitative yields is described. The key parameters are the use of inexpensive 4-toluenesulfonic acid in 5 mol % at room temperature in acetonitrile or under solvent-free conditions. The versatility of the transformation is demonstrated with unpolarized dienones with good regioselectivities and excellent yields. (c) 2008 Elsevier Ltd. All rights reserved.