Enantioselective addition of nitrones to activated cyclopropanes.
In this paper, we demonstrate the first examples of chiral Lewis acid catalysis in the formation of tetrahydro-1,2-oxazines with very high enantioselectivity starting with diactivated cyclopropanes and nitrones (>90% yields and ee). Reactions with racemic substituted cyclopropanes provide approximately 1:1 diastereomeric tetrahydro-1,2-oxazine products with high enantioselectivity. Mechanistic information for the formation of the tetrahydro-1,2-oxazines is also detailed.
Sibi
Mukund P
MP
Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105, USA. Mukund.Sibi@ndsu.edu
Ma
Zhihua
Z
Jasperse
Craig P
CP
D003521:Cyclopropanes / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010078:Oxazines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D003521:Cyclopropanes; D009589:Nitrogen Oxides; D010078:Oxazines; C015388:nitrones