Waste-Free Catalytic Propargylation/Allenylation of Aryl and Heteroaryl Nucleophiles and Synthesis of Naphthopyrans
作者:J. McCubbin、Costa Nassar、Oleg Krokhin
DOI:10.1055/s-0030-1260146
日期:2011.10
pyrroles, as well as methoxy-substituted benzenes and naphthalenes. Reaction with 2-naphthol affords substituted naphthopyrans as products. Preliminary evidence suggests a Friedel-Crafts-like substitution mechanism, which occurs via an in situ generated carbocation. organocatalysis - boronic acids - propargylic alcohols - Friedel-Craftsreaction
cyclization between propargyl alcohols and ambident enols such as naphthols, 4-hydroxy coumarin, cyclohexane-1,3-dione, 5,5-dimethylcyclohexane-1,3-dione is described using Ca(OTf)2 under solvent free conditions. The reaction proceeds through a cascade annulation which involves an etherification, Claisen type rearrangement, allene formation and endocyclization. Further, we extended this method to the synthesis
1-(1H-inden-3-yl)naphthalen-2-ols. This intramolecular cycloetherification proceeds via C(sp2)–H oxygenation (C–H bond breaking and C–O bond forming), which enables the atom-economical synthesis of poly fused furans in high yields with large substrate diversity in the open air.