Electrocyclic ring-opening/pi-allyl cation cyclization reaction sequences involving gem-dihalocyclopropanes as substrates: application to syntheses of (+/-)-, (+)-, and (-)-gamma-lycorane

Iodine(III)-mediated generation of nitrogen-tethered orthoquinol acetates for the construction of oxygenated indole, quinoline, and phenanthridine alkaloid motifs

Functionalized indole and quinoline derivatives are conveniently prepared from nitrogen-tethered 2-methoxyphenols via phenyliodine(III) diacetate mediated oxidative acetoxylation, followed by a fluoride- or base-induced intramolecular nucleophilic addition reaction. This regioselective Michael-type addition step is further discussed in view of the rearrangement of orthoquinol acetate intermediates into paraquinol acetates that is sometimes observed in situ. Application of this methodology to the synthesis of a functionalized phenanthridine, and its potential for the construction of polyoxygenated lycorine-type alkaloid skeleta are here described.