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.
2-Alkoxyarenol-derived orthoquinols in carbon-oxygen, carbon-nitrogen and carbon-carbon bond-forming reactions
Silylated oxygen- and nitrogen-tethered orthoquinol acetates, generated by phenyliodine(III) diacetoxy-mediated oxidative acetoxylation of 2-alkoxyphenols in CH2Cl2 can be used to furnish regioselectively benzannulated heterocycles. Oxidative activation of 2-alkoxynaphthols with non-nucleophilic phenyliodine(III) bis(trifluoroacetoxy) in the presence of carbon nucleophiles, including oxidation sensitive silyl enol ethers, constitute a potentially valuable route to naturally occurring vicinally oxygenated benz[a]anthracene motifs.
Quideau, Stéphane,Pouységu, Laurent,Oxoby, Mayalen,Looney, Matthew A
p. 319 - 329
(2007/10/03)
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