CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

• Shuxu Gao,
• Yu Liu and
• Shengming Ma

Beilstein J. Org. Chem. 2011, 7, 396–403, doi:10.3762/bjoc.7.51

• by Markó et al., the yields are relatively lower. Keywords: allenic ketone; allenol; Cu(I) catalyst; oxidation; Introduction The oxidation of alcohols is one of many fundamental reactions in organic synthesis [1][2]. Usually, stoichiometric oxidants such as MnO2 [3], PCC [4], PDC [4], etc. were

• of 1-naphthyl-substituted 1h afforded 2h in 74% yield (Table 5, entry 8). Tri-substituted allenic alcohol 1j was also oxidized to the corresponding allenic ketone 2j in 91% yield (Table 5, entry 10). The reaction may be easily carried out on a 1 g scale: the oxidation of allenol 1k afforded the

• corresponding allenic ketone 2k in 74% yield in 12 hours with just 10 mol % of CuCl and 5 mol % each of 1,10-phenanthroline and 2,2'-bipyridine (Scheme 1). When the reaction of 1-alkyl-substituted-2,3-allenols oxidation was conducted under 1 atm of oxygen at 60 °C, 81% of conversion was observed and the