Copper-mediated oxygenation of aldehydes and internal Cannizzaro-like rearrangement of phenylglyoxal

1990 
Under the influence of Cu(II) in MeOH containing py and Et 3 N, PhCH 2 CHO undergoes competitive O 2 -dependent conversions to PhCHO and phenylglyoxal. The latter, as the MeOH hemiacetal, undergoes a Cu-(II)-catalyzed rearrangement to PhCHOHCOOMe and a Cu(II) oxidation to PhCOCOOMe, and there appears to be an independent O 2 -mediated production of PhCOCOOH. Phenylglyoxal also undergoes oxidative cleavage to PhCOOH, but does not give rise to PhCHO. Product comparisons using either an O 2 atmosphere or a N 2 atmosphere (with varying equivalents of Cu II ) permit a distinction between stoichiometric Cu(II) oxidations and O 2 -dependent reactions. Mechanisms are proposed for the observed transformations
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