Interaction of N,N-dimethylhydrazonomethyl and α-hydroxyketone groups in hetaryl analogs of unsymmetrical benzoins

The reaction of phenylglyoxal hydrate with N,N-dimethylhydrazones of furfural and 1-methylpyrrole-2-carbaldehyde proceeds regioselectively at position 5 of the heterocycle. The hetaryl analogs of α-benzoins obtained are quantitatively isomerized into the isomeric β-benzoins. The N,N-dimethylhydrazonomethyl group, while activating the hetaryl residue, reduces the time for isomerization compared with unfunctionalized benzoins. The N, N-dimethylhydrazonomethyl group is readily transformed into an aldehyde or nitrile group and enters into a trans-hydrazonation reaction. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1805–1814, December, 2005.