Stereochemistry of the products from the alkylation of 2-naphthol with glyoxal

Structural analyses of the products formed in the base-catalysed alkylation of 2-naphthol with glyoxal were performed by IR, 1H and 13C NMR spectroscopy and mass spectrometry. The final product, 7a,14c-dihydrobenzo[e]benzo[4,5]benzofuro[2,3-b]benzofuran (4), was determined to be in the cis rather than the trans form. MO calculations of the heats of formation and geometrical parameters also favour the cis form for 4. Two precursors of 4, 1,2-dihydronaphtho[2,1-b]furan-1,2-diol and 1-(2-hydroxy-1-naphthyl)naphtho[2,1-b]furan-2-ol, have also been analysed and their stereochemistry is discussed.