Revision of the structure and stereochemistry of the 2-naphthol-acetaldehyde 2 : 2 condensation product. A study by X-ray crystallography and the AM1method

The structure of the 2:2 condensation product of 2-naphthol and acetaldehyd e, 1-(1-methyl-2,3-dihydro-1H-benzo[f]chromen-3-yl)-2-naphthol, revised by X-ray crystallography, is presented. A moderate intramolecular hydrogen bon d is found between the phenolic OH and chromene oxygen atom both in the sol id state and in solution. In the crystal structure, the naphthyl groups are oriented in parallel with a pi-pi stacking distance of 354 pm. AM1 studies are used to explain the formation of one of the four possible stereoisomer s for the title compound. Comparison of the experimental and calculated cou pling constants indicates that the molecule adopts exclusively the solid-st ate structure in solution. Copyright (C) 2001 John Wiley & Sons, Ltd.