Publication Details (including relevant citation information):
Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999) (1994), (7), 865-73
Stereoselective isomerization of the pair of epimers rel-(2R,4S,5S)- and rel-(2S,4S,5S)-4-(4-isopropoxy-5,7-dimethoxynaphthalene-2-yl)-2,5-dimethyl dioxolane I with an excess of a mixt. of titanium tetrachloride and titanium tetraisopropoxide afforded the two products rel-(1R,3S,4S)-3,4-dihydro-4-hydroxy-6-isopropoxy-7,9-dimethoxy-1,3-dimethylnap htho[1,2-c]pyran II, and the C-1 epimer. Isomerization of rel-(2S,4R,5S)-4-(8-bromo-4-isopropoxy-5,7-dimethoxynaphthalen-2-yl)-2,5-dimeth yl dioxolane III with an excess of titanium tetrachloride alone afforded rel-(1S,3S,4R)-3,4-dihydro-4-hydroxy-6-isopropoxy-7,9-dimethoxy-1,3-dimethylnap htho[1,2-c]pyran IV and its 5-bromo derivs., the latter being formed through bromine migration on the arom. nucleus.
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