Selwyn Yorke - The stereoselective formation of naphtho[1,2-c]pyrans, angular analogs of the aphin-derived glucoside B, by an intramolecular version of the Mukaiyama reaction of 4-naphthyldioxolanes

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      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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