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The role of the oxygen atom in benzylic hydroxylations of naphthopyrans
Journal article   Open access   Peer reviewed

The role of the oxygen atom in benzylic hydroxylations of naphthopyrans

R.G.F. Giles and I.R. Green
South African Journal of Chemistry, Vol.43(3-4), pp.96-100
1990
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Abstract

Benzylic hydroxylation of 5,1 0-dimethoxy-2,2-dimethylnaphtho[2,3-bj pyran followed by oxidative demethylation afforded the naturally occurring 4-hydroxy-a-lapachone as its racemate, in 72% yield. Treatment of trans-1 ,2,3,4-tetrahydro-5, 1 0-dimethoxy-1 ,3-dimethylanthracene under similar conditions failed to hydroxylate the 4-position. It would thus appear that the naphthopyran ring-oxygen facilitates benzylic hydroxylations at C(4) in both naphtho[2,3-bj- and naphtho[2,3-cJpyrans.

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