5,8-Dihydronaphthalene-1,4-diol,
readily available from benzoquinone and buta-1,3-diene, is isomerized
by heating with strong sodium hydroxide, and acetylated (Ac2O), in situ, to form 5,8-diacetoxy-1,2-dihydronaphthalene.
Catalysed (AlCl3) addition of acetyl chloride followed by dehydrochlorination (LiCI/HCONMe2) yielded
5,8-diacetoxy-3-acetyl-1,2-dihydronaphthalene (11) in 82% overall yield. Base
hydrolysis of (11), followed by methylation (Me2SO4)
gives 3-acetyl-5,8-dimethoxy-1,2-dihydronaphthalene in 94% yield, the most
direct route to this product so far described. More importantly, the diacetate (11) is selectively deacetylated
at C5 (Cs2CO3 in tetrahydrofuran, or K2CO3
in Me2SO) to form the related phenol, alkylation
of which produces the 5-alkoxy compound. Further hydrolysis followed
by alkylation yields the unsymmetrically,
but regiospecifically substituted, 3-acetyl-5,8-dialkoxy-1,2-dihydronaphthalenes.
This method is specifically illustrated by the production of
3-acetyl-5-benzyloxy-8-methoxy-1,2-dihydronaphthalene which is formed in a
short, cost effective synthesis in a moderate overall yield (25%) based upon
benzoquinone as starting material;significantly, no
chromatographic separations are required.
Cell-free protein synthesis and in situ immobilization of deGFP-MatB in polymer microgels for malonate-to-malonyl CoA conversion