Boron trichloride has been found to be an efficient reagent for the selective cleavage of sterically hindered methoxy groups in methoxyarenes. The scope and utility of this reaction are explored with examples drawn from derivatives of benzene, naphthalene, 9,lO-dihydrophenanthrene and dibenzofuran. The method is applied to the synthesis of the phytoalexins a-(56) and 8-pyrufuran (58) (1,3,4-trimethoxydibenzofuran-2-01 and 1,2,4-trimethoxydibenzofuran-3-01). A synthesis of tri-0-methylleprolomin (61), a derivative of the unusual lichen metabolite leprolomin (60), is described and its demethylation with boron trichloride is studied. * A preliminary publication has appeared (ref.l).

The synthesis of the lichen dibenzofuran isodidymic acid (2)(3-hydroxy- 7-methoxy-9-pentyl-1-propyldibenzofuran-2-carboxylic acid) by intramolecular Ullmann coupling of methyl 3-iodo-4-(2′-iodo-5′-methoxy- 3′-pentylphenoxy)-6-methoxy-2-propylbenzoate (22), and further transformations, is described.

The crystal structure of the asymmetric 1,3-diol 1,1-diphenylbutane-1,3-diol has been determined and refined to a residual R of 0.039 for 795 observed reflections. Crystals are orthorhombic, space group P212121, with four molecules in a cell of dimensions a 9.625(4), b 16.002(3), c 8.834(3) Ǻ. The compound is unique among the known crystallographically characterized open-chain 1,3-diols in having only intramolecular hydrogen bonding involving the hydroxy groups [O-- -O 2.602(5) Ǻ].

The synthesis of 5-ethenyl-l-methyl-9,l0-dihydrophenanthrene-2,7-diol (effusol) (I), a natural product isolated from the marsh grass, Juncus effusus, is described. The key step was the intramolecular Ullmann reaction of methyl 2-bromo-3-[2'-(6-bromo-3"-methoxy-2-methylphenyl)ethyl]-5-methoxybenzoate (19).