Gothelf, K. V.; Torssell, K. B. G.
Acta Chem. Scand. 1994, 59, 165–168, doi: 10.3891/acta.chem.scand.48-0165
Department of Organic Chemistry, Chemical Institute, University of Aarhus, 8000 Aarhus C
4,6-Bis[3-(3,4,5-trimethoxyphenyl)isoxazol-5-yl]resorcinol 3 was generated in a Stille coupling between 4,6.diiodoresorcinol and 2 mol 5-tributylstannyl-3-(3,4,5.trimethoxyphenyl)isoxazole 2. 4-Iodoresorcinol was coupled with 3-phenyl-5-tributylstannylisoxazole to give 5-(2,4-dihydroxy-5-iodophenyl)-3-phenyl-isoxazole 8, which underwent Stille coupling with 2 to give 4-(3-phenylisoxazol-5-yl)-6-[3-(3,4,5-trimethoxyphenyl)isoxazol-5-yl]resorcinol 9. Reductive ring cleavage of 3 and 9 followed by acid catalysed cyclisation gave 2,8-bis(3,4,5-trimethoxyphenyl)pyrano[3,2-g]chromene-4,6-dione 4 and 2-phenyl-8-(3,4,5-trimethoxyphenyl)pyrano[3,2-g]chromene-4,6-dione 10, respectively, in fair overall yields.