Synthesis and Crystal Structure of trans-3-(4-Acetoxy-3-methoxyphenyl)-8-acetyloxy-2-methyl-2,3-dihydro-1,4-benzodioxine.

A synthesis of the neolignan model compound 3-(4-hydroxy-3-methoxyphenyl )-8-hydroxy-2-methyl-2,3-dihydro-1,4-benzodioxine (3A) was achieved with high stereo- and regio-selectivity by oxidative coupling of phenols in the presence of Ag2O. The regiochemical assignments at C-8 were derived from a crystal structure determination by single-crystal X-ray diffraction analysis of diacetate 5A, which could not be established unambiguously by NMR spectroscopy. Compound 5A crystallizes as colourless prisms in the monoclinic space group P2(1)/a with a = 11.524(2), b = 11.959(2), c = 14.284(1) Angstrom, alpha = 90 degrees, beta = 109.14(1), gamma = 90 degrees, V = 1860.3(5) Angstrom(3) and Z = 4. A final R-value of 0.059 was obtained.