Stilbene, 3,3 -dimethoxy-4,4 -dihydroxy

The postulation that the structure of one dimer is 2,4 -dihydroxy-3,3 -dimethoxy-5-ethylbibenzyl is, of course, based on NMR data, on the proposal that phenylcoumarane structures are common in lignin [see (/)], and on evidence that they are cleaved to stilbenes by alkali (14) and eliminate 7-methylol units (2) as formaldehyde by mechanisms quite analogous to those above. Although there are some modest surprises in the structure of dimers isolated so far, it is gratifying how well these results fit into our long-standing concepts of lignin structure and reactions. 

S Ljunggren, E Johansson. The kinetics of hgnin reactions during oxygen bleaching. Part 2. The reactivity of 4,4 -dihydroxy-3,3 -dimethoxy-stilbene and (3-aryl ether structures. Nordic Pulp Pap Res / 5 148-154, 1990. 

Dimethoxytolane heated 10 hrs. at 90-95° with excess trimethylchlorosilane and excess magnesium in hexamethylphosphoramide -> 4,4 -dimethoxy-a,j -bis-(trimethylsilyl)stilbene (Y 71%) refluxed 12 hrs. with excess trimethyldiloro-silane in the presence of gallium chloride, excess trimethylchlorosilane removed by distillation, and the residue stirred 1 hr. with dil. HCl -> 4,4 -dihydroxy-a,j -bis(trimethylsilyl)stilbene (Y 82%). R. Calas and P. Bourgeois, C. r. 275 (C), 1117 (1972). 

Also obtained from 3,3 -dimethoxy-4,4 -dihydroxy-fran5-stilbene (27%) [6251]. 

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