3,3,6,6-Tetramethoxy-1,2,4,5-tetramethyl-1,4-cyclohexadiene

Three tetramethylketals of 2,5-distyryl-[1,4]benzoquinones

“…2; 1---8 (C12---C13') distances 3.718 (2) in (I), 3.731 (4) A in (II)] generates a reduction of the angle O1--C3----O2 [99.2 (1) in (I), 99.3 (1) ° in (II)]. Similar molecular geometry was found in (V) (Norskov-Lauritsen et al, 1982). In the case of the gauche-anti conformation, however, this angle is not affected [106.1 (2) ° in (III)], as was also found for (IV) (Liebich et al, 1976).…”

Structures of 2-(3,5-dibromo-4-butoxy-1-hydroxy-4-methoxy-2,5-cyclohexadien-1-yl)ethanamide (I) and 2-(3,5-dibromo-1-hydroxy-4,4-dimethoxy-2,5-cyclohexadien-1-yl)ethanamide (II). Two marine compounds

“…Related literature. A similar anti-anti conformation of acetals in sterically hindered 1,4-cyclohexadiene rings has been reported by Norskov-Lauritsen, Larsen, Ettlinger & Jaroszewski (1982), versus the gauche-gauche conformation found in 3,3,6,6-tetramethoxy-l,4-cyclohexadiene (Liebich, Yvon & Margaretha, 1976). Compound (II) is also found in Verongia fistularis (Sharma, Vig & Burkholder, 1970).…”