A chalcone showing positional disorder, two related di­aryl­cyclo­hexenones showing enanti­omeric disorder and a related hy­dr­oxy­terphenyl, all derived from simple carbonyl precursors

Four compounds are reported, all of which lie along a versatile reaction pathway which leads from simple carbonyl compounds to terphenyls. (2E)-1-(2,4-Di­chloro­phen­yl)-3- [4-(prop-1-en-2-yl)phen­yl]prop-2-en-1-one, C18H14Cl2O, (I), prepared from 4-(prop-1-en-2-yl)benzaldehyde and 2,4-di­chloro­aceto­phenone, exhibits disorder over two sets of atomic sites having occupancies of 0.664 (6) and 0.336 (6). The related chalcone (2E)-3-(4-chloro­phen­yl)-1-(4-fluoro­phen­yl)prop-2-en-1-one reacts with acetone to produce (5RS)-3-(4-chloro­phen­yl)-5-[4-(propan-2-yl)phen­yl]cyclo­hex-2-en-1-one, C21H21ClO, (II), which exhibits enanti­omeric disorder with occupancies at the reference site of 0.662 (4) and 0.338 (4) for the (5R) and (5S) forms; the same chalcone reacts with methyl 3-oxo­butano­ate to give methyl (1RS,6SR)-4-(4-chloro­phen­yl)-6-[4-(propan-2-yl)phen­yl]-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate, C23H23ClO3, (III), where the reference site contains both (1R,6S) and (1S,6R) forms with occupancies of 0.923 (3) and 0.077 (3), respectively. Oxidation, using 2,3-di­chloro-5,6-di­cyano-1,4-benzo­quinone, of ethyl (1RS,6SR)-6-(4-bromo­phen­yl)-4-(4-fluoro­phen­yl)-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate, prepared in a similar manner to (II) and (III), produces ethyl 4′′-bromo-4-fluoro-5′-hy­droxy-1,1′:3′,1′′-terphenyl-4′-carboxyl­ate, C21H16BrFO3, (IV), which crystallizes with Z′ = 2 in the space group P[\overline{1}]. There are no significant inter­molecular inter­actions in the structures of compounds (I) and (II), but for the major disorder component of compound (III), the mol­ecules are linked into sheets by a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds. The two independent mol­ecules of com­pound (IV) form two different centrosymmetric dimers, one built from inversion-related pairs of C—H⋯O hydrogen bonds and the other from inversion-related pairs of C—H⋯π(arene) hydrogen bonds. Comparisons are made with related compounds