A short, efficient synthesis of the lignan (+)-lyoniresinol dimethyl ether is described. The synthesis is achieved by asymmetric photocyclization of an achiral dibenzylidenesuccinate to a chiral aryldihydronaphthalene. (-)-Ephedrine is used as a chiral auxiliary to bias the atropisomeric equilibrium in the dibenzylidenesuccinate prior to the photochemical reaction. The synthesis of the title compound was accomplished in five steps, and the final product was recrystallized to constant melting point and rotation.

The title compound, C12H20N2S4, synthesized by the reaction of 2,3,5,6-tetra­kis­(bromo­meth­yl)pyrazine with sodium methane­thiol­ate, crystallizes with a half -mol­ecule in the asymmetric unit. The whole mol­ecule is generated by inversion symmetry; the inversion centre being located in the centre of the pyrazine ring. The mol­ecule has an S-shaped conformation with two (methyl­sulfan­yl)methyl substituent arms directed above the plane of the pyrazine ring and two below. The C(H3)—S—C(H2)—C(aromatic) torsion angles are 70.47 (18) and −67.65 (17)°, respectively. In the crystal, mol­ecules are linked via weak C—H⋯S hydrogen bonds, forming chains along [001] and enclosing R 2 2(12) ring motifs. The chains are linked by further weak C—H⋯S hydrogen bonds, forming sheets lying parallel to (101).

The structure of trans‐[Ni(CH3CN)2(H2O)4]Br2 has been determined at 153 K. The complex possesses Ci symmetry, with the NiII atom lying on an inversion center. The Ni atom is coordinated to four water mol­ecules in the equatorial plane and to two trans aceto­nitrile mol­ecules. In the crystal, a three‐dimensional structure is formed by hydrogen bonding involving the lattice Br− ions and the coordinated water mol­ecules.

The title compounds, C(32)H(28)N(2)O(4), (I), and C(32)H(28)N(2)S(4), (II), respectively, are tetrasubstituted pyrazines and both possess C(i) symmetry. They differ only in the hetero atom (X) of the -CH(2)XPh side-arm substituents: X = O in (I) and S in (II). Compound (I) has an overall S-shape with a pair of adjacent -CH(2)OPh side arms alternately above and below the plane of the central pyrazine ring. The phenyl rings are inclined to one another by 12.63 (18) degrees and there is one intramolecular C-H...O hydrogen bond involving adjacent -CH(2)OPh side arms. In compound (II), adjacent -CH(2)SPh side arms point in opposite directions with respect to the pyrazine ring plane, with the phenyl rings inclined at 60.45 (8) degrees. Both structures have weak C-H...pi intermolecular interactions.

The photochemistry of diethyl E,E-2,3-(3,4,5-trimethoxybenzylidene)succinate (8) is solvent dependent. In both protic and aprotic solvents, there is a photoequilibrium established between 8 and its E,Z-isomer (9). In chloroform at high light intensity, very little 9 is formed and the main product is 1,4-dihydronaphthalene (10), formed via photoinduced intramolecular [1,3]-sigmatropic hydrogen shift within an intermediate 1,8a-dihydronaphthalene (11). In protic solvents, irradiation of either 8 or 9 ultimately gives primarily the cis-1,2-dihydronaphthalene product (13), along with smaller amounts of the trans isomer (14). By using deuterated solvents, it was shown that 13 and 14 are formed by solvent protonation (or deuteration) of the 1,8a-dihydronaphthalene intermediate (11 or 12). Key words: 2,3-dibenzylidenesuccinate, photocyclization, dihydronaphthalene, lignan.