Bergman Cyclization of Fluorinated Benzo-Fused Enediynes to Naphthalene Derivatives: Syntheses and Structures

An exceptional 5:4 enantiomeric structure

The only crystals that could be grown from racemic solutions of the PF6−salt of the resolvable cation [Ru(2,9-dimethyl-1,10-phenanthroline)2(dipyrido[3,2-d:2′,3′-f]quinoxaline)]2+have translational symmetry only (space groupP1), contain nine independent sets of ions, and include numerous independent solvent molecules (11 acetone, one diethyl ether and possibly several water molecules). Layers of hydrophobic cations alternate with layers containing most of the anions and solvent molecules. All nine cations have the same basic conformation, which is distorted by the presence of the methyl substituents on the two 1,10-phenanthroline ligands. Four pairs of enantiomeric cations within a layer are related by approximate inversion centers; the ninth cation, which shows no sign of disorder, makes the layer chiral. Within the cation layers stripes parallel to [110] of six cations alternate with stripes of three; the local symmetry and the cation orientations are different in the two stripes. These stripes are reflected in the organization of the anion/solvent layer. Theca80:20 inversion twinning found indicates that enantiomeric preference is transmitted less perfectly across the anion/solvent layer than within the cation layer. The structure is exceptional in having nine independent formula units and an unbalanced set (ratio 4:5) of resolvable enantiomers. The difficulty in growing crystals of this material is consistent with its structural complexity.

(Hetero)aromatics from dienynes, enediynes and enyne–allenes

Recent advances in the synthesis of (hetero)aromatics starting from polyenes, such as dienynes, enediynes and enyne–allenes, are discussed.

CuO/I2-mediated intramolecular annulation for the synthesis of 2-aroyl-3-hydroxy-4-iodonaphthalenes

A novel method for the direct synthesis of 2-aroyl-3-hydroxy-4-iodonaphthalenes has been developed via CuO/I₂-mediated domino reactions.

4,4'-(4,5-dimethyl-1,2-phenylene)bis(2-methylbut-3-yn-2-ol): structural variation in vicinal dialkynols

The structure of the title compound, C(18)H(22)O(2), contains two non-equivalent molecules which differ primarily in the location of the -OH groups on opposite sides or on the same side of the molecular plane. Inversion-symmetric pairs of molecules form intermolecular O-H...O hydrogen-bonded tetrameric synthons that link non-equivalent molecules into an approximately square double layer parallel to (-102). Recently reported fluorinated analogues [Kane, Meyers, Yu, Gerken & Etzkorn (2011). Eur. J. Org. Chem. pp. 2969-2980] have significantly different structures of varying complexity that incorporate intramolecular hydrogen bonding and suggest that further study of structure versus substituents in vicinal dialkynols could be fruitful.