Conjugated 1,4-bis(nЈ-quinolyl)-1,3-butadiynes were obtained through the oxidative dimerization of the corresponding nЈ-ethynylquinolines catalyzed by cuprous chloride. Differential scanning calorimetry analysis of the 1,4-bis[nЈ-(quinolyl)]buta-1,3-diyne molecules produced evidence of a syn-anti rotational equilibrium around the 1,3-diyne axis and an irreversible transformation into a thermopolymer. The topooligomerization of 1,4-bis[3Ј-(quinolyl)]buta-1,3-diyne, which took place by irradiation with sunlight, was investigated with matrix-assisted laser desorption/ionization timeof-flight mass spectrometry. Accurate X-ray molecular structure and refinement analysis of 1,4-bis[3Ј-(quinolyl)]buta-1,3-diyne was conducted. The molecular crystalline packing consisted of parallel arrays of two groups of centrosymmetric molecules (antirotamer) in a herringbone assemblage in the solid state. The polymerization of 3-ethynylquinoline was carried out with the AlEt 3 /V(acac) 3 system to produce a mixture of 1,2,4-and 1,3,5-tris(3Ј-quinolyl)benzene cyclotrimers and a trans-cisoid polyene structure.
RESULTS AND DISCUSSION
Synthesis of n-Ethynylquinolines [2-Ethynylquinoline (1), 3-Ethynylquinoline (2), and 4-Ethynylquinoline (3)]1-3 were satisfactory obtained through the Sonogashira cross-coupling of an n-haloquinoline and 2-methyl-3-butyn-2-ol catalyzed by palladium. 11,12