Effect of Water Molecules on the Cycloaromatization of Non-Conjugated Aromatic Tetraynes

Cycloaromatization of the thienyl tetrayne 1, which was prepared in several steps from bis(trimethylsilyl)butadiyne and 3-bromothiophene-2-carbaldehyde, in benzene (0.33 mM) in the presence of molecular sieves 3A at room temperature gave the indeno[2,1-b]thiophene ring-fused 1H-2-benzopyran derivative 10 and indeno[2,1-b]thiophene derivative 11 in 11 and 40% yields, respectively. In contrast, cycloaromatization of 1 in the presence of water molecules at room temperature gave the indeno[2,1-b]thiophene ring-fused 1H-2-benzopyran derivative 10 and the indene ring-fused indeno[2,1-b]thiophene derivative 12 in 82 and 14% yields, respectively. Cycloaromatization of the phenyl tetrayne 9 in the presence of water molecules at room temperature also resulted in a dramatic change in product yields.