Au(I)-catalyzed intermolecular condensations between terminal alkynes and homopropargyl alcohols were reported as an effective strategy for the synthesis of hydrooxepine skeletons. It was found that only aliphatic terminal alkynes furnish the desired product in high yields (84%), in contrast to very low yields (<5%) with aromatic terminal alkynes. This work aims at understanding the different reactivities of aliphatic and aromatic terminal alkynes by performing DFT calculations. The results show that the reaction of the aliphatic terminal alkyne occurs via the intermolecular-addition-first mechanism, while that of the aromatic terminal alkyne proceeds via the intramolecular-cyclization-first mechanism. The overall barrier is 21.7 kcal/mol for the reaction of the former and 27.3 kcal/mol for that of the latter, rationalizing the experimental observation. The poorer reactivity of the aromatic terminal alkyne is attributed to the weaker electrophilicity of the proximal carbon in phenylacelene resulted from the conjugative effect between phenyl and alkynyl group.

据报道，Au（I）催化末端炔烃和高炔丙醇之间的分子间缩合是合成氢氧杂环丁烷骨架的有效策略。发现只有脂肪族末端炔烃以高产率（84％）提供所需产物，而芳族末端炔烃的产率很低（＜5％）。这项工作旨在通过执行DFT计算来了解脂族和芳族末端炔烃的不同反应性。结果表明，脂族末端炔的反应是通过分子间加成优先机制发生的，而芳族末端炔的反应是通过分子内环化优先机制发生的。前者的反应总势垒为21.7 kcal / mol，后者的总势垒为27.3 kcal / mol，合理化实验观察。芳族末端炔的较差反应性归因于苯基和炔基之间的共轭作用导致苯碳烯中近端碳的亲电性较弱。