Lewis acid catalyzed benzannulation

邻炔(氧)苯1与炔2在(CH_2Cl)_2中催化反应，反应温度为80℃，高产率地得到了[4，2]苯环产物--萘酮衍生物3和4。用AuBr3代替AuCl3进行反应，加快了反应速度，提高了化学产率。另一方面，在催化剂铜(OTf)2和1当量的B酸(如CF_2HCO_2H)存在下，反应在100℃的(CH_2Cl)_2中进行，高产率地得到了脱羰基萘产品5。类似地，铜(OTf)_2-H_2O促进了烯醛6与炔2的反应，得到了相应的[4，2]苯环化产物--脱羰基苯衍生物7。Aux_&lt；3^-&gt；和Cu(OTf)_2催化的苯甲化反应很可能是通过生成苯并[c]吡咯酸盐络合物8、炔烃2与醋酸盐络合物的Diels-Alder加成以及生成的双环吡喃离子中间体9来进行的。有趣的是，烯醛6，包括邻炔基苯甲醛1，与羰基化合物10在100℃的1，4-二氧六环中，在AuBr3的催化下反应，得到了高产率的官能化芳香化合物3。AuBr3催化的[4 2]苯环化反应很可能是通过1到AuBr3的三键配位，通过羰基氧原子的亲核加成形成金酸吡喃配合物，由10衍生的烯醇的反向电子需求Diels-Alder加成，以及随后的脱水和键重排进行的。类似地，AuBr3催化1与缩醛化合物的反应以较高的产率得到相应的芳香族化合物。

The reaction of o-alkynyl(oxo)benzenes 1 with alkynes 2 in the presence of a catalytic amount of AuCl_3 in (CH_2Cl)_2 at 80℃ gave the [4+2] benzannulation products, naphthyl ketone derivatives 3 and 4, in high yields. When the reaction was carried out using AuBr_3 instead of AuCl_3, the reaction speed was enhanced and the chemical yield was increased. On the other hand, when the reaction was carried out in the presence of a catalytic amount of Cu(OTf)_2 and 1 equivalent of a Bronsted acid, such as CF_2HCO_2H, in (CH_2Cl)_2 at 100℃, the decarbonylated naphthalene products 5 were obtained in high yields. Similarly, the Cu(OTf)_2-H_2O promoted reaction of the enynals 6 with an alkyne 2 afforded the corresponding [4+2] benzannulation products, decarbonylated benzene derivatives 7, in good, yields. Both AuX_<3^-> and Cu(OTf)_2-catalyzed benzannulations proceed most probably through the formation of the benzo[c]pyrylium ate complex 8, the Diels-Alder addition of alkynes 2 to the ate complex, and the resulting bicyclic pyrylium ion intermediate 9. Interestingly, the reaction of enynals 6, including o-alkynylbenzaldehydes 1, and carbonyl compounds 10 in the presence of a catalytic amount of AuBr_3 in 1,4-dioxane at 100℃ gave the functionalized aromatic compounds 3 in high yields. The AuBr_3-catalyzed formal [4+2] benzannulation proceeds most probably through the coordination of the triple bond of 1 to AuBr_3, the formation of pyrylium auric ate complex via the nucleophilic addition of the carbonyl oxygen atom, the reverse electron demand type Diels-Alder addition of the enols, derived from 10, to the auric ate complex, and subsequent dehydration and bond rearrangement. Similarly, the AuBr_3-catalyzed reactions of 1 with acetal compounds afforded the corresponding aromatic compounds in good yields.