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Lewis acid catalyzed benzannulation

路易斯酸催化苯并环化

基本信息

批准号：
15350052
负责人：
ASAO Naoki
金额：
$ 9.73万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15350052/
关键词：
Lewis acid benzannulation benzo[c]pyrylium ate complex Diels-Alder reaction retro-Diels-Alder reaction enol form gold catalyst copper catalyst

项目摘要

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.

邻炔（氧）苯1与炔2在催化量AuCl_3存在下于（CH_2Cl）_2中于80℃反应，高产率地得到[4+2]苯环化产物萘酮衍生物3和4。当用AuBr_3代替AuCl_3进行反应时，反应速度加快，化学产率提高。另一方面，在催化量的Cu（OTf）_2和1当量的Bronsted酸（如CF_2HCO_2H）存在下，在（CH_2Cl）_2中于100℃进行反应时，可高产率地得到萘的脱羰基产物5。同样，在Cu（OTf）_2-H_2O催化下烯炔醛6与炔2反应，得到相应的[4+2]苯环化产物脱羰基苯衍生物7。AuX_（3^-）和Cu（OTf）_2催化的苯并环化反应都很可能通过形成苯并[c]吡喃鎓酸盐配合物8、炔2与酸盐配合物的Diels-Alder加成反应以及得到的双环吡喃鎓离子中间体9来进行。有趣的是，烯醛6（包括邻炔基苯甲醛1）与羰基化合物10在催化量的AuBr_3存在下于1，4-二氧六环中于100℃反应，高产率地得到了官能化的芳香化合物3。AuBr_3催化的缩甲醛[4+2]苯并环化反应可能是通过1与AuBr_3的三键配位、羰基氧原子的亲核加成形成吡喃金酸盐配合物、10衍生的烯醇与金酸盐配合物的反电子需求型Diels-Alder加成以及随后的脱水和键重排进行的。类似地，1与缩醛化合物在AuBr_3催化下的反应以良好的产率得到相应的芳香化合物。