College of Chemistry, Beijing Normal University, Beijing 100875, China.
J Org Chem. 2022 Aug 5;87(15):9576-9592. doi: 10.1021/acs.joc.2c00567. Epub 2022 Jul 12.
A simple and efficient two-step method for the construction of novel 2,4,9a-trisubstituted-4a,9a-dihydroindeno[2,1-][1,3]oxazin-9-ones has been developed. The NHC-catalyzed aza-benzoin reaction of -alkenyl benzaldehydes with -acylarylimines afforded 1-(-alkenylaryl)-2-amido-2-aryl-1-ethanones, which underwent regioselective 5-exo-trig radical cyclization to furnish the three-ring-fused heterocyclic products, generally in good yields. The synthetic method displayed good tolerance toward the nature of substituents, substitution pattern, and steric hindrance of -alkenyl benzaldehydes. Based on this method, the synthesis of unprecedented dihydrobenzo[6,7]indeno[2,1-][1,3]oxazin-7-ones and dihydropyrido[2',3':3,4]cyclopenta[1,2-][1,3]oxazin-9-ones has been achieved by employing -alkenylnaphthaldehyde and -alkenylnicotinaldehyde as substrates. The regioselectivity between 5- and 6- radical cyclization reactions of different 1-(-alkenylaryl)-2-amido-2-aryl-1-ethanones were elucidated with DFT calculations.
已开发出一种用于构建新型 2,4,9a-三取代-4a,9a-二氢茚并[2,1-][1,3]恶嗪-9-酮的简单高效两步法。NHC 催化的 -烯基苯甲醛与 -酰基芳基亚胺的氮杂苯偶姻反应得到 1-(-烯基芳基)-2-酰胺-2-芳基-1-乙酮，其经历区域选择性 5-exo-trig 自由基环化反应，以高收率得到三环稠合杂环产物。该合成方法对 -烯基苯甲醛的取代基性质、取代模式和空间位阻具有良好的耐受性。基于该方法，通过使用 -烯基萘甲醛和 -烯基烟醛作为底物，已经实现了前所未有的二氢苯并[6,7]茚并[2,1-][1,3]恶嗪-7-酮和二氢吡啶并[2',3':3,4]环戊并[1,2-][1,3]恶嗪-9-酮的合成。通过 DFT 计算阐明了不同 1-(-烯基芳基)-2-酰胺-2-芳基-1-乙酮的 5-和 6-自由基环化反应之间的区域选择性。
