Yamazaki Shoko, Katayama Kohtaro, Wang Zhichao, Mikata Yuji, Morimoto Tsumoru, Ogawa Akiya
Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan.
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Nakaku, Sakai, Osaka 599-8531, Japan.
ACS Omega. 2021 Oct 18;6(42):28441-28454. doi: 10.1021/acsomega.1c05283. eCollection 2021 Oct 26.
Sequential Knoevenagel condensation/cyclization leading to indene and benzofulvene derivatives has been developed. The reaction of 2-(1-phenylvinyl)benzaldehyde with malonates gave benzylidene malonates, cyclized indenes, and dehydrogenated benzofulvenes. The product selectivity depends on the reaction conditions. The reaction with piperidine, AcOH in benzene at 80 °C for 1.5 h gave a benzylidene malonate in 75% yield as a major product. The reactions with piperidine, AcOH in benzene at 80 °C for 17 h and with TiCl-pyridine at room temperature gave an indene derivative in 56 and 79% yields, respectively, as a major product. The reaction with TiCl-EtN gave a benzofulvene in 40% yield selectively. Indene was transformed to a benzofulvene derivative using the reagents TiCl-EtN and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The reaction of variously substituted aryl derivatives with dimethyl malonate gave indene and benzofulvene derivatives. The reactions of 2-(1-phenylvinyl)benzaldehyde with Meldrum's acid or malononitrile also gave cyclized compounds in the suitable sequential or stepwise conditions. Furthermore, the reaction of 2-arylbenzaldehydes has been investigated. The limitation and scope have been described. The reaction mechanism of the cyclization steps has been examined by DFT calculations.
已开发出导致茚和苯并富烯衍生物的连续克脑文盖尔缩合/环化反应。2-(1-苯乙烯基)苯甲醛与丙二酸酯的反应生成亚苄基丙二酸酯、环化茚和脱氢苯并富烯。产物选择性取决于反应条件。在80℃下于苯中用哌啶、乙酸反应1.5小时，以75%的产率得到亚苄基丙二酸酯作为主要产物。在80℃下于苯中用哌啶、乙酸反应17小时以及在室温下用四氯化钛-吡啶反应，分别以56%和79%的产率得到茚衍生物作为主要产物。用四氯化钛-乙腈反应选择性地以40%的产率得到苯并富烯。使用四氯化钛-乙腈和2,3-二氯-5,6-二氰基-1,4-苯醌（DDQ）将茚转化为苯并富烯衍生物。各种取代的芳基衍生物与丙二酸二甲酯的反应生成茚和苯并富烯衍生物。2-(1-苯乙烯基)苯甲醛与麦氏酸或丙二腈的反应在合适的连续或分步条件下也得到环化化合物。此外，还研究了2-芳基苯甲醛的反应。描述了其局限性和范围。通过密度泛函理论计算研究了环化步骤的反应机理。
