A pyrrolo[2,1-a]isoquinoline core structure is prevalent in marine and other natural products. This article describes a tungsten-catalyzed [3+2] cycloaddition aromatization of dihydroisoquinoline ester and maleic anhydride or an acrylate. The photochemical reaction tolerates a range of functional groups such as ester, cyano, ketone, bromide, and alkene. It is shown that the cycloaddition-aromatization of 2-substitued acrylate catalyzed by a tungsten photocatalyst can be used to evaluate the leaving ability of the leaving group. Experiments done to determine the reaction mechanism revealed that the formation of an ion-pair intermediate generated in situ from dihydroisoquinoline ester and (Z)-4-methoxy-4-oxobut-2-enoic acid via the solvolysis of maleic anhydride with methanol is crucial for the cascade process to occur. The key cycloadduct acid intermediate derived from [3+2] cycloaddition was isolated and determined by X-ray crystallography.

中文翻译：

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光诱导钨催化级联合成吡咯并[2,1-a]异喹啉-1,3-二羧酸酯及其反应机理

吡咯并[2,1- a ]异喹啉核心结构普遍存在于海洋和其他天然产物中。本文描述了二氢异喹啉酯和马来酸酐或丙烯酸酯的钨催化[3+2]环加成芳构化反应。光化学反应可耐受一系列官能团，如酯、氰基、酮、溴和烯烃。结果表明，钨光催化剂催化的2-取代丙烯酸酯的环加成-芳构化反应可用于评价离去基团的离去能力。确定反应机理的实验表明，通过马来酸酐与甲醇的溶剂分解，由二氢异喹啉酯和 ( Z )-4-甲氧基-4-氧代丁-2-烯酸原位生成离子对中间体的形成至关重要以便级联过程发生。分离并通过 X 射线晶体学测定了源自 [3+2] 环加成的关键环加合物酸中间体。