在氧鎓离子参与的环化反应中，Prins型环化反应最具有代表性，近几年来取得了新的进展, 对多取代的二氢吡喃、四氢吡喃和哌啶环等的构建以及相关天然产物合成中显示出重要的应用价值。但是，产生启动该类反应的关键中间体氧鎓离子的方式比较有限，因而所得到的产物类型有一定的局限性。本项目拟通过Lewis酸等的作用，活化悬挂有烯键的醛羰基，并通过另一醛羰基或亚胺的作用，产生新型的氧（氮）鎓离子，发展新的Prins环化反应。通过在底物中引入不同的亲核性基团，建立结构复杂的含氧杂环、稠杂环、桥环缩醛类化合物的合成方法学，为桥环类具有1,3-二噁烷结构单元的天然产物、四氢化萘及类似物的合成，提供有效的合成策略。与此同时，结合计算化学方法，研究反应的机理、探索反应的规律。

Amongst the oxonium ion as well as oxocarbenium ion involved reactions, the Prins-type cyclization is the most representative one that has been proved to be one of the extremely powerful strategies for constructing dihydropyran (DHP), tetrahydropyran (THP) and piperidine rings as well as for the total synthesis of natural products containing such a heterocyclic core. However, as one of crucial point, the methods of generating the required oxonium ion intermediates are quite limited. In most cases, these are formed by action of homoallyic alcohols and an aldehyde promoted by Lewis acid or protonic acid, and therefore limiting the classes of products. In the present project, we will develop new Prins-type cyclizations. The strategy features the generation of the key oxonium ion or iminium ion intermediates by carbonyl-carbonyl dimerization or carbonyl-imine interaction under the promotion of various acidic species. It is envisioned that this oxocarbenium or related ions function as electrophiles, which can then be attacked by tethered internal olefin bond resulting in the formation of a more stable benzylic carbocation or related stable carcocation, which is simultaneously trapped by the oxy nucleophile or other external nucleophiles. The cascade reaction strategy will present a new method for oxa- or aza-heteocycles with variable complexity. Moreover, the methodology can find general application in the rapid synthesis of natural products bearing 1,3-dioxane subunit and tetrahydronaphthalene core structure of many naturally occurring, biologically active substances. Computations will also be performed to illuminate the mechanistic aspects.