The iodine-catalyzed Prins cyclization of homoallylic alcohols and aldehydes was investigated under metal-free conditions and without additives. Anhydrous conditions and inert atmosphere are not required. The reaction of 2-(3,4-dihydronaphthalen-1-yl)propan-1-ol and 21 aldehydes (aliphatic and aromatic) in CH2Cl2 in the presence of 5 mol % of iodine gave 1,4,5,6-tetrahydro-2H-benzo[f]isochromenes in 54%–86% yield. Under similar conditions, the Prins cyclization of six alcohols containing an endocyclic double bond (primary, secondary, or tertiary) led to dihydropyrans in 52%–91% yield. The acyclic homoallylic alcohols gave 4-iodo-tetrahydropyran in 29%–41% yield in the presence of 50 mol % of iodine. This type of substrate is the main limitation of the methodology. The relative configuration of the products was assigned by NMR and X-ray analysis. The mechanism and the ratio of the products are discussed, based on DFT calculations.
在无
金属和无添加剂的条件下研究了
碘催化的高
烯丙醇和醛的 Prins 环化。不需要无
水条件和惰性气氛。 2-(3,4-二氢
萘-1-基)丙-1-醇和 21 种醛(脂肪族和芳香族)在
CH2Cl2 中在 5 mol%
碘存在下反应,得到 1,4,5,6-四氢-2H-苯并[f]异色烯,产率 54%–86%。在类似条件下,六种含有环内双键(伯键、仲键或叔键)的醇进行 Prins 环化,生成二氢
吡喃,产率为 52%–91%。在 50 mol % 的
碘存在下,无环高
烯丙醇以 29%–41% 的产率生成 4-
碘-
四氢吡喃。这种类型的底物是该方法的主要限制。通过NMR和X射线分析确定了产物的相对构型。基于DFT计算,讨论了机理和产物的比例。