Difluoroenoxysilane, a commonly used difluoroallylating reagent, has attracted considerable attention in recent years. However, its application in the annulation reaction for the construction of fluorinated heterocyclic compounds remains relatively limited. Presented here is the Brønsted acid-catalyzed efficient formal [4 + 2] annulation of difluoroenoxysilanes with α-cyano chalcones. The developed protocol demonstrates tolerance to various substituents under mild reaction conditions, providing a reliable approach to construct gem-difluoro-3,4-dihydro-2H-pyrans in good to excellent yields with high diastereoselectivities.

中文翻译：

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通过 TfOH 催化的二氟烯氧基硅烷与 α-氰基查尔酮的 [4 + 2] 环化反应合成偕二氟-3,4-二氢-2H-吡喃

二氟烯氧基硅烷是一种常用的二氟烯氧基化试剂，近年来引起了人们的广泛关注。然而，其在构建氟化杂环化合物的成环反应中的应用仍然相对有限。这里介绍的是二氟烯氧基硅烷与 α-氰基查耳酮在布朗斯台德酸催化下的高效形式 [4 + 2] 成环反应。所开发的方案证明了在温和反应条件下对各种取代基的耐受性，提供了一种可靠的方法来构建宝石-二氟-3,4-二氢-2 H-吡喃，以良好至优异的产率和高非对映选择性。