Lewis acid-mediated mono- and bis-addition of C-nucleophiles to 1,3-dioxolan-4-ones

The reactions of oxocarbenium cations with different types of C-nucleophiles is a convenient tool for building carbon-carbon bonds. Many examples of the generation of oxocarbenium cations from different types of five-, six-, and seven-membered ring acetals and related compounds have been reported. 1,3-Dioxolan-4-ones are readily available building blocks obtained by the condensation of carbonyl compounds with α-hydroxy carboxylic acids, including natural ones, such as malic, lactic, and mandelic acids. 1,3-Dioxolan-4-ones (the so-called Seebach chiral templates) have found widespread application in the preparation of chiral compounds. However, few examples of C-nucleophilic addition to the oxocarbenium cation generated from 1,3-dioxolan-4-ones under the action of Lewis acids are known. One of the most eco-friendly, lowest-cost, and most stable catalysts is FeCl₃, which exhibits a high activity in the reactions of acetals with allylsilanes and silyl ketene acetals. Therefore, we focused our attention on FeCl₃ when studying the reaction of 1,3-dioxolan-4-ones with different silicon-containing nucleophiles and 1-alkynes. We report examples of the Lewis acid-mediated reaction between 1,3-dioxolan-4-ones and C-nucleophilic reagents, which can result in either mono- and bis-addition depending on the nature of the nucleophile. For example, in the case of nucleophiles after addition of which a CH₂ unit or carbon-carbon triple bond forms near the cationic site, the reaction terminates at the step of mono-addition. In the case where an aromatic ring is adjacent to the cationic site, the addition of the second nucleophile molecule then occurs.