Pyridinium Ion Catalysis of Carbonyl Protection Reactions

[摘要]：Aprotic pyridinium ions incorporating electron-withdrawing substituents on the aromatic ring are powerful catalysts for the acetalization of aldehydes and the formation of dithianes, dithiolanes, dioxanes, and dioxolanes. Under optimum conditions the best catalyst can be used at a loading as low as 0.1 mol% and can outperform a Bronsted acid catalyst with a pK(a) of 2.2.

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