Hydrogen Bonding Promotes 1-Butanol-3-Carbocation to 4-Methyl-1,3-Dioxane in Prins Condensation of Formaldehyde with Propene on Solid Acid Catalysts

Prins condensation provides an atom-efficient, clean route for the production of 1,3-diols, which is one class of important chemical intermediates. During the Prins condensation of formaldehyde with propene, the reaction involving the 1-butanol-3-carbocation determines the final products. Due to the hyperconjungation effect, 1-butanol-3-carbocation is highly reactive and easily deprotonates to form 3-buten-1-ol and its derivatives, and this significantly limits its electrophilic addition with formaldehyde to generate 4-methyl-1,3-dioxane, a precursor of 1,3-butanediol. Herein, we demonstrate a distinctive solvent effect on the pathway of Prins condensation of formaldehyde with propene on solid acid catalysts: Hydrogen bonding with water stabilizes 1-butanol-3-carbocation and weakens the hyperconjugation effect, which promotes electrophilic addition of 1-butanol-3-carbocation with formaldehyde to produce 4-methyl-1,3-dioxane. Selectivity of 4-methyl-1,3-dioxane was increased from 34.6% to 78.9% and 4-methyl-1,3-dioxane yield can be boosted up to 7.6-fold over Amberlyst-15 under optimized conditions when water was used as a cosolvent for Prins condensation of formaldehyde with propene. This work reveals the pivotal role of hydrogen bonds in directing the transformation pathways of Prins reaction and provides an efficient pathway for the production of 1,3-diols.