1,3-dioxolan-2-ylium cations from acylfurans: Conversion of furyl ketones to esters under nonoxidative conditions

Article abstract of DOI:10.1016/S0040-4039(98)00185-3

Acylfurans 3 furnished tosylated glycol monoesters 5 when treated with 1,2-diols in the presence of an equivalent of TsOH. This process likely occurs via protiodefuranation of the intermediate furyl ketals to form 1,3- dioxolan-2-ylium cations 8. Subsequent ring-opening via S(N)2 nucleophilic displacement by p-toluenesulfonate then provides esters 5. When a 1,3-diol was employed, furancontaining ester 9 was formed instead of the standard product through an apparent aldol dimerization/fragmentation pathway.