Electrophilic carboxylation of alkenes
In the presence of 1.2 equivalents of boron trichloride 2,2-dichloro-1,3-benzodioxol (2) reacts with alkenes 4 to form 1:1 addition products 6, which are converted into the unsaturated tert-butyl esters 7 on treatment with potassium tert-butoxide. In the presence of ZnCl2, these reactions do not usually terminate at the 1:1-product stage, and 2,2-disubstituted 1,3-benzodioxols 5 are formed by reaction of 2 with two equivalents of 4a-f.