Cycloadditions. 26. Influence of Substituents in the Allenic ω-Position on the Thermal Behaviour of Aryl Allenecarboxylates

Article abstract of DOI:10.1002/prac.19973390142

The [(aryloxycarbonyl)methyl]triphenylphosphonium salts (1a and i), obtained by reaction of aryl bromoacetates with triphenylphophine, react with the acid chlorides 3 in the presence of two equivalents of triethylamine to give the phenyl- or the (1-naphthyl)-2,3-alkadienoates (4a-d and 4e-h), respectively, in the most cases accompanied by the aryl alkynoates 6 and 7 and/or with the naphthyl esters 8 of the used acids. Treatment of the f(aryloxycarbonyl)methyl]triphenylphosphonium salts (1a-i) with triethylamine furnishes the phosphoranes 2a-i, which are transformed by reaction with diphenylketene into the aryl 3,3-diphenyl-2,3-butadienoates (5). Heating of the derivatives 4a-d and 5a, bearing the unsubstituted phenyl nucleus in the ester moiety, leads to destruction, while heating of the naphthyl esters 4e-h and 5i - room temperature is sufficient in some cases - induces the IMDA-reaction to give the benzo-tricycles 9a-e. Heating of the 4,4-diphenyl-2,3-butadienoates (5b-h), bearing the alkylsubstituted phenyl ring within the ester component, induces radical dimerization to give the cylobutanes 10b-h, which represent the head to tail dimers.