Triphenylphosphine reduction of thiophene endoperoxides: Nucleophilic attack on sulfur versus biphilic insertion into the peroxide bond

Article abstract of DOI:10.1016/0040-4039(95)01553-1

The thiophene endoperoxide 2a, obtained by photooxygenation of thiophene 1a, led with triphenylphosphine to the furan 3a and betaine 4, while the 5-phenyl derivative 2b produced quantitatively furan 3b; two independent reaction pathways are proposed which entail nucleophilic attack on sulfur by triphenylphophine to afford entirone 5a and betaine 4 and biphilic insertion into the peroxide bond to generate furan 3a.