1,4-Addition of Ozone to Furans and Pyrroles

Reactions of pyrrole, imidazole, and pyrazole with ozone: kinetics and mechanisms

“…Addition of ozone to the C2,C5-positions of the fivemembered ring was proposed for the reaction of furan with ozone. 59 Additionally, earlier studies which investigated the oxidation of substituted pyrroles with singlet oxygen suggested both C2,C3-and C2,C5-cycloadditions. [60][61][62] These studies found the product with two oxygen atoms added to the C2,C5-positions (equivalent to TP2) and the ring-opened product (equivalent to TP1).…”

Preparation and Use of a General Solid-Phase Intermediate to Biomimetic Scaffolds and Peptide Condensations

“…The latent aldehyde was regenerated by a brief exposure (35 min) to aqueous trifluoroacetic acid, providing resins 17a – c . Reduction to the alcohol resins 18a – c was accomplished with sodium triacetoxyborohydride in acetic acid, and this was followed by cyclitive cleavage at elevated temperatures in the presence of diisopropylethylamine (DIEA, Hünig’s base) to give the desired lactones 19a – c bearing the ozone-labile furan ring [ 33 , 34 ] in 14–25% overall yield (80–86% average yield per step over 11 steps from starting substituted Merrifield resins).…”

Oxidation and Reduction of the Pyrrole Ring

“…oxidation with molecular oxygen). Wibaut's explanation that the "abnormal" products resulted from ozonolysis of the polar structure (B32) (83,84) has been criticized by Bailey and his coworkers, (87,88) who suggested that the products are compatible with the initial addition of ozone across the 2,5-positions of the pyrrole ring. 231 and 236), involving the migration of the 2-phenyl substituent to the 3-position, have not been detected, but an unusual oxidation pathway was encountered in the reaction of 2,3,4,5-tetraphenylpyrrole with perbenzoic acid (79) in which the major product was the tetraphenylpyrazine (B24) (cf.…”