Ozonolyses of Acetylenes: Trapping of α-Oxo Carbonyl Oxides by Carbonyl Compounds and Stabilization of α-Oxo Ozonides by Derivatizations

Ozonolyses of 2-butyne (7) or of 3-hexyne (14) in the presence of carbonyl compounds (aldehydes, ketones, acid derivatives) afforded the corresponding mostly labile monocyclic a-oxo ozonides (9, 13a, 16), which could be stabilized and, hence, isolated by subsequent conversion into a-methoximino derivatives. Ozonolyses of 1,4-diacyloxy-substituted (19) and 1-acyloxy-substituted 2-butynes (27) gave bicyclic ozonides (22,31) by intramolecular [3 + 2]-cycloadditions of the corresponding carbonyl oxide intermediates (20, 29). These ozonides could also be stabilized by reactions with O-methylhydroxylamine to give O-methyloximes (23c, 32) or with diazomethane to give epoxy ozonides (25, 34).