RESUMO
This work discloses a two-step, one-pot approach to ω-functionalized esters via cleavage of the alicyclic fragment of cycloalkanone semicarbazones. This approach is based on a combination of the synthesis of various alkoxyhydroperoxides via cycloalkanone semicarbazone ozonolysis and in situ interaction of these peroxides with transition metal salts, leading to cleavage of the aliphatic cycle and subsequent ω-functionalized ester formation. A broad series of ω-halogen or pseudohalogen esters have been successfully synthesized in yields ranging from 23 to 73% per starting semicarbazone. A major advantage of the approach is the ability to use different cycloalkanone semicarbazones, including those with large cycles and substituents in them. The possibility of carrying out ozonolysis in the presence of various alcohols makes it possible to obtain the corresponding esters of ω-substituted carboxylic acids.
RESUMO
Four heteroatoms dance in the cascade of four pericyclic reactions initiated by ozonolysis of CâN bonds. Switching from imines to semicarbazones introduces the fifth heteroatom that slows this dance, delays reaching the thermodynamically favorable escape path, and allows efficient interception of carbonyl oxides (Criegee intermediates, CIs) by an external nucleophile. The new three-component reaction of alcohols, ozone, and oximes/semicarbazones greatly facilitates synthetic access to monoperoxyacetals (alkoxyhydroperoxides).
RESUMO
Alkene ozonolysis is mostly known as a textbook reaction, resulting in carbonyl compounds. The combination of ozone and hydroperoxide was found to lead to the construction of more oxygen-rich compounds, unsymmetrical geminal bisperoxides, avoiding as well further oxidation with ozone, hydroperoxide, and oxygen as peroxide rearrangements. The discovered three-component synthesis provided alkylperoxy hydroperoxides in 41-63% yield from alkenes.