Dark singlet oxygenation of organic substrates in single-phase and multiphase microemulsion systems

Dual Catalytic Role of Molybdate Ions for Direct Conversion of Photo-oxidized Fatty Acid Methyl Esters into Keto or Hydroxy Derivatives

“…Faster reactions would occur in more halogenated solvents but dichloromethane looks to be a good compromise between hazard and availability, as recognized for the industrial photochemical production of the antimalarial artemisinine . It is noteworthy that the hydroperoxides can also be obtained using the H 2 O 2 /MoO 4 2– system, which is known as an efficient chemical source of 1 O 2 , − but in the present case, the low reactivity of the substrate would require high amounts of H 2 O 2 , and under such conditions, the photo-oxidation route is preferred …”

A New Peroxide Fragmentation: Efficient Chemical Generation of 1O2 in Organic Media

“…Singlet molecular oxygen ( 1 O 2 ), an important oxidant in chemistry, biology, and medicine, , is most commonly generated via photosensitized excitation of ground-state ( 3 O 2 ) dioxygen. , The discovery that 1 O 2 is also produced from reaction of H 2 O 2 and HOCl led to the discovery of a number of additional methods for chemical generation. ,, However, many of these “dark” oxygenations have significant limitations. Due to the short half-life of 1 O 2 in aqueous media, methods based upon reaction of H 2 O 2 with hypohalites, alkaline earth metals, transition metals, lanthanides, or metalloenzymes must typically employ biphasic or emulsion conditions for preparative oxidations . Thermal generation of 1 O 2 from phosphite ozonides, silyl hydrotrioxides, or arene endoperoxides can be conducted in organic solvents but requires preparation of unstable precursors.…”

Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals

“…This was most probably due to the relatively high hydrophobicity of the substrate, Pren-10, and consequently its low availability to singlet oxygen, which in this case was generated in a hydrophilic milieu. According to the literature, reaction with singlet oxygen generated in the H 2 O 2 /molybdate system was effective for oxidation of citronellol to produce rose oxide via the formation of hydroperoxides and diols [ 13 ] and to obtain several other products [ 14 ]. The reaction is claimed to proceed most efficiently in methanol or ethanol with Li 2 MoO 4 as the catalyst [ 29 ].…”

“…the disproportionation reaction of hydrogen peroxide with the use of molybdate ions as a catalyst [ 12 ]. This reaction has been used previously for oxidation of citronellol to produce rose oxide via the formation of hydroperoxides and diols [ 13 ], and to obtain several other products [ 14 ]. Photo-catalytic generation of singlet oxygen is achieved by photosensitization with many substances, such as porphyrins [ 15 ], titanium dioxide [ 16 ] or rose bengal (RB) [ 17 ].…”