Flavanones oxidation

Sutter A, Poulton J, Grisebach H (1975) Oxidation of flavanone to flavone with cell-free extracts from young parsley leaves. Arch Biochem Biophys 170(2) 547-556... 

Stotz G, Forkmann G (1981) Oxidation of flavanones to flavones with flower extracts of Antirrhinum majus (snapdragon). Z Naturforsch 36C 737-741... 

Hashim, M.F. et al.. Reaction mechanism of oxidative rearrangement of flavanone in isofiavone biosynthesis. FEBS Lett., 271, 219, 1990. 

Tetrahydroquinolones can be transformed also by (diacetoxyiodo)benzene 3 to the aromatic arylquinolines, a structure found in various alkaloids [101]. Depending on the reagent, it is possible to oxidize flavanones 50 either into flavones 51 or into rearranged isoflavones 52 [102, 103]. (Diacetoxyiodo)-benzene 3 or the polymer-supported reagent 18 were also efficient reagents for the oxidation of 1,4-dihydropyridines 53 to the corresponding pyridine derivatives 54, Scheme 23 [104]. 

Flavanones - Isoflavones. Although Koser s reagent (1) is known to effect a-tosyloxylation of ketones,1 the reaction with flavanones (2) results in an oxidative 1,2-aryl shift to provide isoflavones (3) in 74-80% yield.2 This conversion has been effected previously with thallium salts. 

Baeyer-Villiger rearrangement of flavanone derivatives with MTO/H2O2 was first reported in 2001 by Saladino and coworkers and has successfully been applied for various substituted flavanones (Scheme 14). In the case where R1, R2, and R3 are methoxy groups (naringenin) or when all R-groups are methoxy groups (hesperetin), oxidation toward the benzoquinone product is the major product... 

Scheme IS Oxidation and subsequent acetylation of substituted flavanones with MTO/IJHP [104]...

Another type of flavones bears a double bond in the 0-heterocyclic ring and can also be oxidatively functionalized at this bond with MTO (Scheme 15). Using the MTO/UHP system with substituted flavanone in refluxing methanol, followed by acetylation, cis- and ri[Pg.163]

Oxidation of flavanones with manganese(m) acetate affords the corresponding flavones in high yield (Equation 313) <2005SC2723>. 

Simple alcohols are not oxidized readily by BTI however, flavonols in the presence of pyridine in boiling acetonitrile gave flavanones in excellent yields [60] ... 

Chlorination of aldoximes. NCS converts aryl aldoximes to hydroxamic acid chlorides without significant chlorination of the aryl group. This reaction has been used for a novel synthesis of nitrile oxides. Thus reaction of salicylaldoxime (1) with NCS followed by dehydrochlorination with pyridine generates a nitrile oxide, which is trapped by styrene to give the isoxazoline 2. The N-O bond can be cleaved by catalytic hydrogenation to 3, which is converted into the chalcone 4 on elimination of water. This product can be converted by classical methods to the flavanone 5 and the flavone 6. An analogous route can be used to synthesize 2-... 

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