The photochemistry of flavanone

Abstract

On U.V. irradiation, flavanone rearranges to undergoes fragmentation to yield a highly reactive 4-phenyldihydrocoumarin and 2'-hydroxychalcone, and keto-keten.

Photochemistry of Flavonoids

“…Mack and Pinhey [ 60 ] transformed flavanone 68 , via fragmentation of the heterocyclic benzylic O-C bond, into 2'-hydroxychalcone 70 (20%) in benzene at 250 nm. They also isolated salicylic acid ( 73 , 4%) via the subsequent fragmentation of the C2-C3 bond to form a ketene 72 that can be trapped with water or methanol.…”

Photochemical transformations of small ring heterocyclic compounds. 91. Photochemistry of the chroman and 3-chromanone ring systems. An example of tautomeric control of excited-state chemistry

“…In addition, a number of reports dealing with the aromatization of arene oxides (22) to 4-indanols (24) have shown that these reactions proceed via a spiroketone (23) intermediate. [39][40][41][42] These reports suggested that a related rearrangement might also occur upon irradiation of the chroman ring (25). In order to test for this possibility, we investigated the photochemical behavior of several substituted chromans.…”

“…The resulting yellow solution was stirred for 15 min at 0 °C and then 200 mg of methyl iodide was added. The solution was allowed to warm to room temperature and then stirred at 25 °C for 2 h. The reaction mixture was diluted with ether and washed with water. The ethereal layer was dried over magnesium sulfate and concentrated under reduced pressure to give 206 mg (92%) of 3-methyl-3-phenyl-2-benzofuranone: IR (neat) 5.53, 6.18, 6.24, 6.85, 8.12, 9.67,11.20,13.26, and 14.37 µ ; NMR ICDCI3, 60 MHz) r 8.18 (s, 3 H) and 2.9-2.6 (m, 9 H).…”

Specific photoreactions of flavanones typical of n,π* and π,π* characters in lowest triplet states

“…On irradiation in benzene some other minor products were detected (t.l.c. ), perhaps (8) and (9) * or derivatives.…”