Photodimerization of chromone

Abstract

Irradiation of the simple chromone (benzo-gamma-pyrone) resulted in the formation of two types of dimers, anti-HT (head-to-tail) and trans-fused HT isomers, whose structures were established by X-ray structural analysis.

Modulating the reactivity of chromone and its derivatives through encapsulation in a self-assembled phenylethynylene bis-urea host

“…After UV-irradiation of host 1Áchromone for 3 h, we observed 19% conversion of chromone to afford two photodimers ( Table 2, entry 2). The 1 H NMR resonances for the major product, matched those reported for the anti-HT photodimer [15]. GC/MS was used to further monitor the selectivity and showed an anti-HT selectivity of 87.4% with the minor photodimer formed in 12.6% selectivity (see SI for GC/MS trace).…”

“…Thus, we sought to grow single crystals of these compounds suitable for X-ray diffraction studies. Crystals of chromone were obtained from a mixture of chloroform/hexanes [15,36] while crystals of 6-fluorochromone [36], 7-hydroxy-4-chromone and 3-cyanochromone were obtained by the cooling of hot acetonitrile solutions (25 mg/mL). Two new structures are reported here.…”

“…In solution, simple chromones may undergo photodimerizations and photoaddition reactions [14] with olefins and acetylenes. For example, benzene solution UV-irradiation of chromone produced anti-HT and trans-fused HT dimers in $1:1 ratio with 30% conversion and 99% yield [15]. The dimerization efficiency greatly depended upon the concentration of chromone [16].…”

Photochemical studies: Chromones, bischromones and anthraquinone derivatives

“…The photoirradiation of the chromone 11 led to the formation of two types of dimers, anti-HT 12 (head-to-tail) and trans-fused HT 13 isomers (Sakamoto et al, 2009), whose structures were established with the help of X-ray structural analysis (Scheme 2).…”

“…Khelin 1 was the first chromone extracted from Ammi visnaga, used as a diuretic to relieve renal colic (Edwards and Howell, 2000), as a smooth muscle relaxant (Nordlund, 2006) and in the treatment of vitiligo, a pigmentation disorder (De Leeuw et al, 2011). Other chromone derivatives for example sodium cromoglycate 2, diosmin 3 and flavoxate 4 are used as a mast cell stabilizer in allergic asthma and allergic conjunctivitis, for the treatment of various diseases and as a smooth muscle relaxant to treat urge incontinence (Holgate and Polosao, 2008;Frick, 2000;Ruffmann, 1988). These pharmacological properties have been the major incentive behind the synthesis of chromones which are obtained via different routes.…”