Photochemistry of chromones: photoreorganisation of 3-alkoxy-2-thienyl-4-oxo-4H-1-benzopyrans

Photochemical transformations of 1,10-decylbischromones: effect of spacer length

“…The photoproducts 3 and 4 are formed through the involvement of only one of the two chromophores as revealed by two IR absorptions (1635, 1653 and 1631, 1649 The stereochemical features of hydrogens at C-3a, C-4 and C-11b in photoproducts 5 and 7 were ascertained from J and Ф parameters: that all the hydrogens are present on the same side is evident from J 3a,4 = 11 Hz (Ф = 0 o ) and J 11b,3a = 8.5 Hz (Ф ~27 o ). 13,15,16 The heavier alkyl group at C-4 is present in the preferred Ψ-equatorial conformation and ring C in the half chair form.…”

“…The bischromones 1 and 2 needed for this study were synthesized by reacting 6-chloro-3-hydroxy-2-(2'-thienyl)-4-oxo-4H-1-benzopyran 13 and 6-chloro-3-hydroxy-2-phenyl-4-oxo-4H-1-benzopyran, 14 respectively, with 1,10-dibromodecane in the presence of dry K 2 CO 3 /Acetone and Similarly, further photolysis of 2 in benzene solution furnished three photoproducts 7-9. The structures of these photoproducts were confirmed by comparison of their IR / 1 H NMR spectra with those of 1 and 2 (see experimental) and the similar photoproducts obtained from the photoirradiation of bischromones 10 11 and 12.…”

Photochemistry of 3-alkoxychromones: photocyclisation of 2-aryl-6-chloro-3-{(thiophen-2-yl)methoxy}chromones

“…The 2-aryl-3-{(thiophen-2-yl)methoxy}chromones 2(a-g) were obtained by reacting 3-hydroxybenzopyrans [16][17] 1(a-g) with 2-(chloromethyl)thiophene 18 using anhydrous K 2 CO 3 /n-Bu 4 N + I -in anhydrous acetone as the solvent as shown in Scheme 1.…”

Photochemical Transformations of Some 2-(5-Methylthiophen-2-yl)-3-[(naphthalen-2-yl)methoxy]-4H-chromen-4-ones Involving Type-II Process

“…An overall programme on photo-transformations of variously substituted chromones has been initiated in our laboratory. The substituted chromones [9][10][11][12][13][14][15] bearing acyclic and monocyclic moieties in the 3-alkoxy group have been studied.…”

“…Our objectives are (i) to study the effect of naphthyl group on 1,4-biradical formed in situ to form photoproducts (ii) to determine the influence of different substituents on the chromenone moiety and (iii) to learn more about the potential utility of the photo-induced intramolecular hydrogen transfer [9][10][11][12][13][14][15][16] for the synthesis of polycyclics.…”