Syntheses and Crystal Structures of Two Apigenin Alkylation Derivatives

Two apigenin alkylation derivatives, 4′,7-dimethoxyl-5-hydroxyflavone (I) and 4′,7-diethoxyl-5-hydroxyflavone (II), have been synthesized and their crystal structures were determined by 1 H NMR and single crystal X-ray diffraction study. (I) is triclinic, space group P −1 with a = 7.120(5) Å, b = 7.297(5) Å, c = 13.559(10) Å, α = 89.313(12)°, β = 86.298(12)°, γ = 83.999(13)° and Z = 2. (II) is monoclinic, space group P 2 1 /c with a = 16. 309(4) Å, b = 7.303(2) Å, c = 15.185(4) Å, α = 90.00°, β = 115.70(2)°, γ = 90.00° and Z = 4. They have the same flavone skeleton which is composed of a benzopyranone moiety and a phenyl moiety. Molecules of (I) are linked into a two-dimensional network by a combination of C–H···O hydrogen bond and π–π stacking interactions. (II) shows some discrepancies with (I) and the molecules are linked into a column by π–π stacking interaction. Graphical Abstract Two apigenin alkylation derivatives, 4′,7-dimethoxyl-5-hydroxyflavone (I) and 4′,7-diethoxyl-5-hydroxyflavone (II) were synthesized and their crystal structures were determined by single-crystal X-ray diffraction. Hydrogen bonding and π–π stacking interactions assemble (I) into a two-dimensional network, and in the crystal structure of (II), π–π stacking interaction leads to the formation of a column.