Syntheses and Crystal Structures of 1,5-Dioxaspiro[5.5]undecane-2,4-dione Derivatives

The 3-(2,3,4-trimethoxybenzylidene)-1,5-dioxaspiro[5.5]undecane-2,4-dione 1 and 3-(3,4,5-trimethoxybenzylidene)-1,5-dioxaspiro[5.5]undecane-2,4-dione 2 have been synthesized and characterized by X-ray single-crystal diffraction, IR and UV–Vis. Compound 1 belongs to the orthorhombic system, space group Pna21 with a = 10.182(2) A, b = 11.828(2) A, c = 14.356(3) A, α = 90°, β = 90°, γ = 90°, V = 1,729.0(6) A3, Z = 4. Compound 2 is of Triclinic system, space group P-1 with a = 8.7807(18) A, b = 9.4383(19) A, c = 11.450(2) A, α = 98.64(3)°, β = 103.28(3)°, γ = 99.44(3)°, V = 893.4(3) A3, Z = 2. It is very interesting that there are only C–H···O and C–H···π intermolecular interaction in the 1, while there are still π···π stacking interactions except for C–H···O and C–H···π intermolecular interaction in the structure of 2. Two new spiro compounds, 3-(2,3,4-trimethoxybenzylidene)-1,5-dioxaspiro[5.5]undecane-2,4-dione 1 and 3-(3,4,5-trimethoxybenzylidene)-1,5-dioxaspiro[5.5]undecane-2,4-dione 2 have been synthesized and characterized by X-ray single-crystal diffraction, IR and UV–Vis.