(E)-2,2-Dimethyl-5-(3-phenyl­allyl­idene)-1,3-dioxane-4,6-dione

The title compound, C15H14O4, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and (Z)-3-phenyl­acryl­aldehyde in ethanol. The dioxane ring is in a sofa conformation with the C atom bonded to the two methyl groups forming the flap. With the exception of the flap atom and the methyl group C atoms, all other non-H atoms are essentially planar, with an r.m.s. deviation of 0.067 (1) Å. The crystal structure is stabilized by weak inter­molecular C—H⋯O hydrogen bonds

2,2-Dimethyl-5-(2,3,4-trimeth­oxy­benzyl­idene)-1,3-dioxane-4,6-dione

The title compound, C16H18O7, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and 2,3,4-trimeth­oxy­benzaldehyde. The 1,3-dioxane ring is in a slightly distorted boat conformation. The crystal structure is stabilized by weak inter­molecular C—H⋯O hydrogen bonds

5-(3,4-Dimethyl­benzyl­idene)-2,2-dimethyl-1,3-dioxane-4,6-dione

The title compound, C15H16O4, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and 3,4-dimethyl­benzaldehyde in ethanol. The 1,3-dioxane ring exhibits an envelope conformation. In the crystal, mol­ecules are linked by weak inter­molecular C—H⋯O hydrogen bonds, forming chains parallel to the b axis

5,5′-[(2,4-Dichloro­phen­yl)methyl­ene]bis­(2,2-dimethyl-1,3-dioxane-4,6-dione)

The title compound, C19H18Cl2O8, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and 2,4-dichloro­benzaldehyde in ethanol. The two 1,3-dioxane rings exhibit boat conformations. In the crystal, mol­ecules are linked by weak inter­molecular C—H⋯O and C—H⋯Cl hydrogen bonds, forming chains parallel to the a axis

2,2-Dimethyl-5-[(5-methyl­furan-2-yl)methyl­idene]-1,3-dioxane-4,6-dione

The asymmetric unit of the title compound, C12H12O5, contains two independent mol­ecules. In each, the 1,3-dioxane ring adopts an envelope conformation with the dimethyl-substituted C atom forming the flap. The crystal structure is stabilized by weak inter­molecular C—H⋯O hydrogen bonds

3-(4-Bromo­benzyl­idene)-1,5-dioxaspiro­[5.5]undecane-2,4-dione

The title mol­ecule, C16H15BrO4, was prepared by the reaction of (R)-2,4-dioxo-1,5-dioxaspiro­[5.5]undecane and 4-bromo­benzaldehyde with ethanol. The 1,3-dioxane ring exhibits a distorted boat and the fused cyclo­hexane ring exhibits a chair conformation

3-(4-Fluoro­benzyl­idene)-1,5-dioxa­spiro­[5.5]undecane-2,4-dione

In the title mol­ecule, C16H15FO4, the fused 1,3-dioxane and cyclo­hexane rings exhibit a bath and a chair conformation, respectively. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers

5-(4-Hy­droxy­benzyl­idene)-2,2-dimethyl-1,3-dioxane-4,6-dione

The title compound, C13H12O5, was prepared by the reaction of 2,2-dimethyl-1,3-dioxane-4,6-dione and 4-hy­droxy­benz­alde­hyde in ethanol. The 1,3-dioxane ring is in a distorted boat conformation. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds generate R 2 2(20) rings

2-(1H-1,2,3-Benzotriazol-1-yl)-1-m-toluoylethyl 2,4-dichloro­benzoate

In the title compound, C23H17Cl2N3O3, the dihedral angles between the mean planes of the benzotriazole system and the methyl- and dichloro-substituted benzene rings are 47.72 (1) and 13.06 (1)°, respectively. In the crystal structure, inter­molecular C—H⋯O and C—H⋯π inter­actions help to consolidate the packing

2-(1H-Benzotriazol-1-yl)-1-(4-ethyl­benzo­yl)ethyl 2-chloro­benzoate

In the crystal structure of the title compound, C24H20ClN3O3, weak inter­molecular C—H⋯O hydrogen bonds link the mol­ecules into chains extended along the a axis. The crystal studied was found to be an inversion twin