The title compound, C19H17NO5, comprising two stereogenic C atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a half-chair conformation, while the isoxazole ring adopts an envelope conformation with the C atom bonded to the meth-oxy-phenyl group as the flap. The dihedral angle between the mean plane of the pyran ring and the adja...

In the title compound, C(27)H(27)NO(4), the five-membered isoxazole ring adopts an envelope conformation and the six-membered pyran ring adopts a half-chair conformation. The dihedral angle between the mean planes of the isoxazole ring and the chromene ring system is 54.95 (4)°.

In the title compound, C(25)H(25)NO(4), the pyrrolidine ring exhibits an envelope conformation and the tetra-hydro-pyran ring exhibits a half-chair conformation. The crystal structure is stabilized by inter-molecular C-H⋯π inter-actions.

In the title compound, C(27)H(27)NO(3), the pyrrolidine ring exhibits a twist conformation and the piperidine ring exhibits a chair conformation. The pyrrolidine ring makes dihedral angles of 54.47 (5), 51.50 (5) and 73.37 (6)° with the napthalene ring system and the tetra-hydro-pyran and phenyl rings, respectively. The structure is stabilized by intra-molecular C-H⋯O and C-H⋯N inter-actions.

The equilibrium between different tautomers that can be colored or colorless is an important feature for rhodamine dyes. Presently, this phenomenon mostly discussed B. Herein, we studied the tautomerism and acid–base dissociation (HR+ ⇄ R + H+) of a set rhodamines in organic media. Form mixture zwitterion R± lactone R0. Absorption spectra 90 mass% aqueous acetone reflects correlation dyes struc...