(E)-3-(2H-1,3-Benzodioxol-5-yl)-1-(7-hydroxy-5-methoxy-2,2-dimethylchroman-8-yl)prop-2-en-1-one

The reaction of 5,6-(2,2-dimethylchromane)-2-hydroxy-4-methoxyacetophenone and 3,4-methlenedioxybenzaldehyde affords the title chalcone derivative, C22H22O6. The two benzene rings are connected through a —C(=O)—CH=CH— (propenone) unit, which is in an E conformation; the ring with the hydroxy substitutent is aligned at 6.2 (1)° with respect to this unit, whereas the ring with the methylenedioxy substituent is aligned at 8.2 (1)°. The dihdral angle between the rings is 14.32 (7)°. The hydroxy group engages in an intramolecular hydrogen bond with the carbonyl O atom of the propenone unit, generating an S(5) ring.

The reaction of 5,6-(2,2-dimethylchromane)-2-hydroxy-4methoxyacetophenone and 3,4-methlenedioxybenzaldehyde affords the title chalcone derivative, C 22 H 22 O 6 . The two benzene rings are connected through a -C( O)-CH CH-(propenone) unit, which is in an E conformation; the ring with the hydroxy substitutent is aligned at 6.2 (1) with respect to this unit, whereas the ring with the methylenedioxy substituent is aligned at 8.2 (1) . The dihdral angle between the rings is 14.32 (7) . The hydroxy group engages in an intramolecular hydrogen bond with the carbonyl O atom of the propenone unit, generating an S(5) ring.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
We intend to use the intensely yellow-orange title compound, (I), in the synthesis of other compounds. A related structure was reported in the previous paper. Its two benzene rings are connected through the -C(═ O)-CH═CH-unit, which is of an E configuration; the ring with the hydroxy substitutent is aligned at 6.2 (1) ° with this unit whereas the ring with the methyleledioxy substituent is aligned at 8.2 (1) °. The hydroxy group engages in intramolecular hydrogen bonding with the carbonyl O atom of the unit (Fig. 1).

Experimental
A solution of 2-hydroxy-4-methoxy-5,6-(2,2-dimethylchromane)acetophenone (150 mg, 0.68 mmol) and methylenedioxybenzaldehyde (150 mg, 0.45 mmol) in ethanol (10 ml) was treated with 50% potassium hydroxide (1 ml). The mixture was stirred for 48 h. The mixture was poured into iced water (30 ml); this was acidified with 10% hydrochloric acid. The mixture was extracted with dichloromethane (3 x 20 ml). The organic layer was washed with water (3 x 10 ml) and brine (3 x 5 ml) followed by drying over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to yield a dark orange syrup. The syrup was subjected to VLC for purification by using silica gel and eluting with a hexane:ethyl acetate solvent system (9:1) to give (I) (520 mg, 30%) as yelloiwsh orange blocks, m.p. 395-399 K. The formulation was established by 1 H-and 13 C-NMR spectroscopy.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.95 to 0.98 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2 to 1.5U eq (C).
The hydroxy H-atom was located in a difference Fourier map, and was refined with a distance restraint of O-H 0.84±0.01 Å; its temperature factor was freely refined.