A highly efficient green synthesis of 1, 8-dioxo-octahydroxanthenes.

SmCl3 (20 mol%) has been used as an efficient catalyst for reaction between aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione at 120°C to give 1,8-dioxo-octahydroxanthene derivatives in high yield. The same reaction in water, at room temperature gave only the open chain analogue of 1,8-dioxo-octahydroxanthene. Use of eco-friendly green Lewis acid, readily available catalyst and easy isolation of the product makes this a convenient method for the synthesis of either of the products.

6,6'-dimethoxy-2,2'-[(1R,2R)-cyclohexane-1,2-diylbis(nitrilomethylidyne)]diphenol: three C-H...O hydrogen bonds generate a three-dimensional framework.

Molecules of the title compound, alternatively called (R,R)-N,N'-bis(3-methoxysalicylidene)-trans-cyclohexane-1,2-diamine, C(22)H(26)N(2)O(4), contain two intramolecular O-H.N hydrogen bonds and adopt a conformation with approximate twofold rotational symmetry. The molecules are linked by three C-H.O hydrogen bonds [H.O = 2.45-2.55 A, C.O = 3.329 (2)-3.398 (2) A and C-H.O = 142-172 degrees ] into a continuous framework.