Table 2. Cu(II)-Fur-APTES/GO Catalyzed Synthesis of 1,8-Dioxo-octahydroxanthenes^a.

productc	R	R′	time (min)	yieldb (%)
3a	H	CH3	30	95
3b	3-CH3	CH3	35	93
3c	3-Br	CH3	25	90
3d	3-Cl	CH3	25	91
3e	3-OCH3	CH3	35	90
3f	4-CH3	CH3	40	89
3g	4-OCH3	CH3	50	89
3h	4-NO2	CH3	25	94
3i	4-OH	CH3	50	86
3j	4-Cl	CH3	30	92
3k	4-CN	CH3	30	95
3l	4-Br	CH3	25	92
3m	H	H	30	94
3n	3-CH3	H	35	92
3o	3-Br	H	25	94
3p	3-Cl	H	25	91
3q	3-OCH3	H	35	89
3r	2-CH3	H	50	85
3s	4-CH3	H	40	90
3t	4-NO2	H	30	95

^aReaction conditions: aromatic aldehydes (1 mmol), dimedone or 1,3-cyclohexanedione (2 mmol), catalyst (20 mg), solvent (5 mL), temperature 50 °C.

^bIsolated yields.

^cProducts were characterized by ¹H and ¹³C NMR spectroscopy.