2
43
Molecules 2000, 5
were recorded with a Bruker AC 200 spectrometer (200 MHz) in CDCl . The UV spectra were re-
3
corded in MeOH using a Shimadzu Graphicord UV-Visible 240 spectrophotometer. The mass spectra
(70 eV) were obtained with a Shimadzu GCMS-QP1000A mass spectrometer. All the compounds were
purified by column or thin layer chromatography on silica gel.
Typical procedure of oxidation of benzhydrols
2
,4,6,2',6'-Pentamethoxybenzophenone (2)
A mixture of 1 (100 mg), DDQ (20 mg) and PbO (140 mg) in dry benzene (20 ml) was stirred for
2
2
4 h at room temperature. The reaction was monitored by TLC (CHCl ). On completion of the reac-
3
tion, the catalyst was filtered off and the solvent removed under reduced pressure. The crude product
was purified by preparative TLC (silica gel, pet. ether/EtOAc 9:1) to furnish 2 as a colourless solid,
-
1
yield 89 mg (89%); m.p. 150°C (benzene); IR (KBr): n 1680, 1600 cm ; UV: l
332 nm; MS (m/z):
max
1
+
3
32 (M ); H NMR: 3.6 (s, 6H, 2 x OCH ), 3.62 (s, 6H, 2 x OCH ), 3.75 (s, 3H, OCH ), 6.0 (s, 2H,
3
3
3
ArH), 6.5 (d, J = 9 Hz, 2H, ArH), 7.15 (t, J = 9 Hz, 1H, ArH); (Found: C, 65.3 ; H, 6.5; C H O ; re-
18
20
6
quires C, 65.05; H, 6.07 %).
,6,2',5'-Tetramethoxybenzophenone (4)
Following the above procedure 3 (300 mg) was oxidized with DDQ (50 mg) and PbO (230 mg) to
2
2
give 4 as colourless solid , yield 224 mg (75%); m.p. 98°C (lit. [7] 97-98°C), IR (KBr): n 1675, 1600
-
1
1
+
cm ; UV: l max 302 nm; MS (m/z): 302 (M ); H NMR: 3.6 (s, 3H, OCH ), 3.75 (s, 6H, 2 x OCH ), 3.8
3
3
(
s, 3H, OCH ), 6.4 - 7.4 (m, 6H, ArH)
3
2-Methoxybenzophenone (6)
Following the above procedure 5 (200 mg) was oxidized with DDQ (50 mg) and PbO (230 mg) to
2
give 6 as colourless liquid, yield 73 mg (37%); thick liquid (lit.[8] 35-36°C), IR (film): n 1666, 1598
-
1
1
+
cm ; UV: l max 250 nm; MS (m/z): 212 (M ); H NMR: 3.71 (s, 3H, OCH ), 6.9-7.6 (m, 8H, ArH),
3
7.85 (m, 1H, ArH) .
Benzophenone (8)
Following the above procedure 7 (180 mg) was oxidized with DDQ (200 mg) and PbO (230 mg). 8
2
-
1
was obtained as colourless solid (48 h), yield 50%; m.p. 48°C; IR (KBr): n 1680, 1600 cm ; UV: l
max
-1
2
52 nm; H NMR: 7.45 (m, 4H, ArH), 7.7 (m, 6H, ArH)
Acknowledgements: We express our sincere thanks to Dr. S. K. Nayak and Dr. A. D. Deshpande for
providing the benzhydrols.