| 94% |
With pyridinium chlorochromate; In dichloromethane; at 55℃; |
General procedure: Variant C: (0530) Adapting a literature known protocol (Corey and Suggs, Tetrahedron Lett., 1975, 16(31), 2647-2650; and Fujikawa, et al., J. Am. Chem. Soc., 2008, 130, 14533-14543), to a solution of the benzylic alcohol (20 mmol) in dichloromethane (DCM) (100 mL) is added commercial pyridinium chlorochromate (Pyr+CrO3Cl-, PCC) (28-40 mmol). The reaction mixture is heated to reflux (55 C. oil bath temperature) for 1-4 hours. The reaction is monitored by TLC and/or LCMS to completion. The reaction is cooled to room temperature. Work-up and product isolation and purification are conducted as described for Variant B. |
| 94% |
With pyridinium chlorochromate; In dichloromethane;Reflux; |
General procedure: Variant C: Adapting a literature known protocol (Corey and Suggs, Tetrahedron Lett, 1975, 16(31), 2647-2650; and Fujikawa, et al., J. Am. Chem. Soc, 2008, 130, 14533- 14543), to a solution of the benzylic alcohol (20 mmol) in dichloromethane (DCM) (100 mL) is added commercial pyridinium chlorochr ornate (Pyr+Cr03Cl~, PCC) (28-40 mmol). The reaction mixture is heated to reflux (55C oil bath temperature) for 1-4 hours. The reaction is monitored by TLC and/or LCMS to completion. The reaction is cooled to room temperature. Work-up and product isolation and purification are conducted as described for Variant B. Following the General Procedure of Description 2 (Variant A), 2-methyl-5-nitro- benzaldehyde (lb) (Beech, J. Chem. Soc. I, 1967, 2374-2375) was prepared from 2-methyl-5- nitro-phenyl)methanol (la) (16.3 g, 97.3 mmol) in the presence of dimethylsulfoxide (DMSO) (56.8 mL, 62.6 g, 0.80 mol), triethylamine (TEA, Et3N) (69.5 mL, 50.6 g, 0.50 mmol), and sulfur tri oxide pyridine complex (S03 pyridine) (47.8 g, 0.30 mol) in dichloromethane (600 mL). Purification by silica gel column chromatography using a mixture of ethyl acetate (EtOAc) and hexane (EtOAc/hexane = 1 :4, v/v) afforded 12.6 g (78% yield) of the target compound (lb) as a yellow-beige solid. [0593] Following the General Procedure of Description 2 (Variant B), 2-methyl-5-nitro- benzaldehyde (lb) (Beech, J. Chem. Soc. I, 1967, 2374-2375) was prepared from 2-methyl-5- nitro-phenyl)methanol (la) (4.03 g, 24.1 mmol) in the presence of manganese dioxide (Mn02) (22 g, 254 mmol) in dichloromethane (DCM) (100 mL). Work-up afforded 3.56 g (89% yield) of the target compound (lb) as a pale yellow to beige solid. The material was of sufficient purity to be used directly in the next step without further isolation and purification. [0594] Following the General Procedure of Description 2 (Variant C), 2-methyl-5-nitro- benzaldehyde (lb) (Beech, J. Chem. Soc. I, 1967, 2374-2375) was prepared from 2-methyl-5- nitro-phenyl)methanol (la) (5.00 g, 29.9 mmol) in the presence of pyridinium chlorochromate (PCC) (9.02 g, 41.9 mmol) in dichloromethane (DCM) (150 mL). Purification by silica gel column chromatography using mixtures of ethyl acetate (EtOAc) and hexane (EtOAc/hexane = 1 :4, v/v? EtOAc/hexane = 1 :2, v/v) afforded 4.67 g (94% yield) of the target compound (lb) as a yellow-beige solid. Rf. -0.76 (EtOAc/Hxn = 1 :2, v/v). 1H MR (300 MHz, CDC13): delta 10.32 (s, 1H), 8.65 (dd, J= 2.7 Hz, 1H), 8.31 (dd, J= 8.4, 2.4 Hz, 1H), 7.47 (d, J= 8.4 Hz, 1H), 2.79 (s, 3H) ppm. The compound is also commercially available. |
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