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With acetic acid; In dichloromethane; for 6h;Molecular sieve; Inert atmosphere; Cooling with ice; |
General procedure: DMBIH 1a,7a 1b,8b, and 1g,8c are known compounds. 1c, 1d, 1e,and 1f were prepared by using modified literature procedures.6a,8b,c,10g A typical procedure for preparation of 1b is describedbelow. To a CH2Cl2 (10 mL) containing N,N0-dimethyl-o-phenylenediamine(DMPDA) (1.38 g, 10.1 mmol) with molecular sieves 4A(ca. 10g) under N2 seated in ice-water bath was slowly added 1-naphthoaldehyde (1.42 mL, 10.5 mmol) in CH2Cl2 (20 mL). Afteraddition of acetic acid (0.23 mL, 4.0 mmol), the resulting mixture was stirred for 6 h in an ice-water bath and then molecular sieveswere removed by filtration. The residue obtained after concentrationof the filtrate in vacuo was subjected to column chromatography(benzene with 1% triethylamine) to give 1b (1.85 g, 6.8 mmol,67%). In a similar fashion, 1c (1.61 g, 5.9 mmol, 71%) from DMPDA(1.12 g, 8.2 mmol) and 1e (1.30 g, 4.0 mmol, 50%) from DMPDA(1.09 g, 8.0 mmol) were prepared. 1d (1.74 g, 5.0 mmol, 61%) fromDMPDA (1.12 g, 8.2 mmol) was rinsed with MeOH after columnseparation. While 1b, 1c, and 1e were crystallized from dimethoxyethaneand EtOH, 1d was crystallized from CH2Cl2 and MeOHbefore using for the photoreactions. 1f (595 mg, 2.1 mmol, 49%)from DMPDA (584 mg, 4.3 mmol) was obtained by rinsing the solidwith EtOH after column chromatography (EtOAc/benzene1/6with 1% triethylamine), and then used for the photoreaction. |
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In dichloromethane; at 0 - 20℃; for 12h;Molecular sieve; Inert atmosphere; |
General procedure: (Step 1) A mixture of N,N'-dimethyl-N,N'-di(p-toluenesulfonyl)-o-phenylenediamine (9) (4.50 g, 10.1 mmol) and concentrated sulfuric acid (4 mL) was heated at 85 C for 4 h, and then poured into ice. To this was slowly added 4M aqueous sodium hydroxide and the resulting mixture was basified. The mixture was extracted with CH2Cl2, and the extract was washed with brine before dried over sodium sulfate. Evaporation of the extract gave crude N,N'-dimethyl-o-phenylenediamine (10) as brown oil. This crude product was used for the following reaction without purification, because it was found to be unstable under air. (Step 2) To a solution of 10 in dry CH2Cl2 (10 mL) with molecular sieves 4A was slowly added 4-anisaldehyde (1.2 mL, 9.9 mmol) in dry CH2Cl2 (5 mL) at 0 C under an argon atmosphere. The resulting mixture was stirred at room temperature for 12 h, and filtered through a pad of Celite. The filtrate was concentrated, and the residue was purified by chromatography on silica gel (hexane/ethyl acetate = 20 :1 as eluent) to obtain crude as a yellow oil. Yellow oil obtained after evaporation were recrystallized from ethanol under an argon atmosphere, and filtrated to obtain 2a (4.1 mmol, 40% yield) as colorless crystal. |
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