| Popis: |
Various 3-substituted isoquinolin-4-ols have been successfully synthesised by two different methodologies. Treatment of isoquinoline N-oxide with p-toluenesulfonyl chloride, provided 4-(p-toluenesulfonyloxy) isoquinoline in 30% yield and high purity via rearrangement of an intermediate N-(p-toluenesulfonyloxy) compound. Isoquinolin-4-ol was then obtained, after acid hydrolysis of 4-(p-toluenesulfonyloxy) isoquinoline. 3-Methylisoquinolin-4-ol has been synthesised in a similar manner and yield, from 3-methylisoquinoline N-oxide via 3-methyl-4-(p-toluenesulfonyloxy) isoquinoline. 4-(p-Nitrobenzenesulfonyloxy) isoquinoline has been obtained from the reaction between isoquinoline N-oxide and p-nitrobenzenesulfonyl chloride. The regioselectivity of these rearrangements was in contrast to that of isoquinoline N-oxide with p-(2,4-dinitrobenzenesulfonyl chloride, which gave 1-(2,4-dinitrobenzenesulfonyloxy) isoquinoline. The Mannich reaction was used to functionalise isoquinolin-4-ol at the 3-posiotn, giving 3-(dimethylaminomethyl)-isoquinolin-4-ol and sodium 3-aza-3-methyl-4(4-hydroxyisoquinolin-3-yl)butane-1-sulfonate. These derivatives however, proved unstable to attempted azo coupling at the unsubstituted t-position. FVP of various methyl Meldrum’s acid derivatives has provided a novel reduction of the azo group to the corresponding hydrocarbon, but the reaction was shown to take place in the FVP inlet, and therefore is of limited synthetic use. 3-Phenylisoquinolin-4-ol has been synthesised via an isoindolone precursor in 20% yield, under FVP conditions, but the method has proved inapplicable to alkyl derivatives. A novel azo cyan dye was synthesised from the reaction between 3-phenylisoquinolin-4-ol and a diazonium salt derived from 2-amino-6-chloro-4-sulfonamidophenol. The metallised complex of the azo dye was then obtained after reaction with nickel (II) acetate tetrahydrate. |
