In pursuit of our continued interest in the development of solvent-free and green synthetic procedures, we decided to explore the use of tartaric acid catalyst for synthesis of polysubstituted quinolines via Friedlander condensation in high to excellent yields at 70 °C under solvent-free conditions. Initially the reaction between 2-aminobenzophenone (1.0 mmol) and dimedone (1.0 mmol), as the model reaction was examined in the presence varying amount of tartaric acid as catalyst and the results are presented in Table 1. The best result was achieved by carrying out the reaction with 15 mol% of catalyst (Table 1, entry 4). Use of a higher amount of catalyst did not improve the yield while a decrease in the amount of catalyst decreases the yield
…show more content…
To optimize the amount of catalyst and the temperature, reaction between β-naphthol (4), benzaldehyde (5) and dimedone (6) as a model one was performed in the presence of varying amounts of catalyst (Table 3). The product yield increased, and the time for reaction completion decreased upon an increase in the amount of tartaric acid up to 15 mol% catalyst and 70 °C. Any further increase in the amount of catalyst or the temperature did not significantly improve the results. It is important to note that in the absence of catalyst a trace of product was observed (Table 3, entry 1). The role of the temperature in the synthesis of 12-(phenyl)-9,9-dimethyl-8,9,10,12-tetrahydrobenzo[α]xanthenes-11-one was investigated in the presence of tartaric acid as the catalyst. Best results were obtained at 70 °C in the presence of 15 mol % of catalyst (Table3, entry 4). After the optimization of the reaction conditions and to show the generality of the method we used the optimized conditions for the synthesis of different types of 12-aryl-tetrahydrobenzo[α]xanthene-11-ones by using of β-naphthol (4, 1.0 mmol), aromatic aldehydes derivatives (5, 1.0 mmol) and dimedone (6, 1.0 mmol). The reaction is fairly general, clean, rapid, and efficient. The experimental procedure is very simple …show more content…
For this purpose, the condensation of benzaldehyde (1 mmol) with dimedone (2 mmol) (Scheme 3) was optimized in terms of the catalyst amount and temperature, under solvent-free conditions; the results are summarized in Table 5. The logical results were obtained when 15 mol% of tartaric acid was utilized at 70°C (Table 5, entry 4). In another study, when the reaction was carried out at 80ºC, the product was obtained in 92% yield at 10 min in comparison with 70ºC (Table 5, entry 8). Nevertheless, 70ºC was selected as optimal reaction temperature, because one aim of this work was performing the reaction in milder reaction conditions with respect to the reported works, and this was more logical. The efficiency and the generality of the catalyst were examined by the reaction of different arylaldehydes (having electron-withdrawing substituents, electrondonating substituents) with dimedone. The results are shown in Table 6. As it can be seen from the Table, all reactions were achieved efficiently, and afforded the corresponding 1,8-dioxo-octahydroxanthenes in excellent yields (85-94%), and in short reaction times (10- 20 min). Thus, tartaric acid was efficient and general. To show the merit of our catalyst with respect to the reported catalysts
To optimize the amount of catalyst and the temperature, reaction between β-naphthol (4), benzaldehyde (5) and dimedone (6) as a model one was performed in the presence of varying amounts of catalyst (Table 3). The product yield increased, and the time for reaction completion decreased upon an increase in the amount of tartaric acid up to 15 mol% catalyst and 70 °C. Any further increase in the amount of catalyst or the temperature did not significantly improve the results. It is important to note that in the absence of catalyst a trace of product was observed (Table 3, entry 1). The role of the temperature in the synthesis of 12-(phenyl)-9,9-dimethyl-8,9,10,12-tetrahydrobenzo[α]xanthenes-11-one was investigated in the presence of tartaric acid as the catalyst. Best results were obtained at 70 °C in the presence of 15 mol % of catalyst (Table3, entry 4). After the optimization of the reaction conditions and to show the generality of the method we used the optimized conditions for the synthesis of different types of 12-aryl-tetrahydrobenzo[α]xanthene-11-ones by using of β-naphthol (4, 1.0 mmol), aromatic aldehydes derivatives (5, 1.0 mmol) and dimedone (6, 1.0 mmol). The reaction is fairly general, clean, rapid, and efficient. The experimental procedure is very simple …show more content…
For this purpose, the condensation of benzaldehyde (1 mmol) with dimedone (2 mmol) (Scheme 3) was optimized in terms of the catalyst amount and temperature, under solvent-free conditions; the results are summarized in Table 5. The logical results were obtained when 15 mol% of tartaric acid was utilized at 70°C (Table 5, entry 4). In another study, when the reaction was carried out at 80ºC, the product was obtained in 92% yield at 10 min in comparison with 70ºC (Table 5, entry 8). Nevertheless, 70ºC was selected as optimal reaction temperature, because one aim of this work was performing the reaction in milder reaction conditions with respect to the reported works, and this was more logical. The efficiency and the generality of the catalyst were examined by the reaction of different arylaldehydes (having electron-withdrawing substituents, electrondonating substituents) with dimedone. The results are shown in Table 6. As it can be seen from the Table, all reactions were achieved efficiently, and afforded the corresponding 1,8-dioxo-octahydroxanthenes in excellent yields (85-94%), and in short reaction times (10- 20 min). Thus, tartaric acid was efficient and general. To show the merit of our catalyst with respect to the reported catalysts