Rosemund von Braun reaction

There has been a plethora of recent hterature regarding the synthetic manipulations of the 2(lH)-pyrazinone skeleton. Even though the addition-elimination reactions at the C-3 position to decorate the pyrazinone scaffold are well documented [24], the versatihty of such approaches can be found somewhat limited. Selective attack of nucleophiles on the chloroimine group of the pyrazinone system can generate 3-alkoxy- and 3-amino-pyrazinones (Scheme 9) [27,28]. The 3-CN group was introduced via a Rosemund-von Braun reaction with copper(I)cyanide under harsh conditions (heating in NMP at 150 °C) [27] (Scheme 9). 

Thus another approach has to be undertaken. A better approach involves treatment of A with CuCN via the Rosemund-von Braun reaction. 

Nitriles are versatile and important components of a range of dyes, natural products, and pharmaceuticals. Aryl nitriles can be synthesized from aryl halides by direct reaction between aryl halides and copper cyanide, known as the Rosemund von Braun reaction [36]. These cyanation reactions can have several disadvantages, in particular the long reaction times required. Ren and coworkers showed that 1,3-dialkylimidazolium halide-based ionic liquids can be used as solvents in the Rosemund von Braun reaction [37]. Complete conversion, based on GC-MS analysis, was achieved after 24 h at 90 °C. When using microwave irradiation and ionic liquid as a solvent, Leadbeater and coworkers showed the reaction times could be reduced to between 3 and 10 min [38]. Under the optimized reaction conditions, 2 equiv. CuCN and 1 equiv. aryl halide were rapidly heated to 200 °C in [i-PrMIM]Br as solvent. Representative results are collected in Table 7.3. The microwave method works as well as the conventional method for a range of aryl iodide and aryl bro-... 

Tab. 7.3. Rosemund von Braun reaction using ionic liquids and microwave heating.

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See also in sourсe #XX -- [ ]

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