Studies on Pyrazines; 38: [1] Acylation of Bromopyrazines and 2-Bromopyridine via Copper-Cocatalytic Stille Reaction

Abstract

Synthesis of acetylpyrazines 3 and propionylpyrazines 5 was achieved by copper-cocatalytic Stille reaction of bromopyrazines 1 with tributyl(1-ethoxyalkenyl)tin and then acidic hydrolysis. The optimal reaction conditions involve the combination of 15 mol% CuI with 5 mol% of PdCl₂(Ph₃P)₂. Similarly, 2-acylpyridines and propionylbenzenes were prepared from the corresponding aryl bromides.

Key words

cross-coupling - copper(I) iodide - organotin compounds - pyrazinyl ketones - acylpyridines

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11

The Cu-cocatalytic coupling of 1a was hardly impeded in the presence of 1 equivalent of acetophenone, which provided a 90 % yield of 5a.