Abstract
Palladium-catalyzed the Sonogashira coupling reaction of 3-halogen-2-aminopyridines 1 with terminal alkynes 2 afforded the corresponding 21 target products 3a-3u in the presence of palladium catalyst. The structure of target products 3a-3u was confirmed and characterized by 1H NMR, 13C NMR, and HRMS. The influences of different kinds of catalyst loading, bases, substrates and temperature were also investigated. Under the optimized conditions, including 2.5 mol% Pd (CF3COO)2, 5 mol% PPh3 and 5 mol% CuI as additive, 1 mL Et3N, substrate 1 with terminal alkynes 2 for the cross-coupling reactions at 100°C for 3 h in DMF afforded the corresponding products of 2-amino-3-alkynylpyridines 3 in moderate to excellent yields (72% - 96%). The present methodology has provided an effective synthetic method including operational convenience, high efficiency and wide-application.
Highlights
Sonogashira reaction is the sp-sp2 carbon cross-coupling reaction of terminal alkynes with aryl halides or alkenyl halide
Under the optimized conditions, including 2.5 mol% Pd (CF3COO)2, 5 mol% PPh3 and 5 mol% CuI as additive, 1 mL Et3N, substrate 1 with terminal alkynes 2 for the cross-coupling reactions at 100 ̊C for 3 h in dimethyl formamide (DMF) afforded the corresponding products of 2-amino-3alkynylpyridines 3 in moderate to excellent yields (72% - 96%)
The Sonogashira reaction has been widely used in the synthesis of substituted alkynes and conjugated alkynes [13] [14] [15] [16]
Summary
Sonogashira reaction is the sp-sp carbon cross-coupling reaction of terminal alkynes with aryl halides or alkenyl halide. This reaction is one of the most effective methods to form new carbon-carbon bonds [1]-[9]. As early as 1975, Heck [10], Cassar [11] and Sonogashira [12] independently discovered this reaction. After nearly 40 years, it has gradually known by people and become an important name reaction. The Sonogashira reaction has been widely used in the synthesis of substituted alkynes and conjugated alkynes [13] [14] [15] [16].
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