By Kevin H. Shaughnessy, Engelbert Ciganek, Rebecca B. DeVasher, Scott E. Denmark
The metal-catalyzed amination of aryl and alkenyl electrophiles has built right into a conventional method for the synthesis of usual items, lively pharmaceutical components, agricultural chemical compounds, and fabrics for molecular electronics. Copper catalysts advertise the coupling of quite a lot of nitrogen nucleophiles, together with amines, amides, and heteroaromatic nitrogen compounds with aryl and alkenyl halides. The reactivity profile of copper catalysts is complementary to that of palladium catalysts in lots of situations. Copper catalysts are powerful with much less nucleophilic nitrogen nucleophiles, comparable to amides and azoles, while palladium catalysts are more beneficial with extra nucleophilic amine nucleophiles. Copper is an enticing replacement to palladium as a result of its considerably lower price. moreover, excessive job palladium catalysts require pricey and infrequently air-sensitive ligands, while the trendy copper platforms use particularly reliable and cheap diamine or amino acid ligands. Copper-catalyzed C?N coupling reactions are tolerant of quite a lot of practical teams and feature been utilized to the synthesis of numerous advanced average items. major paintings has additionally been performed to appreciate the mechanism of those reactions. present mechanistic realizing of those methodologies is roofed during this monograph.
The contents of the ebook are taken from the excellent assessment of the subject within the natural Reactions sequence. optimum experimental stipulations for the amination of aryl and alkenyl halides with all sessions of nitrogen nucleophiles are provided. particular experimental tactics from the literature are supplied for the most important periods of copper-catalyzed C?N coupling reactions. A tabular survey of all examples of Cu-catalyzed arylation and alkenylation of nitrogen nucleophiles is gifted in 35 tables prepared by way of nitrogen nucleophile and electrophilic coupling partner.
The literature is roofed via December 2015 and offers three hundred contemporary citations to complement the 680 citations of the unique hardbound bankruptcy. those most recent literature references were accumulated in separate sections in keeping with the series of the tables within the tabular survey part. In all of the sections, the person citations were prepared in alphabetic order of the writer names.
Copper-Catalyzed Amination of Aryl and Alkenyl Electrophiles is meant to supply natural chemists with an available, yet precise, creation to this significant classification of adjustments.
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Additional info for Copper-Catalyzed Amination of Aryl and Alkenyl Electrophiles
By far the most commonly used copper salts are the Cu(I) halides, with CuI being the most generally useful precatalyst. 219 Copper(I) oxide has also been used as a catalyst precursor with results comparable to Cu(I) halides. 220 Copper(II) salts, such as CuO or CuSO4 , have also been successfully used under ligand-free conditions at high temperatures (150–200∘ ). 69,191,221 This lower activity is possibly due to slow reduction of the Cu(II) precatalyst to the Cu(I) active species. Copper(0) in the form of powder or bronze is commonly used in the traditional Ullmann conditions.
Careful studies comparing a wide range of ligand types for a given reaction class are rare. On the basis of comparisons of ligands and the data collected in the tables at the end of this chapter, certain trends can be deduced. Ligand-free catalysts are Diamines Amino Acids NHR NHR Me2N H N CO2H NHR NHR R H CDA Me DMCDA R H EDA Me DMEDA Pyridines R CO2H O,O Ligands OH R O 8-HOquin O OH OH N N N R H phen MeO 4,7-MeO2phen L-Pro DMG binol Figure 1. Common ligands for Cu-catalyzed C–N bond formation.
Arylation of amine ligands has been noted in some cases. 69,115,191 The arylated ligands appear to be ineffective at promoting the coupling reaction, which is why CDA and EDA are less effective than DMCDA or DMEDA in most cases. The more hindered secondary amine ligands are not prone to arylation. 192 This side reaction can be avoided by using N,N-dimethylglycine (DMG) or l-proline instead. 196 Using 2-isobutyrylcyclohexanone, selective N-arylation occurs to give product 50, whereas using 3,4,7,8-tetramethylphenanthroline as the ligand gives the O-arylation product 51 with high selectivity.