The Media in Black and White

Pd-Catalyzed C–N Coupling Reactions Facilitated by Organic Bases: Mechanistic Investigation Leads to Enhanced Reactivity in the Arylation of Weakly Binding Amines

“…The addition of a substoichiometric amount (4 mol% Pd) of precatalyst (COD(Pd-AlPhos) 2 ) to a solution of 1 in THF (Figure 3, A) showed only one signal (118.1 ppm) consistent with the oxidative addition (OA) complex (Figure 1, II), which has been previously isolated and reported. 9 Next, addition of aniline to this solution resulted in the complete consumption of the OA complex and the formation of a species exhibiting a broad resonance at 77 ppm (Figure 3, B), which we believe to be the aniline-bound OA complex (Figure 1, III) based on previous experiments involving aliphatic amines. 9 Addition of DBU to this solution initiated the catalytic reaction and resulted in the formation of a new, sharp resonance at 70.1 ppm (Figure 3, C) .…”

“…9 Next, addition of aniline to this solution resulted in the complete consumption of the OA complex and the formation of a species exhibiting a broad resonance at 77 ppm (Figure 3, B), which we believe to be the aniline-bound OA complex (Figure 1, III) based on previous experiments involving aliphatic amines. 9 Addition of DBU to this solution initiated the catalytic reaction and resulted in the formation of a new, sharp resonance at 70.1 ppm (Figure 3, C) . This spectrum exhibits a chemical shift equivalent to that of a separately prepared DBU-bound OA complex (Figure 3, D), providing evidence that this base-bound Pd species is likely the resting state of the catalyst during the catalytic reaction.…”

“…Under our previously reported reaction conditions using soluble amine bases, 9 the coupling reactions of secondary amines with aryl halides or triflates resulted in low or no formation of the desired product. For example, the reaction of 1 and indoline resulted in a 10% yield of the desired product (Table 1, 1a) when heated to 60 °C in 2-methyl tetrahydrofuran in the presence of an AlPhos-supported Pd catalyst and DBU.…”

“…Specifically, our laboratory recently reported the use of the soluble organic base 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) in the coupling of aryl amines, amides, and primary aliphatic amines with a variety of aryl (pseudo)halides. 9 While the soluble organic bases have mitigated the operational issues and functional group incompatibilities associated with inorganic bases, little is known about their mechanistic role at the molecular level. Therefore, better understanding of these catalytic systems would provide fundamental information on this emerging area of homogenous catalysis.…”

The Enemy Within: The Long Civil Rights Movement and the Enemy Pictures

“…In the 1980s, new culturalist approaches tended to emphasize the viewer's role (Hall 1973;McQuail 1983;Morley & Hall 1986;Scannell 1994). With regards to the Civil Rights Movement, the role of the media in presenting a distorted vision of the events of the 1950s and 1960s has been extensively analyzed (Dennis 2011;Ward 2001;Martindale 1986;Weill 2002).…”