The Non-innocent Phenalenyl Unit: An Electronic Nest to Modulate the Catalytic Activity in Hydroamination Reaction

Abstract

The phenalenyl unit has played intriguing role in different fields of research spanning from chemistry, material chemistry to device physics acting as key electronic reservoir which has not only led to the best organic single component conductor but also created the spin memory device of next generation. Now we show the non-innocent behaviour of phenalenyl unit in modulating the catalytic behaviour in a homogeneous organic transformation. The present study establishes that the cationic state of phenalenyl unit can act as an organic Lewis acceptor unit to influence the catalytic outcome of intermolecular hydroamination reaction of carbodiimides. For the present study, we utilized organoaluminum complexes of phenalenyl ligands in which the phenalenyl unit maintains the closed shell electronic state. The DFT calculation reveals that the energy of LUMO of the catalyst is mainly controlled by phenalenyl ligands which in turn determines the outcome of the catalysis.

Cationic Gold Catalyst Poisoning and Reactivation

“…Although a linear correlation between the concentration of the catalyst and the initial rate data often exists when rate is plotted against concentration, numerous studies have shown that the regression line does not intersect with the origin (eq 1, A ≠ 0; also see Figure 1). If there is no background reaction, the rate should be 0 when the catalyst concentration is 0, so A (intercept) should also be 0, but this is not the case in many reactions ( A is usually less than 0), 1 indicating that a threshold catalyst concentration is required. Beyond vaguely implying some sort of catalyst poisoning, literature reports have not addressed the causes of this type of threshold.…”

Mechanistic insights and functionalization of alkynes in homogeneous gold catalysis.

“…For the second condition, we mixed propargyl amide 3-1 with catalytic amounts of Ph3PAu + OTf -and a strong acid, TfOH; the purpose of the strong acid was to make sure that the all the vinyl gold complex was protonated (Figure 14c). When monitored by 31 P NMR, both conditions ended up generating a single new peak at around 45 ppm (Figure 14b and Figure 14c). Hashmi and co-workers proposed that in the hydration of alkynes, a cluster of water molecules might act as proton shuttle to facilitate the protodeauration of a protonated vinyl gold intermediate.…”

“…Although a linear correlation between the concentration of the catalyst and the initial rate data often exists when rate is plotted against concentration, numerous studies have shown that the regression line does not intersect with the origin (eq 1, A≠0; also, see Figure 19). If there is no background reaction, the rate should be zero when the catalyst concentration is zero, so A (intercept) should be zero, but this is not the case in many reactions (A is usually less than zero), [30][31][32] indicating that a threshold catalyst concentration is required. Beyond implying some sort of catalyst poisoning, literature reports have not addressed the causes of this type of threshold.…”

“…should also be zero, but this is not the case in many reactions (A is usually less than zero), [30][31][32] indicating that a threshold catalyst concentration is required.…”

“…Although this phenomenon is ubiquitous in catalysis, relatively little effort has been spent on the investigation of this anomaly and the possible implications of this threshold phenomenon in catalysis. [30][31][32] During our research to improve the efficiency of gold catalysis, 29,[33][34][35][36] we found that this threshold phenomenon is common in gold-catalyzed reactions. We observed during our investigations that high gold affinity impurities (halides, bases) in solvents, starting materials, filtration or drying agents could affect the reactivity of the gold catalyst adversely (Scheme 4), which may significantly reduce the TON of cationic gold catalyzed reactions.…”