Main Group Metal‐Mediated Transformations of Imines

Abstract

Main‐group‐metal‐mediated transformations of imines have earned a valued place in the synthetic chemist's toolbox. Their versatility allows the simple preparation of various nitrogen containing compounds. This review will outline the early discoveries including metallation, addition/cyclisation and metathesis pathways, followed by the modern‐day use of imines in synthetic methodology. Recent advances in imine C−F activation protocols are discussed, alongside revisiting “classic” imine reactivity from a sustainable perspective. Developments in catalytic methods for hydroelementation of imines have been reviewed, highlighting the importance of s‐block metals in the catalytic arena. Whilst stoichiometric transformations in alternative reaction media such as deep eutectic solvents or water have been summarised. The incorporation of imines into flow chemistry has received recent attention and is summarised within.

Insights into LiAlH4 Catalyzed Imine Hydrogenation

“…As previously reported, catalytic reduction of tBuC(H)=NtBu is much more sluggish (Table 1, entry 7) [13] because the C=N bond in this bis-alkylated imineisn ot activated by conjugation with Ph. Under forced conditions, however,t he double addition product was formed and could be crystallized in the form of LiAlH 2 [N(tBu)CH 2 tBu] 2 •(TMEDA) (5). Despite two equivalents of TMEDAh ave been used, ac ontact-ion-pair with only one TMEDA ligand and an intimateA l(m-H) 2 Li contact crystallized ( Figure 1, Table 2).…”

“…Despite the requirement of elevated temperatures, main group metal-mediated imine transformations are of prime industriali mportance. [5] Although these applications are based on stoichiometric use of LiAlH 4 ,t he last decades have seen some interesting examples of LiAlH 4 (or related compounds) in catalysis. [6][7][8][9][10][11][12][13] During the development of early main group metal catalyzed imine hydrogenation, [14] we found that commercially availableL iAlH 4 can be used under relatively mild conditions in catalytic instead of stoichiometric quantities (2.5 mol %c atalyst loading, 1bar H 2 and 85 8C).…”

Introducing Water and Deep Eutectic Solvents in Organosodium Chemistry: Chemoselective Nucleophilic Functionalizations in Air

“…To this end, a 0.52 M solution of o-lithiated anisole was prepared by subjecting 1 b (0.65 mmol) to a bromo-lithium exchange with n-BuLi (0.65 mL, 2.0 M in hexanes) in hexane (0.6 mL) at 0 °C for 10 min. [24] After an additional stirring at RT for 20 min, 1.6 equiv (0.61 mL) of the resulting solution were rapidly spread out over a suspension of 2 a (0.2 mmol) either in water (1 mL) or in a ChCl/urea mixture (1 : 2 mol mol À 1 ) (1.0 g), while working at room temperature, under air and vigorous stirring. Adduct 4 a again formed in good yields: 84 % in water and 86 % in DES ( 1 H NMR analysis).…”

Reactions of cobalt(ii) chloride and cobalt(ii) acetate with hemisalen-type ligands: ligand transformation, oxidation of cobalt and complex formation. Preliminary study on the cytotoxicity of Co(ii) and Co(iii) hemisalen complexes

“…[12][13][14][15][16][17] Schiff bases feature exciting properties related to the simultaneous presence of proton-donor and proton-acceptor groups, the possibility of formation of inter-and intramolecular hydrogen bonds and participation in proton transfer processes. [16][17][18][19][20][21][22][23][24] Based on these properties, imines are widely used in organic processes, such as the addition of organometallic reagents to C]N bond, 16,20,21,25,26 hydrolysis to aldehyde/ketone and amine, 21,27,28 self-condensation, 25,[29][30][31][32] complexation reactions with both main groups and transition metals, 21,33,34 pHand metal ion-dependent hydrolysis on the metal center during the formation of the coordination complex. [35][36][37][38] In our previous work, we described the immediate hydrolysis of the imine HL1 (2-methoxy-6-(E-2-pyridyliminomethyl)phenol) in the presence of nickel cations.…”