Synthesis of N-Acylimines and Related Derivatives

N-Acylimines represent a class of compounds in which an imine (C=N) functionality is directly bonded to an acyl moiety, combining the reactivity of imines with the stabilising effect of adjacent carbonyl groups. These entities serve both as synthetically versatile intermediates and as direct electrophiles in α-amidoalkylation, cyclisation and heteroatom-transfer reactions. Traditional approaches to N-acylimines involve the condensation of acylated amines with aldehydes or ketones under dehydrating conditions, often requiring acid catalysis. In recent years, alternative strategies have emerged, notably the use of bench-stable precursors—such as 1-aminoalkyltriarylphosphonium salts—that release N-acyliminium-type cations under mild or catalyst-free conditions. These developments have enabled more efficient, high-yielding processes, including one-pot multicomponent couplings and solvent-free protocols. The global significance of these methods spans the synthesis of bioactive molecules, advanced materials and chiral building blocks, underpinning advances in pharmaceutical discovery and sustainable chemical manufacture.

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Synthesis of N-Acylimines and Related Derivatives publication trend

The graph below shows the total number of articles in synthesis of n-acylimines and related derivatives across all publications each year (not limited to Nature Index journals).

Technical terms

N-Acylimine: An imine (C=NR) in which the nitrogen atom bears an acyl substituent, combining electrophilic character with stabilisation from the adjacent carbonyl.

N-Acyliminium ion: A positively charged species formed by protonation or leaving-group departure at an N-acylimine, featuring a conjugated C=N+ centre that is highly electrophilic towards nucleophiles.

α-Amidoalkylation: A reaction in which an amide or acylated amine precursor generates an α-amidoalkyl cation that undergoes C–C or C–heteroatom bond formation at the carbon adjacent to nitrogen.

1-Aminoalkyltriarylphosphonium salt: A phosphonium reagent bearing an N-acylated aminoalkyl group; acts as a stable surrogate for N-acyliminium cations upon Cα–P bond cleavage.

References

1. 1-(N-Acylamino)alkyltriarylphosphonium Salts with Weakened Cα-P+ Bond Strength—Synthetic Applications. Molecules (2018).
2. Synthesis of N‑Protected 1‑Aminoalkylphosphonium Salts from Amides, Carbamates, Lactams, or Imides. The Journal of Organic Chemistry (2021).
3. 1-Aminoalkylphosphonium Derivatives: Smart Synthetic Equivalents of N-Acyliminium-Type Cations, and Maybe Something More: A Review †. Molecules (2022).