Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Pd(ii)-Catalyzed regioselective functionalization of antipyrines: synthesis of pyrazolono-maleimides and pyrazolono-quinones

A Pd(ii)-catalyzed direct functionalization reaction of the 4Csp²-H bond of antipyrine derivatives is reported. This metal-catalyzed reaction of antipyrines with maleimides provided an easy and efficient access to biologically important pyrazolonomaleimides. This catalytic system is also applicable for C-4 functionalization of the antipyrine ring with quinone derivatives.

Copper(ii)-catalyzed synthesis of multisubstituted indoles through sequential Chan–Lam and cross-dehydrogenative coupling reactions

Starting from arylboronic acids and ester (Z)-3-aminoacrylates, one-pot syntheses of diverse indole-3-carboxylic esters have been described through copper(ii)-catalyzed sequential Chan–Lam N-arylation and cross-dehydrogenative coupling (CDC) reactions. The initial Chan–Lam arylation can proceed in DMF at 100 °C for 24 h to give ester (Z)-3-(arylamino)acrylate intermediates in the presence of Cu(OAc)₂/tri-tert-butylphosphine tetrafluoroborate, a catalytic amount of myristic acid as the additive, KMnO₄ and KHCO₃. Sequentially, these in situ arylated intermediates can undergo an intramolecular oxidative cross-dehydrogenative coupling process in mixed solvents (DMF/DMSO = 2 : 1) at 130 °C to give C3-functionalized multi-substituted indole derivatives.

One-pot syntheses of diverse indole-3-carboxylic esters have been described through copper(ii)-catalyzed sequential oxidative Chan–Lam N-arylation and cross-dehydrogenative coupling (CDC) reaction.

Manganese(iii)-mediated selective phosphorylation of enamides: direct synthesis of β-phosphoryl enamides

Mn(iii)-Mediated radical oxidative selective phosphorylation ofN-styrylamides to afford β-phosphoryl enamides, which could be easily transformed to β-amino phosphonic acids, is described.

Supramolecular architecture in azaheterocyclic phosphonates. III. Structures of an ethyl phosphonamidate and an ethyl phosphonate

The novel crystal structures of ethyl (S)-P-(4-oxo-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-3-yl)-N-[(R)-1-phenylethyl]phosphonamidate, C20H20N3O3PS, I, and diethyl (4-isopropyl-2-oxo-3,4-dihydro-2H-benzo[4,5]thiazolo[3,2-a]pyrimidin-3-yl)phosphonate, C18H25N2O4PS, II, were characterized by X-ray diffraction analysis. The crystal packing of I is dominated by two infinite stacks composed of symmetry-independent molecules linked by distinctively different hydrogen-bond systems. The structure of II shows a ladder packing topology similar to those observed in related phosphorylated azaheterocycles. Structural studies are supplemented by calculations on the interactions stabilizing the molecular assemblies using the PIXEL method. Additionally, fingerprint plots derived from the Hirshfeld surfaces were generated for each structure to characterize the crystal packing arrangements in detail. The aromaticities of the heterocyclic moieties have been investigated using HOMA and HOMHED parametrization and compared with structures reported previously.

Copper-Catalyzed Synthesis of Multisubstituted Indoles through Tandem Ullmann-Type C-N Formation and Cross-dehydrogenative Coupling Reactions

Multisubstituted indoles were synthesized via a one-pot tandem copper-catalyzed Ullmann-type C-N bond formation/intramolecular cross-dehydrogenative coupling process at 130 °C in DMSO. The methodology allows practical and modular assembly of indoles in good to excellent yields from readily available aryl iodides and enamines.

Recent progress in the synthesis of phosphorus-containing indole derivatives

Phosphorus-containing indole derivatives represent a special class of phosphorus-containing nitrogen heterocycles. This review summarizes the recent progress in the synthesis of such compounds, briefly discusses the reaction mechanisms and challenges, and outlines the synthetic opportunities still open.

Brønsted acid-catalysed regiodivergent phosphorylation of 2-indolylmethanols to synthesize benzylic site or C3-phosphorylated indole derivatives

A Brønsted acid catalyzed highly regiodivergent phosphorylation of 2-indolylmethanols with diarylphosphine oxides has been established, which provides an efficient protocol for accessing benzylic site or C3-phosphorylated indole derivatives with structural diversity.