Synthesis of saturated 1,4-benzodiazepines via Pd-catalyzed carboamination reactions

Synthetic aspects of 1,4- and 1,5-benzodiazepines using o-phenylenediamine: a study of past quinquennial

Benzodiazepines, seven-membered heterocyclic compounds having two nitrogen atoms at different positions, are ruling scaffolds in the area of pharmaceutical industry. They act as cardinal moieties in organic synthesis as well as in medicinal chemistry. Among the different benzodiazepines, 1,4- and 1,5-benzodiazepines play a far-reaching role in the field of biological activities such as anticonvulsion, anti-anxiety, sedation, and hypnotics. In the past few decades, researchers have conducted a lot of work on these moieties and developed broad, valuable, and significant approaches for their synthesis. In this review article, we recapitulate the systematic synthetic strategies of 1,4- and 1,5-benzodiazepines using o-phenylenediamine as a precursor over the past five years (2018-2022). This article will be helpful for scientists and researchers to examine and explore novel and efficient methods for the synthesis of these biologically active moieties.

Enantioenriched α-Vinyl 1,4-Benzodiazepines and 1,4-Benzoxazepines via Enantioselective Rhodium-Catalyzed Hydrofunctionalizations of Alkynes and Allenes

Benzofused seven-membered heterocycles such as 1,4-benzo[e]diazepines (1,4-BZDs) and 1,4-benzo[e]oxazepines (1,4-BZOs) were efficiently synthesized by Rh-catalyzed hydrofunctionalization of internal alkynes and allenes in good to excellent yields. The asymmetric hydroamination of (aminomethyl)anilines gave rise to 3-vinyl-1,4-BZDs with excellent enantioselectivities. Orthogonal N-deprotection of 1,4-BZDs allowed an easy entry to an advanced pyrrolobenzodiazepine metabolite of the V₂-receptor antagonist Lixivaptan.

Palladium(0)-catalysed regioselective cyclisations of 2-amino(tosyl) benzamides/sulphonamides: the stereoselective synthesis of 3-ylidene-[1,4]benzodiazepin-5-ones/benzo[f][1,2,5]thiadiazepine-1,1-dioxides

The Pd(0) catalysed cyclisation reactions between tert-butyl propargyl carbonates and 2-aminotosyl benzamides or sulphonamides deliver 1,4-benzodiazepin-5-ones or sultam derivatives, key components of many biologically active compounds. But 2-amino benzamides/sulphonamides require propargyl carbonates substituted at acetylenic carbon to undergo the reaction resulting in the stereoselective formation of the said products.

Metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates at room temperature

Herein, we describe the novel reactivity of hexafluoroisopropyl 2-aminobenzoates. The metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature. These procedures feature good functional group tolerance, mild reaction conditions, and excellent yields. The newly formed products can readily be converted to other useful N-heterocycles. Moreover, the products and their derivatives showed potent anticancer activities in vitro by MTT assay.

A metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature.

Palladium-Catalyzed Benzodiazepines Synthesis

This review is focused on palladium-catalyzed reactions as efficient strategies aimed at the synthesis of different classes of benzodiazepines. Several reaction typologies are reported including hydroamination, amination, C–H arylation, N-arylation, and the Buchwald–Hartwig reaction, depending on the different substrates identified as halogenated starting materials (activated substrates) or unactivated unsaturated systems, which then exploit Pd(0)- or Pd(II)-catalytic species. In particular, the use of the domino reactions, as intra- or intermolecular processes, are reported as an efficient and eco-compatible tool to obtain differently functionalized benzodiazepines. Different domino reaction typologies are the carboamination, aminoarylation, aminoacethoxylation, aminohalogenation, and aminoazidation.

One-Pot Synthesis of Seven-Membered Heterocyclic Derivatives of Diazepines Involving Copper-Catalyzed Rearrangement Cascade Allyl-Amination

A novel and efficient method has been proposed for the synthesis of 1,4-benzodiazepine-5-ones from o-nitrobenzoic N-allylamides by using molybdenyl acetylacetonate and copper(II) trifluoromethanesulfonate as catalysts in the presence of triphenylphosphine. This synthesis process involves nitrene formation, C-H bond insertion, C═C bond rearrangement, and C-N bond formation cascade reactions via copper- and molybdenum-catalyzed mediation. The method features a wide substrate scope and a moderate to high yield (up to 90%), exhibiting the possibility for practical applications.

Synthesis of Benzodiazepines Through Ring Opening/Ring Closure of Benzimidazole Salts

Pyrido-benzodiazepine derivatives are undoubtedly one of the most important structural motifs in the marketed drugs and the drug candidates. Commonly synthetic methods for construction of the benzodiazepine ring derivatives are based on the condensation reactions of two highly functionalized synthons. The development of synthesis for these compounds, however, is hampered by the regioselectivity and atom economy. In this work, a one-step synthesis of pyrido-benzodiazepine backbones and its analogues is achieved through continuous ring-opening hydrolysis of benzimidazole salts and intramolecular C-H bond activation. The reaction mechanism is explored by control experiments and density functional theory (DFT) calculations.

Green synthesis of 1,4-benzodiazepines over La2O3 and La(OH)3 catalysts: possibility of Langmuir–Hinshelwood adsorption

Adsorption of all the reactants and order of addition play a key role in the synthesis of 1,4-diazepines depicting possibility of Langmuir–Hinshelwood mechanism.

Copper-promoted synthesis of 1,4-benzodiazepinones via alkene diamination

A new method for the synthesis of 2-aminomethyl functionalized 1,4-benzodiazepin-5-ones is presented. The benzodiazepine core is well-known to interact with biological receptors and many pharmaceutical drugs are derived from this structure. The alkene diamination strategy is employed for the first time for the synthesis of 1,4-benzodiazepinones. In this reaction, copper(2-ethylhexanoate)₂ serves as promoter and a range of external amines can be coupled with 2-sulfonamido-N-allyl benzamides to generate the 1,4-benzodiazepinones in good yields.

Synthesis of 1,4-benzodiazepinones and 1,4-benzoxazepinones via palladium-catalyzed amino and oxyacetoxylation

Palladium-catalyzed amino and oxyacetoxylation have been developed to furnish 1,4-benzodiazepinones and 1,4-benzoxazepinones through the diheterofunctionalization of alkenes.

Recent Developments in Pd-Catalyzed Alkene Aminoarylation Reactions for the Synthesis of Nitrogen Heterocycles

This short review describes new developments in Pd-catalyzed aminoarylation reactions between aryl halides and alkenes bearing pendant nitrogen nucleophiles. These transformations provide a novel and powerful method for accessing numerous 3-, 5-, 6-, and 7-membered nitrogen heterocycles.

Intermolecular migratory insertion of unactivated olefins into palladium-nitrogen bonds. Steric and electronic effects on the rate of migratory insertion

We report a detailed examination of the effect of the steric and electronic properties of the ancillary ligand and the alkene reactant on the rate of migratory insertion of unactivated alkenes into the palladium-nitrogen bond of isolated palladium amido complexes. A series of THF-bound and THF-free amidopalladium complexes ligated by cyclometalated benzylphosphine ligands possessing varied steric and electronic properties were synthesized. The THF-free complexes react with ethylene at -50 °C to form olefin-amido complexes that were observed directly and that undergo migratory insertion, followed by β-hydride elimination to generate enamine products. The effect of the steric properties of the ancillary ligand on the binding of the alkene and the rate of migratory insertion were evaluated individually. The relative binding affinity of ethylene vs THF is larger for the less sterically hindered complex than for the more hindered complex, but the less hindered complex undergoes the insertion of ethylene more slowly than does the more hindered complex. These two changes in relative equilibrium and rate constants cause the rates of reaction of ethylene with the two THF-ligated species having different steric properties to be similar to each other. Reactions of the complexes containing electronically varied ancillary ligands showed that the more electron-poor complexes underwent the migratory insertion step faster than the more electron-rich complexes. Reactions of a THF-ligated palladium-amide with substituted vinylarenes showed that electron-poor vinylarenes reacted with the amido complex slightly faster than electron-rich vinylarenes. Separation of the energetics of binding and insertion indicate that the complex of an electron-rich vinylarene is more stable in this system than the complex of a more electron-poor vinylarene but that the insertion step of the bound, electron-rich vinylarene is slower than the insertion step with the bound, electron-poor vinylarene.