Regio- and Stereoselective Synthesis of Isoindolin-1-ones through BuLi-Mediated Iodoaminocyclization of 2-(1-Alkynyl)benzamides

Metal-Free Synthesis of 4-Bromoisoquinolines through Brominative Annulation of 2-Alkynyl Arylimidate Using In Situ-Generated Transient Bromoiodane

Herein, we report the in situ-generated transient bromoiodane-mediated brominative annulation of 2-alkynyl arylimidate for the synthesis of 4-bromoisoquinolines at room temperature. Using a simple hypervalent iodine reagent PIDA as a mild oxidant and potassium bromide as the halogen source, a broad range of valuable 4-bromoisoquinolines can be synthesized in excellent yields. The reaction features readily available chemicals, mild metal-free conditions, and high functional group tolerance, providing an efficient alternative for the construction of halogenated isoquinolines.

Exploring isoindolin-1-ones as potential CDK7 inhibitors using cheminformatic tools

In women who die from cancer, breast cancer is the most common cause of death. The development of small molecular scaffolds as specific Cyclin-dependent kinase (CDK) inhibitors is a promising strategy in the discovery of anti-breast cancer drugs. Isoindolin-1-ones are heterocyclic compounds with useful therapeutic properties. In this study, a library of 48 isoindolinones has been virtually screened by molecular docking that showed high binding affinity up to - 10.1 kcal/mol and conventional hydrogen bonding interactions with active amino acid residues of CDK7. The molecular dynamics simulation (MDS), fragment molecular orbital (FMO), density functional theory (DFT), and pharmacokinetics studies of the best two docked scored ligands 7 and 14 have been studied. Examining the ligand root mean square deviation and hydrogen bonding occupancy of the 100 ns MDS trajectory, both ligands 7 and 14 showed docked pose stability. FMO calculations displayed that LYS139 and LYS41 are majorly contributing to the binding interactions with ligands 7 and 14 in the docked poses. DFT studies of ligands 7 and 14 showed high values of global softness and low values of global hardness and chemical potential thus displaying chemically reactive soft molecules and this influences their anti-cancer activity. Our hits exhibited superior qualities to known CDK7 inhibitors, according to the comprehensive pharmacokinetic parameters that were predicted. The results indicate that isoindolin-1-one moieties are good candidates for anti-cancer action and could serve as effective CDK7 inhibitors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00225-0.

Cyclization-Carbonylation of 2-Alkynyl Primary Benzamides using p-Benzoquinone under Neutral Conditions

A palladium-catalyzed cyclization-carbonylation of 2-alkynyl primary benzamides 1 afforded methyl 3-substituted 1-methoxyisoquinoline-4-carboxylates 6 in good to moderate yields. In the case of mesylate 1r, 12 was obtained directly via a cyclization-carbonylation-cyclization cascade. Compounds 6 were converted to isoquinolin-1(2H)-ones 8 in good yields under microwave irradiation. In the case of the mesylate 6q, tricyclic isoquinolinone 10 was obtained in good yield. The reactions of thiophene-2-carboxamide derivatives also proceeded well.

Synthesis of Tetrasubstituted Enamines through Borane-Catalyzed Hydrogenations

This paper describes a B(C6F5)3-catalyzed hydrogenation of β-substituted α,β-unsaturated imines by using as low as 0.2 mol % catalyst. A variety of tetrasubstituted enamines were afforded in 95-99% yields. It provides an efficient and facile way without the need for column chromatography purification.

A Convenient Synthesis of Novel Isoxazolidine and Isoxazole Isoquinolinones Fused Hybrids

Isoxazolidine, isoxazole, and isoquinolinone rings are present in the structure of several natural products and/or pharmaceutically interesting compounds. In this work, facile and efficient pathways have been developed for the preparation of fused frameworks bearing those heterocycles. The successful approaches for both isoxazolidine/isoquinolinone and isoxazole/isoquinolinone hybrid syntheses relied initially on 1,3-dipolar cycloadditions of nitrones and nitrile oxides to indenone and 2-propargylbenzamide, respectively. The construction of the isoquinolinone lactam system followed by performing a selective Schmidt reaction for isoxazolidine derivatives (two steps overall), whereas the isoxazole lactams were reached via an Ullmann-type cyclisation (three steps overall). Key observations were made regarding the stereo- and regioselectivities of the reactions employed, and small libraries of the targeted hybrids were prepared, demonstrating the general applicability of these strategies.

Synthesis of pyrimidine-fused skeletons through copper-catalyzed consecutive Sonogashira coupling and aminocyclization

A copper-catalyzed sequence involving a Sonogashira coupling reaction and 5-exo-dig aminocyclization between a terminal alkyne and a 2-(2-bromophenyl)pyrimidine analog based on six-membered rings is presented. This protocol provides a controlled and modular approach to access a variety of synthetically useful pyrimidine-fused skeletons with high efficiency, broad substrate scope, and excellent functional group compatibility. Under acidic conditions, the (Z)-configuration of products spontaneously converts into (E)-9-benzylidene-1,9-dihydro-11H-pyrazolo[4',3':4,5]pyrimido[2,1-a]isoindol-11-ones.

Base-Promoted 5-exo-dig Cyclization of o-Alkynylamides or 2-En-4-ynamides with CO2 toward Fully Substituted Acrylates

A base-promoted sequential cyclization and carboxylation of o-alkynylamides or 2-en-4-ynamides with CO₂ has been achieved with high efficiency, stereoselectivity, and regioselectivity. This approach begins with 5-exo-dig cyclization followed by trapping the resulting vinyl anion with CO₂ and MeI, which provides a convenient access to diverse cyclic and fully substituted acrylates with CO₂ as the carboxylic source.

Electrochemical synthesis of isobenzofuran-1-imines using oxidative halocyclization of o-alkynylbenzamides

Electrochemical oxidative 5-exo-dig-oxo-halocyclization of o-alkynylbenzamides was achieved using readily available NaX (X = Cl, Br and I) salts under mild reaction conditions. The use of a cheap and highly stable sodium halide as a halide ion source is impressive for the synthesis of a variety of halogenated isobenzofuran-1-imines. This electrochemical protocol shows regioselectivity and excellent conversion to isobenzofuran-1-imines in good yields without the use of stoichiometric amounts of oxidants and transition metal catalysts.

Iron-catalyzed stereoselective haloamidation of amide-tethered alkynes

In this work, by using N-methoxybenzamides as efficient acyl nitrene precursors, an iron-catalyzed formal cis-haloamidation of alkyne is reported. Without assistance of additives, the reaction worked well in the presence of 50 mol% FeCl3 or FeBr3, leading to a series of chloro/bromo-containing isoindolin-5-ones with high efficiency and wide reaction scope. In the reaction, the iron-facilitated haloamidation proceeds through a halo anion-participating concerted [3+2] cyclization to release the final products. The key intermediate ferric acyl nitrene A is generated in situ from a formal removal of MeOH.

Ring Opening/Site Selective Cleavage in N-Acyl Glutarimide to Synthesize Primary Amides

A LiOH-promoted hydrolysis selective C-N cleavage of twisted N-acyl glutarimide for the synthesis of primary amides under mild conditions has been developed. The reaction is triggered by a ring opening of glutarimide followed by C-N cleavage to afford primary amides using 2 equiv of LiOH as the base at room temperature. The efficacy of the reactions was considered and administrated for various aryl and alkyl substituents in good yield with high selectivity. Moreover, gram-scale synthesis of primary amides using a continuous flow method was achieved. It is noted that our new methodology can apply under both batch and flow conditions for synthetic and industrial applications.

Functionalisation of isoindolinones via a calcium catalysed Hosomi-Sakurai allylation

A rapid and functionally tolerant calcium catalysed Hosomi-Sakurai reaction has been realised. Employing 1 mol% calcium, allylated isoindolinones can be synthesised in high yields and the reaction is shown to be tolerant to a range of medicinally relevant functional groups including heterocycles. The synthetic utility of the reaction has been shown, and a plausible reaction mechanism is provided.

Theoretical Insight into the Mechanism and Origin of Divergent Reactivity in the Synthesis of Benzo-Heterocycles from o-Alkynylbenzamides Catalyzed by Gold and Platinum Complexes

This work presents a DFT study on the mechanism and origin of catalyst-controlled divergent reactivity in the synthesis of benzo-heterocycles from o-alkynylbenzamides by Au(I)/Pt(IV) catalysis. The results indicate that the transformations proceed via a nucleophilic cyclization process. In the Au(I) catalysis, the preferred O-attack mode mainly originates from the symmetry match in the dominant bond-forming interaction between the lone-pair orbital of carbonyl-O and the in-plane alkyne π* orbital, and the electronic property of the ligand controls the O-5-exo-dig/O-6-endo-dig selectivity. The preference for the N-attack mode in Pt(IV) catalysis is attributed to the stronger coordinate capability of carbonyl-O than amino-N in the substrate to PtCl₄, and the regioselective N-6-endo-dig or N-5-exo-dig cyclization depends on the stronger electrostatic interaction between the amino-N and alkynyl-C_β atoms. The theoretical results provide a fundamental understanding of why and how gold and platinum complexes catalyze the cyclization of o-alkynylbenzamides with different chemo- and regioselectivities.

Oxidative oxy-cyclization of 2-alkynylbenzamide enabled by TBAB/Oxone: switchable synthesis of isocoumarin-1-imines and isobenzofuran-1-imine

A TBAB-controlled switchable synthesis of isocoumarin-1-imine and isobenzofuran-1-imine from 2-alkynylbenzamide in water is described in this paper.

Silyl Group-Directed 6-exo-dig Iodocyclization of Homopropargylic Carbamates and Amides

Iodocyclization of silyl group-substituted homopropargylic carbamates and amides proceeded via 6-exo-dig mode to afford 6-vinylene-4,5-dihydro-1,3-oxazines in moderate to quantitative yields. This is the first report for silyl group-solely directed iodocyclization of alkynes utilizing the β-silyl effect. Under these mild reaction conditions, various functionalities such as secondary alcohol, acetal, urea, and sulfide were tolerated.

Ir(III)-Catalyzed Stereoselective Haloamidation of Alkynes Enabled by Ligand Participation

Described herein is the application of a strategy of ligand participation for the Ir-catalyzed imido transfer into alkynes. On the basis of a stoichiometric [3 + 2] cycloaddition of Cp*Ir(III)(κ²- N, O-chelate) with alkynyl dioxazolone, a catalytic haloamidation was developed for the first time by employing [Cp*IrCl₂]₂ precatalyst and NaX salts (X = Cl or Br) as practical halide sources to furnish synthetically versatile Z-(halovinyl)lactams with excellent stereoselectivity.

Approach to Chiral 1-Substituted Isoquinolone and 3-Substituted Isoindolin-1-one by Addition-Cyclization Process

An approach to access 1-substituted isoquinolones has been developed through the addition-cyclization of imines with Grignard reagents in the presence of 2,2'-dipyridyl. A number of substituted aromatic magnesium reagents were amenable to this process, and the desired products were obtained with excellent yields and outstanding diastereoselectivities ( dr > 99:1). The utility of this convenient approach is demonstrated by the formal synthesis of ( S)-cryptostyline II. Moreover, N-methylmorpholine (NMM) was found to be an effective additive for the formation of 3-substituted isoindolin-1-ones using one-pot addition-cyclization-deprotection of imine with Grignard reagents.

Highly regioselective, electrophile induced cyclizations of 2-(prop-1-ynyl)benzamides

We report an electrophile promoted, highly regioselective (∼100%) synthesis of 5-membered haloimidiates from 2-(1-alkynyl)benzamides under metal free conditions.