Synthesis of 3-(arylmethylene)isoindolin-1-ones from ynamides by Heck–Suzuki–Miyaura domino reactions. Application to the synthesis of lennoxamine

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.

Formal Total Syntheses of (+)- and (-)-Aspidophytine from a Common, Homochiral Precursor

A formal total synthesis of (-)-aspidophytine (2), a key substructure associated with the heterodimeric indole alkaloid haplophytine (1) and itself a natural product, has been established by employing the homochiral and enzymatically derived cis-1,2-dihydrocatechol 8 as a starting material. Specifically, compound 8 has been converted into the pentacyclic product 26, an advanced intermediate associated with a previously reported synthesis of aspidophytine (2). Simple modifications to the reaction sequence have also allowed for the identification of a synthetic pathway leading from dihydrocatechol 8 to (+)-aspidophytine (ent-2).

Green novel multicomponent synthesis and biological evaluation of new oxazolopyrazoloazepines and reduction of nitrophenols in the presence of Ag/Fe3O4/ZnO@MWCNT MNCs

In this research, new derivatives of oxazolopyrazoloazepines were synthesized in high yields using multicomponent reaction of anilines, oxalylchloride, alkyl bromides, activated acetylenic compounds, hydrazine and ethyl bromopyruvate in the presence of Ag/Fe₃O₄/ZnO@MWCNT magnetic nanocomposite (MNCs) as a high-performance magnetic catalyst in ionic liquid at room temperature. The Ag/Fe₃O₄/ZnO@MWCNT magnetic nanocomposites (MNCs) were synthesized using 1-octhyl-3-methyl imidazolium bromide ([OMIM]Br) as a stabilizer and soft template. Also, the catalytic activity of the Ag/Fe₃O₄/ZnO@MWCNT MNCs was evaluated in reduction of organic pollutants such as 4-nitrophenol (4-NP) in water at mild conditions. The results indicated that the biosynthesized nanocomposites (NCs) have high catalytic activity for organic pollutants within few seconds. Because of having benzazepine nucleus in the synthesized compounds, we investigate antioxidant property of some synthesized oxazolopyrazoloazepines by diphenyl-picrylhydrazine radical trapping and power of ferric reduction experiment. Short time of reaction, high yields of product, easy separation of catalyst and products are some advantages of this procedure.

Base-Promoted Cascade Reactions for the Synthesis of 3,3-Dialkylated Isoindolin-1-ones and 3-Methyleneisoindolin-1-ones

Cascade reactions of ortho-carbonyl-substituted benzonitriles with ((chloromethyl)sulfonyl)benzenes as pronucleophiles led to new isoindolin-1-ones with a tetrasubstituted C-3 position or to (Z)-3-(sulfonyl-methylene)isoindolin-1-ones. The reactions start from readily available materials, are carried out under mild conditions, and do not require metal catalysis. Promoted only by the cheap and environmentally benign K₂CO₃ as the base, up to six elemental steps can be combined in a single pot. Hence, a sequential one-pot cascade/β-elimination/alkylation furnished useful intermediates for the synthesis of aristolactam natural products. The observed selectivity and the mechanism were investigated by DFT studies.

Production of benzazepine derivatives via four-component reaction of isatins: study of antioxidant activity

In current research, benzazepine derivative is synthesized via a new process of four-component reaction of isatin or its derivatives, α-haloketones, activated acetylenic compounds, isoquinoline and potassium fluoride/clinoptilolite nanoparticles (KF/CP NPs) in acidic solution of H2O2 in water at room temperature. Also, antioxidation property of some prepared benzazepines is investigated by employing trapping diphenyl-picrylhydrazine (DPPH) radical and ability of ferric reduction experiment. Among investigated compounds, compounds 5c have good results relative to BHT and TBHQ as standard antioxidant. Also, the Gram-positive and Gram-negative bacteria disk diffusion research is used for the confirmation of antimicrobial power of some prepared benzazepines. The achieved outcomes of disk diffusion experiment showed that these compounds avoided the growth of bacteria. Our procedure has a few benefits relative to reported method such as good rate of reaction, product with high efficiency, simple removal of catalyst from mixture of reaction. In the yield of the product, KF/clinoptilolite nanoparticles show a satisfactory recyclable activity.

Palladium-catalysed cyclisation of ynamides and propargyl tethered iodosulfonamides with boronic acids leading to benzosultams

An efficient and straightforward Pd-catalysed synthesis of diversely substituted sultams utilising ynamides and boronic acids is disclosed; toluene was found to be the most suitable solvent for this transformation. This strategy has been successfully applied to generate dihydrobenzo[d]isothiazole 1,1-dioxides and dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides. The advantages of this protocol are good functional group tolerance, broad substrate scope, high-yielding reaction and low catalyst loading to access benzofused sultams with five-/six-membered rings. The synthetic utility has been demonstrated by a gram-scale synthesis. A plausible catalytic cycle involving carbopalladation has been proposed for this transformation.

A Serendipitous One-Pot Cyanation/Hydrolysis/Enamide Formation: Direct Access to 3-Methyleneisoindolin-1-ones

A direct, one-pot conversion of 2'-haloacetophenones to 3-methyleneisoindolin-1-one scaffolds using CuCN as the sole reagent without the need for moisture-free or anaerobic conditions is reported. This serendipitously discovered transformation with a broad substrate scope provides a significantly different route towards these important scaffolds. The scope of the method has also been further extended towards the synthesis of three special scaffolds, which are analogous to various bio-active drugs.

Di-tert-butyl Ethynylimidodicarbonate as a General Synthon for the β-Aminoethylation of Organic Electrophiles: Application to the Formal Synthesis of Pyrrolidinoindoline Alkaloids (±)-CPC-1 and (±)-Alline

The reagent di-tert-butyl ethynylimidodicarbonate is demonstrated as a β-aminoethyl anion synthetic equivalent. It can be used to install ethyleneamine groups by exploiting its terminal alkyne reactivity with common organic electrophiles. Reactions exemplified with this terminal ynimide reagent include additions to imines, aldehydes, ketones, pyridinium salts, Michael acceptors, epoxides, and Pd-catalyzed Sonogashira couplings. Subsequent regioselective [3 + 2] cycloadditions of the alkynyl-imides (ynimides) generate N,N-di-Boc imide-functionalized triazole and isoxazole heterocycles. Reduction of the ynimides with Pd-catalyzed hydrogenation generates ethyleneimides with easily removable N,N-di-Boc-carbamate protecting groups, allowing for a flexible ynimide-based approach to ethyleneamine installation. The utility of this two-step aminoethylation strategy was demonstrated in the short formal syntheses of pyrrolidinoindoline alkaloids (±)-CPC-1 and (±)-alline. Analogously, the reagent (N,N,N')-tri-Boc 2-ethynylhydrazine serves as a β-hydrazinoethyl anion synthetic equivalent.

Synthesis of (Z)-β-(Carbonylamino)alkenylindium through Regioselective anti-Carboindation of Ynamides and Its Transformation to Multisubstituted Enamides

The regioselective anti-carboindation of ynamides by using InBr₃ and silylated nucleophiles was developed to synthesize (Z)-β-(carbonylamino)alkenylindiums. The X-ray crystallographic analysis of an alkenylindium suggested that the reaction proceeded in an anti-addition fashion. In contrast to reported syn-carbometalations of ynamides by using organometallics, a cooperation of InBr₃ and silylated nucleophiles to ynamides achieved an anti-addition, which was supported by DFT calculations. The scope of substrates included various ynamides and silylated nucleophiles, such as silyl ketene acetals and silyl ketene imines. The transformation of synthesized alkenylindiums by iodination, radical coupling, and Pd-catalyzed cross-coupling successfully afforded trisubstituted enamines with high regio- and stereoselectivities.

Enantioselective Synthesis of All-Carbon Quaternary Centers Structurally Related to Amaryllidaceae Alkaloids

Enantioselective synthesis of all-carbon quaternary centers remains a considerable challenge for synthetic organic chemists. Here, we report a two-step protocol to synthesize such centers including tandem cyclization/Suzuki cross-coupling followed by halocarbocyclization. During this process, two rings, three new C-C bonds and a stereochemically defined all-carbon quaternary center are formed. The absolute configuration of this center is controlled by the stereochemistry of the adjacent stereocenter, which derives from an appropriate enantioenriched starting material. Using this method, we synthesized polycyclic compounds structurally similar to Amaryllidaceae alkaloids in high enantiomeric excesses. Because these products resemble naturally occurring compounds, our protocol can be used to synthesize various potentially bioactive compounds.

Regioselective access of alkylidendibenzo[c,f]oxocine framework via cyclocarbopalladation/cross-coupling cascade reactions and reductive Heck strategy

Palladium-catalyzed dual strategies of cascade cyclocarbopalladation/cross-coupling of alkynes and a reductive Heck reaction have been developed to construct dibenzo[c,f]oxocine frameworks with tri- and tetra-substituted exo-cyclic alkenes with high stereo- and regio-control.

Synthesis of tricyclic 3-hydroxyisoindolin-1-ones via triethylamine-catalyzed domino reactions of electron-deficient alkynes with phthalimidomalonate derivatives

A triethylamine-catalyzed domino reaction between phthalimidomalonate derivatives and activated alkynes has been developed under mild conditions.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

A metal-free tandem ring-opening/ring-closing strategy for the heterocyclic conversion of benzoxazin-4-ones to oxazolines

A facile metal-free tandem ring-opening/ring-closing strategy was developed for the synthesis of oxazolines in good to excellent reaction yields under mild reaction conditions.

Ynamide carbopalladation: a flexible route to mono-, bi- and tricyclic azacycles

Bromoenynamides represent precursors to a diversity of azacycles by a cascade sequence of carbopalladation followed by cross-coupling/electrocyclization, or reduction processes. Full details of our investigations into intramolecular ynamide carbopalladation are disclosed, which include the first examples of carbopalladation/cross-coupling reactions using potassium organotrifluoroborate salts; and an understanding of factors influencing the success of these processes, including ring size, and the nature of the coupling partner. Additional mechanistic observations are reported, such as the isolation of triene intermediates for electrocyclization. A variety of hetero-Diels-Alder reactions using the product heterocycles are also described, which provide insight into Diels-Alder regioselectivity.

S3S63 Terminal Ynamides: Synthesis, Coupling Reactions and Additions to Common Electrophiles

Ynamides consist of a polarized triple bond that is directly attached to a nitrogen atom carrying a sulfonyl, an alkoxycarbonyl, an acyl or another electron withdrawing group. The triple bond polarization renders ynamides broadly useful building blocks with synthetic opportunities that go far beyond traditional alkyne chemistry. The versatile reactivity of ynamides in cycloadditions, cycloisomerizations, regioselective additions with various nucleophiles or electrophiles, ring-closing metathesis, and many other reactions has been investigated in detail during the past decades. A common feature of these methods is that the triple bond is consumed and either cleaved or transformed to a new functionality. The wealth of reports on these ynamide reactions is in stark contrast to the dearth of carbon-carbon bond formations that leave the triple bond of terminal ynamides intact. The recent introduction of effective synthetic methods for the preparation of terminal ynamides has set the stage to fully explore the synthetic potential of this intriguing class of compounds. This digest letter summarizes the most effective routes to terminal ynamides and the current state of selective nucleophilic addition, substitution and coupling reactions, including the first examples of asymmetric synthesis.

Palladium-catalyzed Csp2–H carbonylation of aromatic oximes: selective access to benzo[d][1,2]oxazin-1-ones and 3-methyleneisoindolin-1-ones

A selective palladium-catalyzed carbonylation of Csp²–H bonds with aromatic oximes for the synthesis of benzo[d][1,2]oxazin-1-ones and 3-methyleneisoindolin-1-ones has been developed.

Synthesis of a novel polycyclic ring scaffold with antimitotic properties via a selective domino Heck-Suzuki reaction

The synthesis of a previously undescribed sp3-rich 6-5-5-6 tetracyclic ring scaffold using a palladium catalysed domino Heck-Suzuki reaction is reported. This reaction is high-yielding, selective for the domino process over the direct Suzuki reaction and tolerant towards a variety of boronic acids. The novel scaffold can also be accessed via domino Heck-Stille and radical cyclisations. Compounds based around this scaffold were found to be effective antimitotic agents in a human cancer cell line. Detailed phenotypic profiling showed that the compounds affected the congression of chromosomes to give mitotic arrest and apoptotic cell death. Thus, a novel structural class of antimitotic agents that does not disrupt the tubulin network has been identified.

Palladium nanoparticles in glycerol: a clear-cut catalyst for one-pot multi-step processes applied in the synthesis of heterocyclic compounds

Palladium/TPPTS nanoparticles in glycerol represent a versatile catalyst leading to a large variety of heterocycles through domino/sequential one-pot approaches.

Ring enlargement reaction of C,N-cyclic-N'-acyl azomethine imines with sulfonium ylide: an efficient synthesis of 3-benzazepine derivatives

Highly efficient formation of 3-benzazepine derivatives has been achieved, based on the ring expansion reaction of C,N-cyclic-N'-acyl azomethine imines with sulfonium ylide generated in situ from the corresponding sulfonium salt. The reactions proceeded smoothly to afford the tricyclic 3-benzazepine derivatives in good to high yields. A wide range of C,N-cyclic N'-acyl azomethine imines were applicable to this reaction.