Search

Research has been conducted on the preparation of the conformationally restricted nicotinoid from D- and L-glutamic acid. The pyroglutamic acid derivative coupling with ortho-lithiated 4-chloropyridine is described.

1,3,5-Triazinanes, as a kind of versatile building block, are applied in the synthesis of chromeno[2,3- d ]pyrimidin-5-one derivatives via two different reaction modes, which perfectly exhibits the powerful function of 1,3,5-triazinane as a three-atom synthon along with the structure variation of another substrate. The two annulation reactions proceed under mild conditions and bear broad substrate scope and high yield.

A microwave-promoted multicomponent reaction of 3-formylchromones, amines, and paraformaldehyde was achieved under catalyst-free and solvent-free conditions, delivering 5 H -chromeno[2,3- d ]pyrimidin-5-one derivatives in good to excellent yields via an unexpected annulation pathway, which further expanded the synthetic application of paraformaldehyde as a C1 building block.

We have developed cobalt-catalyzed, bidentate 2-(1-methylhydrazinyl)pyridine (MHP)-directed C( sp 2 )-H alkylation/annulation of benzoic hydrazides with various alkenes. Notably, diverse cyclopenta[ c ]isoquinolinones and dihydroisoquinolinones were obtained via this functional group-tolerant protocol. The reaction can be performed on a gram scale while maintaining an excellent yield, and the directing group can be removed efficiently under mild conditions. Furthermore, density-functional theory (DFT) calculations provide an incisive understanding of the observed regioselectivities for different olefins.

Palladium-catalyzed C(sp 2 )-H arylation of ortho C-H bonds involving 2-(1-methylhydrazinyl)pyridine (MHP) as the directing group has been investigated. The reaction proceeds smoothly under an air atmosphere to generate biaryl derivatives in an environmentally friendly manner while tolerating a wide range of functional groups. Notably, the directing group present in the product could be easily removed under mild reductive conditions., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The first asymmetric total synthesis of three picrinine-type akuammiline alkaloids, (-)-picrinine, (-)-scholarisine C, and (+)-5-β-methoxyaspidophylline, has been accomplished. The synthesis features an efficient acid-promoted oxo-bridge ring-opening and further carbonyl O-cyclization to assemble the furoindoline scaffold, an unusual Dauben-Michno oxidation to construct the requisite α,β-unsaturated aldehyde functionality, and a nickel-mediated reductive Heck reaction to forge the [3.3.1]-azabicyclic core.

The regioselective functionalization reaction of unprotected carbazoles with donor-acceptor (D-A) cyclopropanes has been demonstrated for the first time. With Sc(OTf) 3 as Lewis acid catalyst, the N-H functionalization of carbazoles takes place through a highly selective nitrogen-initiated nucleophilic ring opening reaction. Significantly, by engaging TfOH as Brønsted acid catalyst, a straightforward C-H functionalization at the 3-position of the unprotected carbazole proceeds via Friedel-Crafts-type addition. This strategy facilitates the diversity-oriented synthesis of carbazole-containing heterocycles and expands the novel application of D-A cyclopropanes.

The synthesis of 3,4-dihydro-2 H -1,3-thiazines from α-enolic dithioesters and 1,3,5-triazinanes has been achieved via a formal (3 + 3) annulation reaction under thermal conditions, where 1,3,5-triazinanes were utilized as three-atom synthons. This transformation is catalyst-free and additive-free.

Two reaction modes of pyridinium 1,4-zwitterionic thiolates with sulfenes generated in situ from alkanesulfonyl chlorides are described with DIPEA as the base. 3 H -1,2-Dithiole 2,2-dioxides could be obtained via a formal [3 + 2] pathway from alkylmethanesulfonyl chlorides, while 1,9a-dihydropyrido[2,1- c ][1,4]thiazines were obtained via a stepwise [(5 + 2) - 1] pathway from phenylmethanesulfonyl chlorides. Moreover, as an application, indolizines could be accessed via a stepwise {[(5 + 2) - 1] - 1} pathway, with 1,9a-dihydropyrido[2,1- c ][1,4]thiazines as the transient intermediates.

Pyridinium 1,4-zwitterionic thiolates, as a novel kind of sulfur-containing synthon, have been applied to the synthesis of 12a H -benzo[ f ]pyrido[1,2- d ][1,4]thiazepines and benzo[ b ]thiophenes. Benzopyridothiazepines were produced through a 1,5-dipolar cycloaddition reaction from pyridinium 1,4-zwitterionic thiolates with arynes, whereas benzothiophenes as side products were generated via a [3 + 2] cascade cyclization reaction. The [5 + 2] reaction mode of pyridinium 1,4-zwitterionic thiolates is disclosed for the first time.

A highly stereoselective synthesis of a spiro-cineole scaffold that contains four stereogenic centers from readily accessible 2-alkynylbenzaldehydes and styrenes under very mild reaction conditions was reported. This cascade reaction involves a Ag(I)-catalyzed alkyne cycloisomerization and oxa-[4 + 2]-cycloaddition to give an oxonium intermediate which subsequently undergoes a previously unexplored 1,2-alkyl migration to access highly strained spiro-2-oxabicyclo[2.2.2]octanes in high yields with excellent stereoselectivities.

A collective asymmetric total synthesis of lundurines A-C using l-pyroglutamic acid derived from the chiral pool is described. The key steps include a tandem reductive amination/lactamization sequence to introduce the pyrrolidinone ring, a palladium-catalyzed intramolecular direct C-H vinylation of indole to construct the crucial polyhydroazocine ring, and a Lewis acid promoted formal [3 + 2] cycloaddition/N 2 extrusion process to install the polysubstituted cyclopropyl ring.

A novel palladium-catalyzed decarboxylative coupling reaction of vinyl benzoxazinanones with arynes which may feature an intramolecular nucleophilic attack of an amino group at the central carbon of π-allylpalladium intermediate has been developed. The cis-5,5a,6,10b-tetrahydroindeno[2,1-b]indoles were generated in moderate to good yields. One key to the success of the present reaction was to achieve comparable rates for the palladium-catalyzed decarboxylation and aryne formation steps.

An efficient DABCO-catalyzed three-component formal [3 + 2 + 1] annulation, involving a Morita-Baylis-Hillman carbonate, a 1,3-ketoester, and a primary amine, leading to one-pot synthesis of substituted 4-aryl-1,2,3,4-tetrahydropyridines, has been developed. The densely functionalized products were generally obtained in good to excellent yields under mild conditions. The structures including the relative stereoconfigurations of the representative products were confirmed by X-ray diffraction analysis.

A chemoselective N-arylation reaction of 2-aminopyridine derivatives with arynes in good to excellent yields has been described. The N-arylation products could be further applied to the facile construction of benzoisoquinuclidines and isoquinuclidines as well as pyrido[1,2-a]benzimidazoles.

A novel Pd(II)-catalyzed cascade reaction has been developed that consists of a highly regio- and stereoselective oxa [4 + 2] cycloaddition reaction of o-alkynylbenzaldehydes and an intramolecular carboxylic group quenching of the in situ generated oxonium ion. This new reaction provides a one-step construction of the tetracyclic core structure of chaetophenol C from two simple starting materials. The developed chemistry was successfully applied to the first total synthesis of chaetophenol C and dozens of its analogues.

An efficient protocol for facile construction of spiro[indazole-3,3'-indolin]-2'-ones was developed via [3 + 2] dipolar cycloaddition of arynes with 3-diazoindolin-2-ones under mild conditions in excellent yields. Subsequent thermal isomerization of the spiro[indazole-3,3'-indolin]-2'-ones readily afforded indazolo[2,3-c]quinazolin-6(5H)-ones.

An asymmetric total synthesis of (-)-aspidophylline A has been accomplished. The key transformations include an asymmetric hydride transfer hydrogenation of an α,β-acetylenic ketone and a cationic gold(I)-catalyzed 6-exo-dig cyclization involving an alkynylindole/aminal formation cascade, which enables stereoselective establishment of the requisite quaternary carbon center.

The tricyclic intermediate 2 has been synthesized in eight steps from known compound 6 in 20% overall yield. As such, this constitutes a highly efficient formal synthesis of (±)-aplykurodinone-1. This synthesis features a unique, one-pot, intramolecular hetero-Pauson-Khand reaction (h-PKR)/desilylation sequence to expeditiously construct the tricyclic framework, providing valuable insights for expanding the scope and boundaries of h-PKR.

A Rh(II)-catalyzed dearomative intramolecular [3 + 2] dipolar cycloaddition involving the indolic C2-C3 carbon-carbon double bond has been developed. The reaction was launched from the triazole moiety within the substrate and proceeded efficiently under mild conditions. A wide range of functional groups could be tolerated. These features render the current reaction a highly useful tool for the synthesis of polycyclic indole alkaloids, as showcased by a rapid assembly of the core structure of Aspidosperma and the related alkaloids.

An efficient strategy for the one-pot synthesis of polysubstituted pyridines via a cascade reaction from aldehydes, phosphorus ylides, and propargyl azide is reported. The reaction sequence involves a Wittig reaction, a Staudinger reaction, an aza-Wittig reaction, a 6π-3-azatriene electrocyclization, and a 1,3-H shift. This protocol provides quick access to the polysubstituted pyridines from readily available substrates in good to excellent yields.

A novel and efficient protocol for the rapid construction of dibenzofuran motifs from 6-diazo-2-cyclohexenone and ortho-haloiodobenzene has been developed. The process involves one-pot Pd-catalyzed cross-coupling/aromatization and Cu-catalyzed Ullmann coupling.

An NBS-promoted allyloxyl addition-Claisen rearrangement-dehydrobromination cascade reaction has been developed. More than 20 substituted alkynylsulfonamides were reacted with allyl alcohols to generate (2Z)-2,4-dienamides in moderate to high yields. A mechanistic model has been proposed to account for the overall reaction sequence including the stereochemical outcome. Theoretical calculations suggested that a [3,3] sigmatropic rearrangement be the rate-limiting step.

A concise and efficient total synthesis of (±)-cephalosol has been completed (5 steps from known ester 5, 39% overall yield), featuring a Cu(II)-promoted haloisocoumarin formation and sequential Suzuki cross-coupling/intramolecular oxo-Michael addition., (© 2011 American Chemical Society)

A novel one-step assembly of tetrahydro-5H-indolo[3,2-c]quinolines from benzyl azides and indoles via a formal [4 + 2] cycloaddition is described. A cascade reaction sequence, which involves benzyl azide-to-iminium rearrangement followed by two sequential Pictet-Spengler reactions, generates the tetracycles in moderate to excellent yields. The current method is applicable to a broad substrate scope and holds significant potential in constructing polycyclic indolines with tertiary and/or quaternary carbon centers.

The first total synthesis of (±)-subincanadine C has been accomplished in a protecting-group-free fashion. This pentacyclic indole alkaloid was synthesized in six steps from the known intermediate 4, featuring Ni(COD)(2)-mediated intramolecular Michael addition as a key transformation., (© 2011 American Chemical Society)

A concise synthetic approach for constructing the oxapentacyclic framework of cortistatin A is described. The synthesis features a furan-oxyallyl [4 + 3] cycloaddition and double-intramolecular aldol reactions. In addition, an interesting core structure was obtained in 11 steps from furan by using our method.

Novel neonicotinoid analogues bearing a 1,4-dihydropridine scaffold were designed and synthesized by multicomponent reactions (MCRs) to enhance pi-pi stacking. The synthesized compounds were identified by (1)H NMR, (13)C NMR, high-resolution mass spectroscopy, and elemental analysis. Bioassay tests showed that some of them exhibited high insecticidal activities against pea aphid ( Aphis craccivora ).

The first total syntheses of (+)-villatamines A and B have been realized in six and five steps, respectively. The stereogenic center present in these two naturally occurring alkaloids should have an (S)-configuration based on our results.

A new and efficient samarium diiodide-promoted carbon-carbon bond fragmentation reaction of alpha-aminomethyl malonates, taking place normally at room temperature and generating the corresponding deaminomethylation products in 74-94% yields, is reported. The presence of the amino group is necessary for the success of the current transformation.