Synthesis of Methyl-Protected (±)-Chlorizidine A

The first total synthesis of the methyl-protected (±)-chlorizidine A has been achieved in 10 steps. Pd-catalyzed decarboxylative coupling and late-stage oxidation were utilized to construct the 5H-pyrrolo[2,1-a]isoindol-5-one scaffold. Samarium(II) iodide mediated Reformatsky reaction and intramolecular Mitsunobu reactions were efficiently applied for the synthesis of the 2,3-dihydropyrrolizine ring system. Chlorizidine A is highly prone to degradation; hence, methyl-protected (±)-chlorizidine A was prepared.

Synthesis of novel trifluoromethyl-substituted spiro-[chromeno[4,3-d]pyrimidine-5,1'-cycloalkanes], and evaluation of their analgesic effects in a mouse pain model

Herein we report the synthesis of twelve 2,5-substituted 4-(trifluoromethyl)-spirochromeno[4,3-d]pyrimidines (7-10), as well as an evaluation of their analgesic effect in a mouse pain model. The nine new chromeno[4,3-d]pyrimidines (7-9) were synthesized from the cyclocondensation reactions of three 2,2,2-trifluoro-1-(4-methoxyspiro[chromene-2,1'-cycloalkane]-3-yl)ethanones (3) containing 5-, 6- and 7-membered spirocycloalkanes, with some well-known amidine salts (4-6) [NH₂CR(NH)]-in which R=Me, Ph, and NH₂-at yields of 60-95%. Subsequently, three new 2-(pyrrol-1-yl)-4-(trifluoromethyl)-chromeno[4,3-d]pyrimidines (10) were obtained through a Clauson-Kaas reaction between the respective 2-(amino)-4-(trifluoromethyl)-chromeno[4,3-d]pyrimidines (9) and 2,5-dimethoxy-tetrahydrofuran. The analgesic evaluation showed that these 4-(trifluoromethyl)chromeno[4,3-d]pyrimidines (100mg/kg, p.o.) and Ketoprofen (100mg/kg, p.o.) significantly reduced capsaicin-induced spontaneous nociception. Moreover, the 2-pyrrolyl-spirocyclohexane derivative 10b (100 and 300mg/kg, p.o.) had an anti-allodynic effect comparable to Ketoprofen (100 and 300mg/kg, p.o.) in the arthritic pain model, without causing locomotor alterations in the mice. These results suggest that the compound 10b is a promising molecule for new analgesic drugs in the treatment of pathological pain, such as in arthritis.

Recent advances in synthetic facets of immensely reactive azetidines

Recent developments in synthetic strategies towards functionalized azetidines along with their versatility as heterocyclic synthons.

Metal-free C–H functionalization of 2H-imidazole 1-oxides with pyrrolyl fragments in the design of novel azaheterocyclic ensembles

Novel pyrrolyl-2H-imidazoles have been synthesizedviametal-free C–H/C–H coupling reactions under mild conditions and in good to excellent yields.

Synthesis of fused cyanopyrroles and spirocyclopropanes via addition of N-ylides to chalconimines

DABCO-ylides react as a one-carbon source with chalconimines to afford fused cyanopyrrolesvia[4 + 1] annulation and spirocyclopropanesvia[2 + 1] annulation.

1,5-Electrocyclization of conjugated azomethine ylides derived from 3-formyl chromene and N-alkyl amino acids/esters

A novel strategy has been developed for the synthesis of chromeno[3,4-b]pyrrol-4(3H)-one and substituted pyrrole derivatives. This is the first example of the preparation of highly substituted pyrrole derivatives from chromene-3-carboxaldehydes.

Trichloromethylthiolation of N-Heterocycles: Practical and Completely Regioselective

The first trichloromethylthiolation of a broad range of indoles and pyrroles is reported employing bench-stable N-trichloromethylthiosaccharin as reagent. This methodology is highly regioselective, exhibits high functional group tolerance, and provides access to two previously unknown classes of potentially bioactive compounds.

Microwave assisted aminocatalyzed [3 + 2] annulation between α-iminonitriles and succinaldehyde: synthesis of pyrrole-3-methanols and related polycyclic ring systems

A quick and highly efficient method for the synthesis of substituted pyrrole-3-methanols from α-iminonitriles and succinaldehyde under microwave irradiation is reported with good to high yields (up to 75%).

Recent developments in the group-1B-metal-catalyzed synthesis of pyrroles

Pyrroles are important synthetic targets as a result of their occurrence in numerous biologically active molecules, their important roles in diverse living processes, and their utility as versatile intermediates.

RhCl(PPh3)3-mediated C–H oxyfunctionalization of pyrrolido-functionalized bisazoaromatic pincers: a combined experimental and theoretical scrutiny of redox-active and spectroscopic properties

Non-trivial coordination mode of symmetrical NNN ligands with Rh(iii) leads to redox-active NNO-scaffolds via C(sp²)–H oxyfunctionalization at rt, opening an opportunity to juxtapose different redox-active domains.

Recent progress towards gold-catalyzed synthesis of N-containing tricyclic compounds based on ynamides

The recent advances in the gold-catalyzed construction of N-containing tricycles based on ynamides are reviewed by highlighting their specificity and applicability, and the mechanistic rationale.

Synthesis of novel imidazole-based triheterocycles via a domino Ugi/Michael reaction and silver-catalyzed heteroannulation

An efficient and diversity-oriented synthetic strategy for novel triheterocyclic imidazo-pyrrolo-pyrazine/diazepine/diazocine derivatives is elaborated.

Mild and ambient annulations for pyrrole synthesis from amines and arylacetaldehydes

A mild and ambient pyrrole synthesis via copper-catalyzed aerobic cyclization is described.

Enantioselective β-alkylation of pyrroles with the formation of an all-carbon quaternary stereocenter

A substitutionally and configurationally inert octahedral chiral-at-metal iridium complex is reported to be an efficient catalyst for the enantioselective Friedel–Crafts alkylation of 2,5-disubstituted pyrroles at the β-position using nitroacrylates as electrophiles.

Reaction of 2H-Azirine-Phosphine Oxides and -Phosphonates with Enolates Derived from β-Keto Esters

Cyclopenta[b]-pyrrole-2-phosphine oxides 4a and -phosphonates 4b,c are generated by the addition of cyclic enolates derived from ethyl 2-oxo-cyclopentanecarboxylate 2 to phosphorated 2H-azirines 1. However, the addition of enolate derived from acyclic 2-oxo-butanoate 10 to 2H-azirine phosphine oxide 1 led to vinylogous N-acyl-α-aminoalkyl phosphine oxides 12, involving the carbonyl group and the Cα of the keto ester 10. Ring closure of vinylogous derivative 12 in the presence of base afforded pyrrole-2-phosphine oxide 11. The addition of enolates derived from indenone-carboxylate 15 to 2H-azirines 1 led to the formation of functionalized N-substituted 1H-benzo[d]azepine derivatives 17.

Copper Catalyzed Enantioselective Alkylation of Pyrrole with β,γ-Unsaturated α-Ketoesters: Application to One-Pot Construction of the Seven-Membered Ring by Merging a Gold Catalysis

A highly enantioselective Friedel-Crafts alkylation of pyrrole to β,γ-unsaturated α-ketoesters was developed by virtue of a chiral copper complex, affording the alkylated derivatives of pyrrole with good yields and excellent enantioselectivities. Moreover, merging copper catalysis with gold catalysis realized a one-pot construction of the seven-membered ring to give annulated pyrroles with moderate to good yields and high enantiomeric excesses.

Copper-catalyzed condensation of imines and α-diazo-β-dicarbonyl compounds: modular and regiocontrolled synthesis of multisubstituted pyrroles

The Cu-catalyzed condensation of ketimines and diazodicarbonyl compounds enables the rapid and regiocontrolled synthesis of pharmaceutically relevant multisubstituted pyrroles.

In the presence of a copper(ii) catalyst, enolizable imines bearing various N-substituents and α-diazo-β-ketoesters undergo denitrogenative and dehydrative condensation to afford highly substituted pyrroles in moderate to good yields with exclusive regioselectivity. The reaction likely involves nucleophilic addition of the imine nitrogen to a copper carbenoid, tautomerization of the resulting azomethine ylide to an α-enaminoketone, and a subsequent enamine–ketone cyclocondensation. With Yb(OTf)₃ as a unique cocatalyst, α-diazo-β-diketones also participate in the same condensation reaction. The present reaction is applicable to acyclic, exocyclic, and endocyclic imines with tolerance of a broad range of functional groups and heterocyclic moieties, thus opening a new convenient route for the synthesis of the lamellarin family of natural products.

Enantioselective Synthesis of Pyrrole-Based Spiro- and Polycyclic Derivatives by Iridium-Catalyzed Asymmetric Allylic Dearomatization and Controllable Migration Reactions

The first highly diastereo- and enantioselective synthesis of five-membered spiro-2H-pyrroles was achieved using an Ir-catalyzed asymmetric allylic dearomatization reaction. The spiro-2H-pyrrole derivatives readily undergo a controllable and stereospecific allylic migration under acid catalysis, providing polycyclic pyrrole derivatives in excellent yields and ee values. Additionally, the novel Ir-complex K1, derived from [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) and N-benzhydryl-N-phenyldinaphthophosphoramidite (BHPphos), showed excellent control of both diastereo- and enantioselectivities.