Intramolecular Fischer Indole Synthesis in Combination with Alkyne Hydroarylation: Synthesis of Tetracyclic Chromeno-indoles

Copper-Catalyzed Cross-Coupling Between (E)-1,2-Diiodoethene and Carbazates: Entry to β-Functionalized N-Alkenylcarbazates

Aims:

This work aims to widen the scope of methodologies to prepare functionalized N-alkenylcarbazates.

Background:

Alkenylcarbazates are generally prepared via Aza-Baylis-Hillman reactions, nucleophilic attack on ketones or a tandem carbometallation/amidation reaction of alkynes.

Objective:

The objective of this work is to develop a method to prepare functionalized Nalkenylcarbazates that alleviates the problem encountered in the above methods (use of electron deficient alkenes, use of stoiechiometric amounts of metal, access to symmetrical dicarbazates only).

Methods:

Use of copper-catalyzed cross-coupling between vinylic diiodide and carbazates to prepare functionalized N-alkenylcarbazates.

Results:

Various β-iodovinylcarbazates were synthesized with up to good yields. The highest yields were obtained using dicarbazates. Functionalization of β-iodovinylcarbazate demonstrated that the vinyl iodide moiety of these molecules can be substituted by a variety of functional groups via transition metal-catalyzed coupling reactions.

Conclusion:

Copper-catalyzed cross-coupling reaction is efficient to prepare functionalized N-alkenylcarbazates.

Asymmetric Divergent Total Syntheses of (+)-Decursivine and (+)- Serotobenine via Intramolecular Fischer Indole Synthesis

A new asymmetric synthetic route to (+)-decursivine and (+)-serotobenine is formulated. The key developments are the de novo construction of the crucial eight-membered 3,4-fused tricyclic indole ring engaged by the intramolecular Fischer indole synthesis and the stereocontrolled assembly of the dihydrobenzofuran subunit mediated by the asymmetric intramolecular Rh-carbenoid C-H insertion. BF₃-mediated selective C15 epimerization followed by removal of the amine masking groups completed the target natural compounds' asymmetric and divergent total syntheses.

Synthesis of 3,4-Fused Tricyclic Indoles through Cascade Carbopalladation and C-H Amination: Development and Total Synthesis of Rucaparib

3,4-Fused tricyclic indole scaffolds are ubiquitous in bioactive natural products and pharmaceuticals. A new protocol for the synthesis of 3,4-fused tricyclic indoles has been developed through cascade carbopalladation and C-H amination with N,N-di-tert-butyldiaziridinone. The protocol allows access to a range of 3,4-fused tricyclic indoles, including those containing various linkers and fused with medium-sized rings. Rucaparib can be synthesized via this reaction, providing an advantageous synthetic method for the FDA-approved cancer medicine.

New Synthetic Routes to (+)-Uleine and (-)-Tubifolidine: General Approach to 2-Azabicyclo[3.3.1]nonane Indole Alkaloids

Novel asymmetric synthetic routes to (+)-uleine and (-)-tubifolidine are reported herein. The regioselective formation of enol triflates from 2-azabicyclo[3.3.1]nonane ketones followed by indolizations of the resultant ene-hydrazides allowed the efficient construction of key indole intermediates, facilitating the total synthesis of the target natural alkaloids.

Synthesis of 4,7-Difunctionalized Indoles via Imino Exchange and Sulfinyl Migration

A process that rapidly assembles 4,7-difunctionalized indoles from 2-alkynycyclohexadienimines, sulfinamides, and nucleophiles (amines or alcohols) was developed. The process involves imino exchange, cascade cyclization/1,4-nucleophilic addition/aromatization, and 1,3-migration of the sulfinyl group. The 7-sulfinyl group is easy to convert into the sulfonyl or the thioether group through a simple oxidation and reduction reaction.

One pot synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles via tandem C–H olefination/aza-Michael addition

An unprecedented one-pot C–H olefination/aza-Michael addition tandem process has been developed for the synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles and alkenes using a [Cp*RhCl₂]₂/AgOAc/Me₄NOAc catalytic system.

Lewis Acid Catalyzed Regioselective Hydroheteroarylation of Pentafulvenes

A diverse approach toward the catalytic regioselective nucleophilic addition of nitrogen heterocycles to Lewis acid activated pentafulvenes has been established. The developed protocol introduces pentafulvenes as nonsymmetrical alkenes for the hydroheteroarylation reaction, providing alkylidenecyclopentenylation at the C-3 position of indoles and the C-2 position of pyrrole.

Microwave assisted synthesis, characterization and biocidal activities of some new chelates of carbazole derived Schiff bases of cadmium and tin metals

This study is planned to report the advancement of green microwave approach in the fabrication of a new series of biologically potent (N^X, where X=O/S) donor Schiff bases and their cadmium(II) and tin(II) complexes. The ligands and their metal complexes have been characterized in terms of elemental analysis, molar ionic conductance, magnetic moment and spectral (IR, UV-Vis, NMR ((1)H, (119)Sn), FAB-mass, thermal and XRD) data. The data revealed that the ligands coordinated to the metal center via nitrogen and oxygen/sulfur atoms and form an octahedral arrangement of the ligands around central metal atom. All compounds were evaluated for their in vitro antimicrobial activities against two pathogenic bacteria Bacillus subtilis and Escherichia coli and two fungi Aspergillus niger and Aspergillus flavus by standard disc diffusion method. The discs were stored in an incubator at 37°C. The compounds were dissolved in DMF at 500 and 1000 ppm concentrations for screening biocidal activity. The compounds were dissolved in DMF to get the 100 and 200 ppm concentration of test solutions for screening fungicidal activity. The inhibition zone around each disc was measured (in mm) after 24 h and 96 h for biocidal and fungicidal activities respectively.

Rhodium-catalyzed intramolecular annulation via C–H activation leading to fused tricyclic indole scaffolds

A new method for the synthesis of fused tricyclic indoles via a rhodium catalyzed intramolecular C–H activation reaction is described.

Rhodium(iii)-catalyzed intramolecular amidoarylation and hydroarylation of alkyne via C–H activation: switchable synthesis of 3,4-fused tricyclic indoles and chromans

An intramolecular amidoarylation and hydroarylation of alkyne via rhodium(iii)-catalyzed C–H activation was developed for the switchable synthesis of 3,4-fused indoles and chromans.