A toolbox approach to revealing a series of naphthocarbazoles to showcase photocatalytic reductive syntheses.

The development of highly reducing photocatalysts to functionalize arenes the generation of reactive aryl radicals under mild and environmentally benign reaction conditions has emerged as a noteworthy approach in the realm of organic synthesis. Herein, we report a readily synthesized series of novel naphthocarbazole derivatives (NCs) as organo-photocatalysts, which, upon irradiation under 390 nm light, acquire high reducing power to catalyze several reductive transformations. The promising properties revealed by in depth photophysical and electrochemical studies ( = -1.

Direct Asymmetric Synthesis of α-Aminoimines from 1,2-Bis-N-Sulfinylimines by Using Allyl Boronic Acids.

A unique direct asymmetric synthesis of α-aminoimines is realized, through rapid and exclusive mono-allylation of chiral bis-N-sulfinylimines using allylboronic acids. The highly selective allylation was possible as electrophilic imine functional group in the product α-aminoimines remained unreactive towards allyl boronic acid nucleophiles. Notably, by varying the geometry and chiral auxiliary, all four isomers of the α-aminoimines were accessed from readily available precursors.

Asymmetric 1,2-Migration at Vicinal Tetrasubstituted Stereocenters Constructed from α-Keto Imines.

A carbonyl-assisted asymmetric 1,2-migratory allylation through in situ generation of vicinal tetrasubstituted stereocenters is reported to access enantiopure α-amino ketones and amino alcohols with excellent yields and diastereoselectivities. In a remarkable divergence, despite higher steric hindrance, the allylation exclusively occurs on ketones over imines in the first step, followed by a face-selective 1,2-allyl transfer, thus highlighting an exciting interplay between two distinct electrophiles. The methodology distinguishes itself through its adaptability to gram-scale synthesis, showcasing broad functional-group tolerance and stereodivergence.

Carbazoquinocin Analogues as Small Molecule Biomimetic Organocatalysts in Dehydrogenative Coupling of Amines.

A new series of carbazole-cored biomimetic -quinone catalysts structurally resembling carbazoquinocin alkaloids have been introduced to promote tunable, metal cocatalyst-free, organocatalytic, dehydrogenative amine oxidation under aerobic conditions. Differently substituted benzyl amines were tolerated under optimized conditions to provide imines in excellent yields. Further efficacy of the catalyst was demonstrated by synthesizing cross-coupled imines efficiently.

Solution-Phase Late-Stage Chemoselective Photocatalytic Removal of Sulfonyl and Phenacyl Groups in Peptides.

Herein, BPC catalyzed visible-light-triggered target-specific late-stage solution phase desulfonylation from tryptophan in oligopeptides is portrayed by overcoming the isolation issue up to octamers. This robust and mild method is highly predictable and chemoselective, tolerating myriad of functional groups in aza-heteroaromatics and peptides. Interestingly, reductive desulfonylation is also amenable to biologically significant reactive histidine and tyrosine side chains, signifying the versatility of the strategy.

Construction of C2-indolyl-quaternary centers by branch-selective allylation: enabling concise total synthesis of the (±)-mersicarpine alkaloid.

Herein we report a branch-selective allylation strategy for accessing C2-indolyl-all-carbon quaternary centers using allylboronic acids. This approach boasts broad functional group tolerance, scalability, and relies on easily accessible allyl alcohol precursors. Importantly, the C3-position of the indole remains free, offering a handle for further synthetic refinement.

Annulative π-Extension by Cp*Co(III)-Catalyzed Ketone-Directed -Annulation: An Approach to Access Fused Arenes.

A masked-bay-region selective first-row transition-metal Cp*Co(III)-catalyzed annulative π-extension of arene-derived ketones is achieved to afford K-region-functionalized benzo[]pyrenes, benzotetraphenes, and pyrenes. Comprehensive density functional theory studies buttress the mechanistic pathway comprising key steps like -C-H activation, alkyne 1,2-migratory insertion, and nucleophilic attack toward ketone, this attack being the rate-determining step. In addition, π-conjugated 1,1'-bipyrenes, potential photocatalyst pyrene-quinones, and putative n-type semiconductor cyano group-containing dibenzo[,]tetracenes are also accessed.

Late-Stage Halogenation of Peptides, Drugs and (Hetero)aromatic Compounds with a Nucleophilic Hydrazide Catalyst.

Unlike its other halogen atom siblings, chlorination of a bioactive compound can change its physiological characteristics, improve its pharmacological profile, and function as a point of diversification through cross-coupling reactions. As a result, it has been a crucial strategy for drug discovery and development. However, functional groups such as amines, amides, hydroxy groups, or carboxylic acids trap the Cl , severely limiting the reactivity and making direct chlorination far too difficult to be practical.

Annulative π-Extension by Rhodium(III)-Catalyzed Ketone-Directed C-H Activation: Rapid Access to Pyrenes and Related Polycyclic Aromatic Hydrocarbons (PAHs).

Annulative π-extension (APEX) reaction has become a powerful tool for the precise synthesis of well-defined polycyclic aromatic hydrocarbons (PAHs) such as nanographene, graphene, and other PAHs possessing unique structure. Herein, an APEX reaction has been realized at the masked bay-region for the efficient and rapid synthesis of valuable PAH, pyrene, bearing substitutions at the most challenging K-region. Rh -catalyzed ketone-directed C-H activation at the peri-position of a naphthyl-derived ketone, alkyne-insertion, intramolecular nucleophilic attack at the carbonyl-group, dehydration, and aromatization steps occurred in one-pot to effectuate the protocol.

Development of Carbazole-Cored Organo-Photocatalyst for Visible Light-Driven Reductive Pinacol/Imino-Pinacol Coupling.

Benzoperylenocarbazole (BPC), a unique carbazole-based organophotocatalyst, is reported herein as a potent organo-photoreductant. Lower excited state oxidation potential (-2.0 V vs SCE) and reasonable excited state lifetime (4.

Cp*Co(III)-catalyzed thiocarbamate-directed C-H aminocarbonylation, amination, and cascade annulation of pyrroles.

Cobalt(III)-catalyzed thiocarbamate directed aminocarbonylation and amination of C-H bonds are described to access diverse amides. Biologically relevant pyrrolo[1,2-]imidazoles were readily accessed one-pot intramolecular cyclization at the thiocarbamoyl directing group. Notably, C-N amidation proceeded smoothly with an elusive catalyst TON of 250 for this Cp*Co(III)-catalysis.

Synthesis of functionalized indoles cascade benzannulation strategies: a decade's overview.

Indoles are one of the most prominent aromatic heterocycles in the organic chemistry field. Due to their widespread presence in various natural products, alkaloids, drugs, approved medicines, . the synthesis and functionalization of indoles are of great interest.

An expeditious route to sterically encumbered nonproteinogenic α-amino acid precursors using allylboronic acids.

A diastereoselective allylation of -butane sulfinyl α-iminoesters using allylboronic acids is developed to obtain optically active non-proteinogenic α-amino acid precursors in good yields and diastereoselectivities. Gram-scale synthesis, broad tolerance of functional groups, excellent stereodivergence, post-synthetic modifications, and easy removal of the chiral auxiliary are some of the key highlights. The protocol is applicable to various amino acids and short peptides, resulting in the incorporation of these precursors at the N-terminal position.

Cascade Benzannulation Approach for the Syntheses of Lipocarbazoles, Carbazomycins, and Related Alkaloids.

Herein, a state-of-the-art one-pot cascade benzannulation technique for the efficacious synthesis of valuable 3-hydroxy-2-methyl carbazoles, a linchpin of more than 25 carbazole-based alkaloids, is unveiled from readily affordable fundamental commodities. The key step of this strategy is gaining aromaticity by site-selective elimination of hydroxyl group controlled by nucleophilicity of the indole ring. The present strategy shows excellent functional group tolerance with a broad substrate scope.

Cascade annulative π-extension for the rapid construction of carbazole based polyaromatic hydrocarbons.

A Brønsted acid catalyzed cascade benzannulation strategy for the one-pot synthesis of densely populated poly-aryl benzo[a]carbazole architectures is disclosed from easily affordable fundamental commodities. The efficacy of this technique was further validated via the concise synthesis of structurally unique carbazole based poly-aromatic hydrocarbons. Furthermore, the photo-physical properties of the synthesized compounds are thoroughly investigated.

A one-pot "back-to-front" approach for the synthesis of benzene ring substituted indoles using allylboronic acids.

Synthesis of only benzene ring functionalized indoles and poly-substituted carbazoles is reported via a one-pot triple cascade benzannulation protocol. Usage of differently substituted and readily accessible allylboronic acids as a 3-carbon annulating partner enables diverse aliphatic and aromatic substitution patterns, which is still a daunting task. This scalable synthetic protocol tolerates broad scope, thus enabling further downstream modifications.

Cooperativity within the catalyst: alkoxyamide as a catalyst for bromocyclization and bromination of (hetero)aromatics.

Alkoxyamide has been reported as a catalyst for the activation of N-bromosuccinimide to perform bromocyclization and bromination of a wide range of substrates in a lipophilic solvent, where adequate suppression of the background reactions was observed. The key feature of the active site is the alkoxy group attached to the sulfonamide moiety, which facilitates the acceptance as well as the delivery of bromonium species from the bromine source to the substrates.

Carbamates: A Directing Group for Selective C-H Amidation and Alkylation under Cp*Co(III) Catalysis.

The selective reactivity of carbamate and thiocarbamate toward alkylation and amidation is reported under stable, high-valent, cost-effective cobalt(III) catalysis. This method reveals the wide possibility of designing a different branch of synthetically challenging yet highly promising asymmetric catalysts based on BINOL and SPINOL scaffolds. Late-stage C-H functionalization of l-tyrosine and estrone was also achieved through this approach.

One-pot access to tetrahydrobenzo[c]carbazoles from simple ketones by using O as an oxidant.

An effective and operationally simple one-pot Brønsted acid catalyzed cascade method is demonstrated for the synthesis of diversely functionalized carbazole frameworks starting from protecting group free 2-alkenyl indoles. The employment of easily available unactivated ketones as annulating partners, mostly unexplored for the synthesis of carbazoles, is the major highlight of this protocol. This protocol is step- and atom-economical, uses molecular oxygen as the green oxidant, and gives water as the only by-product and is amenable to different functional groups.

Brønsted Acid-Catalyzed Tandem Pinacol-Type Rearrangement for the Synthesis of α-(3-Indolyl) Ketones by Using α-Hydroxy Aldehydes.

A Brønsted acid-catalyzed pinacol-type rearrangement pathway is reported here to synthesize various substituted α-(3-indolyl) ketones by employing unprotected indoles and α-hydroxy aldehydes as coupling partners. Utilization of economic and readily available Brønsted acid catalyst and use of simple starting precursors exemplify the economic viability of this method. Under this developed protocol, selective migration of aryl over alkyl or a second aryl group is observed depending upon the migratory aptitude of the substituents.

A Brønsted Acid Catalyzed Cascade Reaction for the Conversion of Indoles to α-(3-Indolyl) Ketones by Using 2-Benzyloxy Aldehydes.

A Brønsted acid catalyzed, operationally simple, scalable route to several functionalized α-(3-indolyl) ketones has been developed and the long-standing regioisomeric issue has been eliminated by choosing appropriate carbonyls. A readily available and cheap bottle reagent was used as the catalyst. This protocol was also applicable to the synthesis of densely functionalized α-(3-pyrrolyl) ketones.

On-Water Cp*Ir(III)-Catalyzed C-H Functionalization for the Synthesis of Chromones through Annulation of Salicylaldehydes with Diazo-Ketones.

A high-valent Ir(III)-catalyzed C-H bond functionalization is carried out for the first time on water for the synthesis of a biologically relevant chromone moiety. The C-H activation and annulation of salicylaldehydes with diazo-compounds provided the desired chromones. The synthesis of C3-substitution-free chromones has also been demonstrated by a one-pot decarboxylation by employing tert-butyl diazoester.

Harnessing Stereospecific Z-Enamides through Silver-Free Cp*Rh(III) Catalysis by Using Isoxazoles as Masked Electrophiles.

The stereospecific synthesis of Z-enamides is described in this paper. For the first time, isoxazoles have been employed as electrophiles in C-H functionalization to afford thermodynamically less stable Z-enamides utilizing salicylaldehydes in an atom- and step-economic fashion. The stereochemistry of enamides might originate from the relative disposition of atoms present in isoxazole and the intramolecular hydrogen bonding.

Formal [4 + 2] benzannulation of 2-alkenyl indoles with aldehydes: a route to structurally diverse carbazoles and bis-carbazoles.

Construction of structurally diverse carbazoles and bis-carbazoles by protecting-group-free formal [4 + 2]-benzannulation of 2-alkenyl indoles and aldehydes is demonstrated. The sequence of four different reactions is executed in one-pot using readily available and cheap bottle reagents as catalysts rendering this method attractive. The incorporation of inexpensive and environmentally benign molecular oxygen as the oxidant into the final aromatization step enables tolerance of several functional groups.