Reversed Allylation of 3-Alkenyl Indoles Using Allyl Boronic Acids: Access to Tryptamine Based Alkaloids.

All-carbon quaternary and tertiary stereocenters connected at the C2-position of functionalizable C3-alkylated indole nucleus are commonly occurring frameworks found in many indole alkaloids of medicinal importance. Their direct access is scarcely reported, a long-standing problem, and developing a unique yet simple method can pave the pathway to an entirely different retrosynthetic route for the total synthesis of these alkaloids. Herein, this problem is addressed by developing an unprecedented branch-selective allylation strategy employing a broad range of structurally and electronically different 3-alkenyl-indoles and allylboronic acids.

Total Synthesis and Stereochemical Assignment of Enteropeptin A.

The total synthesis and structural elucidation of the antimicrobial sactipeptide enteropeptin A is reported. Enteropeptin A contains a thioaminoketal group with an unassigned stereochemical configuration that is embedded in a highly unusual thiomorpholine ring. In this synthesis, a linear peptide containing a dehydroamino acid and a pendant cysteine residue is subjected to Markovnikov hydrothiolation by a dithiophosphoric acid catalyst.

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.

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.

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.

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.

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.

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.

Brønsted Acid Catalyzed One-Pot Benzannulation of 2-Alkenylindoles under Aerial Oxidation: A Route to Carbazoles and Indolo[2,3- a]carbazole Alkaloids.

A one-pot, protecting-group-free benzannulation of 2-alkenylindoles with readily available 1,3-dicarbonyls is demonstrated to construct structurally diverse carbazoles. The use of a cheap Brønsted acid catalyst and air as the sole oxidant exemplifies the economic viability of this protocol. The execution of four different reactions successively to generate the medicinally important indolocarbazole core is also achieved.