Rh(2)(II)-catalyzed synthesis of carbazoles from biaryl azides

KOtBu mediated efficient approach for the synthesis of fused heterocycles via intramolecular O-/N-arylations

KO^tBu mediated an efficient methodology has been developed for the synthesis of 6H-benzo[c]chromenes, 6H-benzo[c]chromen-6-ones, carbazoles, dibenzofurans and dibenzooxepins.

Theoretical studies of iron(III)-catalyzed intramolecular C-H amination of azides

Density functional theory calculations have been carried out to study the reaction mechanism of the [Fe(III)(F20TPP)Cl] catalyzed C-H amination reaction. The calculations show that the classical three-step mechanism for other metals (Ru, Rh, Ir and Zn), including N2 liberation, C-N bond formation and 1,2-hydrogen shift, does not fit the iron(III)-catalyzed system. After N2 liberation, the favorable reaction pathway for the iron(iii)-catalyzed system is a 1,2-hydrogen shift preceding C-N bond formation, i.e., a H-abstraction/radical rebound mechanism.

Development of a Suzuki cross-coupling reaction between 2-azidoarylboronic pinacolate esters and vinyl triflates to enable the synthesis of [2,3]-fused indole heterocycles

The scope and limitations of a Suzuki reaction between 2-azidoarylboronic acid pinacolate esters and vinyl triflates are reported. This cross-coupling reaction enables the regioselective synthesis of indoles after a subsequent Rh(II)2-catalyzed sp(2)-C-H bond amination reaction.

Transition-metal-free direct arylation: synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls and mechanism by DFT calculations

A transition-metal-free, regioselective direct aryl-aryl bond-forming process for the synthesis of halogenated 2-amino-2'-hydroxy-1,1'-biaryls that are currently either inaccessible or challenging to prepare using conventional methods is disclosed. The addition of ArMgX to an o-halonitrobenzene at low temperature generates a transient N,O-biarylhydroxylamine that rapidly undergoes either [3,3]- or [5,5]-sigmatropic rearrangement in one-pot to form a 2-amino-2'-hydroxy-1,1'-biaryl or 1-amino-1'-hydroxy-4,4'-biaryl, respectively. The periselectivity is controlled by the choice of solvent and temperature. This direct arylation process is also readily scalable (1-10 mmol). DFT calculations suggest that from the N,O-biarylhydroxylamine intermediate there is a low-energy stepwise pathway that involves initial Mg-mediated N-O bond cleavage followed by pathway branching toward either [3,3]- or [5,5]-rearrangement products via C-C bond formation and rearomatization.

Dibenzo[1,2,5]thiadiazepines are non-competitive GABAA receptor antagonists

A new process for obtaining dibenzo[c,f][1,2,5]thiadiazepines (DBTDs) and their effects on GABA(A) receptors of guinea pig myenteric neurons are described. Synthesis of DBTD derivatives began with two commercial aromatic compounds. An azide group was obtained after two sequential reactions, and the central ring was closed via a nitrene to obtain the tricyclic sulfonamides (DBTDs). Whole-cell recordings showed that DBTDs application did not affect the holding current but inhibited the currents induced by GABA (I(GABA)), which are mediated by GABA(A) receptors. These DBTDs effects reached their maximum 3 min after application and were: (i) reversible, (ii) concentration-dependent (with a rank order of potency of 2c = 2d > 2b), (iii) mediated by a non-competitive antagonism, and (iv) only observed when applied extracellularly. Picrotoxin (which binds in the channel mouth) and DBTDs effects were not modified when both substances were simultaneous applied. Our results indicate that DBTD acted on the extracellular domain of GABA(A) channels but independent of the picrotoxin, benzodiazepine, and GABA binding sites. DBTDs used here could be the initial model for synthesizing new GABA(A) receptor inhibitors with a potential to be used as antidotes for positive modulators of these receptors or to induce experimental epilepsy.

Photochemistry with laser radiation in condensed phase using miniaturized photoreactors

Miniaturized microreactors enable photochemistry with laser irradiation in flow mode to convert azidobiphenyl into carbazole with high efficiency.

Ruthenium porphyrins-catalyzed atom-efficient amination of C-H bonds by arylazides

Benzylic amines are synthesized in yield up to 90% by the Ru(TPP)CO -catalyzed amination of both exocyclic and endocyclic benzylic C-H bonds. The choice of arylazides as nitrogen sources confers to the methodology a good sustainability due to the formation of molecular nitrogen as the only stoichiometric by-product. A preliminary mechanistic investigation evidenced a critical role of the hydrocarbon concentration to drive the chemoselectivity of the reaction.

Ruthenium-catalyzed γ-carbolinium ion formation from aryl azides; synthesis of dimebolin

A range of γ-carbolines were produced stereoselectively from ruthenium(III)-catalyzed reactions of 3-pyridyl substituted aryl azides. Other catalysts and conditions were neither as selective nor as high-yielding. This method was used to synthesize dimebolin in a concise and efficient manner.