N,N-Dimethylformamide: much more than a solvent

A new method for the efficient, practical, and highly regioselective direct palladium-catalyzed C-3 arylation of free (NH)-indole and its electron-rich 1-unsubstituted derivatives under ligandless conditions is described. The reactions, which are run outside a glovebox without purification of solvent and reagents, involve treatment of free (NH)-indoles with activated, unactivated, and deactivated aryl bromides in refluxing toluene in the presence of K2CO3 as the base and a catalyst system consisting of a combination of Pd(OAc)2 and benzyl(tributyl)ammonium chloride. The experimental results are consistent with a catalytic cycle based on an electrophilic palladation pathway at the 3-position of 1-indolyl potassium salts.

Direct palladium-catalyzed C-3 arylation of free (NH)-indoles with aryl bromides under ligandless conditions.

This brief account describes our progress on the regioselective synthesis of medium-sized heterocycles. Formation of the medium-ring (seven-, eight-, nine-membered) oxa-, aza-, thia, oxa-thia- and aza-thia-heterocycles has been achieved by the intramolecular metal-mediated cyclization (especially Pd-catalyzed), diene and enyne metathesis, thiol-mediated cyclization, iodocyclization and azide-alkyne cycloaddition.

Regioselective formation of medium-ring heterocycles of biological relevance by intramolecular cyclization

This brief review represents the synthesis of heterocyclic compounds via application of Heck reaction in recent years.

Recent advances in the application of the heck reaction in the synthesis of heterocyclic compounds

A convenient synthesis of pyrrolopyridines and 2-substituted indoles by gold-catalyzed cycloisomerization

New Heck coupling strategies for the arylation of secondary and tertiary amides via palladium-catalyzed intramolecular cyclization

A new synthetic protocol has been developed by the implementationof the palladium-mediated benzylic C-H activation followedby tethered intramolecular arylation strategy to give linearly fusedand unusually oxidized pyridocoumarin derivatives.

Palladium-Catalyzed TetheredIntramolecular Arylation: An Unusual Synthesis of LinearlyFused Pyridocoumarin Derivatives

A number of 2-(prop-2-ynylthio)-1H-indoles have been utilized tor the synthesis of 3-benzylthiazolo[3,2-a]indoles by Sonogashira acetylide-coupling followed by triethylamine-induced regioselective cyclization in a one-pot operation. The cyclization is dependent on the nature of the substituents on the phenyl ring of the substrates.

One-Pot Regioselective Synthesisof 3-Benzylthiazolo[3,2-a]indolesby Sequential Sonogashira Coupling Followed by Triethylamine-Induced Cyclization

Two homologous series of highly anisotropic diimines containing five and six aromatic rings in the mesogenic core derived from 1,4-terephthaldehyde and 4-formylphenyl-4-formylbenzoate have been synthesized and characterized by spectroscopic methods. The liquid-crystalline phases and the phase-transition temperatures are investigated using a polarizing microscope attached to a hot stage and differential scanning calorimetry. Most of the compounds are thermally stable and exhibit smectic and nematic phases over a large thermal range. In the majority of the compounds studied, a SmC phase exists over a very broad temperature range. The importance of the alkyl chain length in competing with the size of the aromatic core in determining the phase variant and in the increase of thermal range of the mesomorphism in a homologous series is described.

Sanjay Nath

Papers

New Heck coupling strategies for the arylation of secondary and tertiary amides via palladium-catalyzed intramolecular cyclization

Palladium-Catalyzed TetheredIntramolecular Arylation: An Unusual Synthesis of LinearlyFused Pyridocoumarin Derivatives

One-Pot Regioselective Synthesisof 3-Benzylthiazolo[3,2-a]indolesby Sequential Sonogashira Coupling Followed by Triethylamine-Induced Cyclization

Synthesis, Characterization, and Mesogenic Properties of Anisotropic Imines

Regioselective Synthesis of Benzofuran‐Annulated Six‐Membered Sulfur Heterocycles by Aryl Radical Cyclization