A One-Pot Assembly of Fully Substituted Alkyl 5‑Aminothiophene-2-carboxylates from Allenes, Isothiocyanates, and Alkyl 2‑Bromoacetates

A novel simple approach to highly functionalized multisubstituted thiophenes such as alkyl 4-alkoxy-5-amino-3-methylthiophene-2-carboxylates through the one-pot sequential reaction of α-lithiated alkoxyallenes with isothiocyanates and alkyl 2-bromoacetates has been discovered. The process proceeds quickly (30–45 min) via in situ formation and intramolecular cyclization of alkyl 2-[(2-alkoxybuta-2,3-dienimidoyl)­sulfanyl]­acetates (1-aza-1,3,4-trienes)

Transition-Metal-Free C‑Vinylation of Ketones with Acetylenes: A Quantum-Chemical Rationalization of Similarities and Differences in Catalysis by Superbases MOH/DMSO and <i>t</i>BuOM/DMSO (M = Na, K)

Transition-metal-free C-vinylation of acetone with phenylacetylene catalyzed by superbases MOH/DMSO and <i>t</i>BuOM/DMSO (M = Na, K) has been theoretically evaluated in the B3LYP/6-311++G**//B3LYP/6-31+G* approach to rationalize similarities and differences in activity of the above catalytic systems. The close solvate surroundings of sodium and potassium <i>tert-</i>butoxides have been studied. Formation of <i>t</i>BuOM·<i>n</i>DMSO complexes and their structure and thermodynamic stability are discussed in comparison with similar complexes of alkali-metal hydroxides MOH·<i>n</i>DMSO. Activation barriers of the title reaction in the presence of <i>t</i>BuOM·<i>n</i>DMSO complexes are found to be less than those with MOH·<i>n</i>DMSO complexes participating

Decorated Cyclopentadienes from Acetylene and Ketones in Just Two Steps

The products of the one-pot assembly of acetylene and ketones in the KOH/DMSO system, 7-methylene-6,8-dioxa­bicyclo­[3.2.1]­octanes, undergo an acid-catalyzed (CF₃COOH, room temperature) rearrangement to rarely substituted cyclopenta­dienes in good-to-excellent yields. The mechanism of the rearrangement has been supported by the isolation and corresponding transformations of two intermediates

A One-Pot Synthesis of 2‑Aminopyrimidines from Ketones, Arylacetylenes, and Guanidine

The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBu^<i>t</i>/DMSO system leads to 2-aminopyrimidines in up to 80% yield. Depending on structure of the starting ketones, the aromatization of intermediate dihydropyrimidines occurs either with loss of hydrogen molecules or methylbenzenes. The latter process takes place in the ketones, in which one of the substituents is not a methyl group. The reaction conditions are tolerable for dialkyl-, aryl­(hetaryl) alkyl-, and cycloalkyl ketones

Transition-Metal-Free, Atom- and Step-Economic Synthesis of Aminoketopyrrolizines from Benzylamine, Acylethynylpyrroles, and Acylacetylenes

A concise, atom-economic strategy for the synthesis of pyrrolizines with amino and keto substituents has been developed. It includes the following key steps: (i) the base-catalyzed (K₃PO₄/DMSO) addition of a benzylamine to 2-acylethynylpyrroles and (ii) noncatalyzed addition of enaminones obtained to the triple bond of acylacetylenes followed by intramolecular cyclization of the intermediate pentadiendiones thus formed to the target 1-(benzylamino)-2-acyl-3-methylenoacylpyrrolizines

Transition-Metal-Free Superbase-Promoted Stereoselective α‑Vinylation of Ketones with Arylacetylenes: A General Strategy for Synthesis of β,γ-Unsaturated Ketones

A wide variety of β,γ-unsaturated ketones of <i>E</i> configuration have been obtained in good to excellent yields via KO^<i>t</i>Bu/DMSO promoted α-vinylation of aliphatic, cycloaliphatic, and alkyl aromatic (heteroaromatic) ketones with diverse arylacetylenes

Transition-Metal Free Mechanochemical Approach to Polyyne Substituted Pyrroles

In this contribution, the synthesis of long chain hexatriynyl- and octatetraynyl-substituted pyrroles in one step from 1-halopolyyne precursors is reported. The products were obtained via a mechanochemical approach by simple grinding of 1-haloalkynes with <i>N</i>-substituted pyrroles and potassium carbonate which played a role of heterogeneous catalyst and this solvent- and transition metal-free approach is unprecedent in the synthesis of new, organic, long chain polyynes. Additionally, an extensive X-ray single crystal study of pyrrole end-capped polyynes is presented. Such compounds are possible substrates for different oligoheterocycles and have a significant application potential such as for instance molecular wires

Transition-Metal Free Mechanochemical Approach to Polyyne Substituted Pyrroles

In this contribution, the synthesis of long chain hexatriynyl- and octatetraynyl-substituted pyrroles in one step from 1-halopolyyne precursors is reported. The products were obtained via a mechanochemical approach by simple grinding of 1-haloalkynes with <i>N</i>-substituted pyrroles and potassium carbonate which played a role of heterogeneous catalyst and this solvent- and transition metal-free approach is unprecedent in the synthesis of new, organic, long chain polyynes. Additionally, an extensive X-ray single crystal study of pyrrole end-capped polyynes is presented. Such compounds are possible substrates for different oligoheterocycles and have a significant application potential such as for instance molecular wires

Exploring Acetylene Chemistry: A Transition Metal-Free Route to Dienyl 6,8-Dioxabicyclo[3.2.1]octanes from Ketones and Acetylenes

Dienyl derivatives of 6,8-dioxabicyclo[3.2.1]­octanes, closely related to naturally abundant molecules, have been synthesized from 2-acetyl-3,4-dihydropyrans (readily available from ketones and acetylene in two steps), which further add to aryl­(hetaryl)­acetylenes in the KOBu^t/DMSO superbase system (105 °C, 1.5 h) to stereoselectively give the corresponding <i>E</i>-styryl adducts. The latter undergo ring closure (NH₄Cl/H₂O, acetonitrile, reflux, 8 h) to form the 6,8-dioxabicyclo[3.2.1]­octane core decorated with the (1<i>Z</i>,3<i>E</i>)-diene substituent

An Expedient Access into Functionalized Furan/3(2<i>H</i>)-furanone Ensembles via Microwave-Assisted Domino Reactions

<div><p></p><p>A one-pot linkage between furan and 3(2H)-furanone rings has been effected via the microwave-assisted Et₃N-catalyzed domino condensation of the furan and benzofuran carboxylic acids with available cyanopropargylic alcohols (MeCN, 100 °C, 1.2 atm, 2-17 h). Despite involving a number of C-H-forming/breaking steps, the assembly is chemoselective and the final products, 5-(2-furyl)-3(2H)-furanones, are formed in 59-96% yields.</p></div