RESUMEN
We have discovered that three molecules of arylacetylene are rapidly (15 min) assembled with one molecule of nitrile at room temperature in the KOBut/DMSO system to afford 2-aryl-3-arylethynyl-4-aryl-5-benzyl-1H-pyrroles in up to 76% yield. We assume that this unprecedented self-organization process involves the cascade addition of acetylenic carbanions, first to the CîN, then to the CîC and CîC bonds of the intermediates, followed by pyrrole ring closure via the intramolecular nucleophilic addition of the NH functional group to the CîC bond of the final intermediates.
RESUMEN
Pure (E)-alkenoyl dihydropyrans are stereoselectively assembled from 2-acetyl-3,4-dihydropyrans (products of one-pot self-organization of acetylene gas and ketones) and aromatic aldehydes (52-86% yields). Furthermore, (E)-alkenoyl dihydropyrans undergo ring opening (acid hydrolysis) to afford 5-hydroxy-1,6-diketones (44-67% yields) and acetyl-2-(E)-styryl-2,3-dihydroxycyclopentanes (19-32% yields), both as single diastereomers.
Asunto(s)
Acetileno , Cetonas , Ciclopentanos , Estructura Molecular , EstereoisomerismoRESUMEN
Unique bridgehead nitrones, 8-oxa-6-azabicyclo[3.2.1]oct-6-ene 6-oxides, have been assembled diastereoselectively via acetyldihydropyrans, products of one-pot self-organization of two molecules of ketones and two molecules of acetylene, which after oximation undergo acid-catalyzed ring closure. The proposed mechanism includes the enol double-bond protonation, followed by intramolecular cyclization involving the interaction of the carbocation formed with a nitrogen atom. A broad range of substrates tolerate this facile transformation, in which the bridgehead nitrones were isolated in high yields.
RESUMEN
A straightforward acetylene-based scalable strategy for the synthesis of highly functionalized N-aminoindoles has been discovered. This pot-, atom-, step-, and energy-economic strategy includes two simple stages: (i) a one-pot multimolecular (2 + 2) diastereoselective assembly of 6,8-dioxabicyclo[3.2.1]octanes (6,8-DOBCOs) from acetylene gas and ketones in the KOH/DMSO two-phase superbase catalytic system and (ii) a mild (rt, CF3COOH) cascade transformation of 6,8-DOBCOs under the action of hydrazines to afford N-(arylamino)-3-(acylpropyl)indoles in good yields.
RESUMEN
Pharmaceutically related bridgehead dihydro-1,3,4-oxadiazines are synthesized in up to 94% yield by the acid-catalyzed diastereoselective reaction of hydrazine hydrate with 6,8-dioxabicyclo[3.2.1]octanes (6,8-DOBCOs), the products of the superbase-promoted self-organization of acetylene with ketones. The synthesis covers a diverse range of alkylaromatic ketones having F-, Cl-, Br-, alkoxy-, CF3- and aryl substituents in different positions of the aromatic rings.
RESUMEN
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 KOBut/DMSO superbase system (105 °C, 1.5 h) to stereoselectively give the corresponding E-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 Z,3 E)-diene substituent.
RESUMEN
The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBut/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.
RESUMEN
KO(t)Bu/DMSO-promoted C-H functionalization of acetylarenes with arylacetylenes (100 °C, 30 min), generating ß,γ-ethylenic ketones, triggers upon further heating (100 °C, 4 h, with or without acidifying additive) the cascade assembly of acyl terphenyls and higher polyaromatics in good yields.
RESUMEN
The sequential reaction of ketones with arylacetylenes and hydroxylamine in the presence of KOBu(t)/DMSO followed by the treatment of the reaction mixture with H(2)O and KOH leads to Δ(2)-isoxazolines in up to 88% yield.