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

A One-Pot Approach to Δ²‑Isoxazolines from Ketones and Arylacetylenes

The sequential reaction of ketones with arylacetylenes and hydroxylamine in the presence of KOBu^<i>t</i>/DMSO followed by the treatment of the reaction mixture with H₂O and KOH leads to Δ²-isoxazolines in up to 88% yield

Thermodynamic investigation of G2 and G4 siloxane dendrimers with trimethylsilyl terminal groups

In this work, we report results of the calorimetric study of the second (G2[OSi(CH3)3]12) and fourth (G4[OSi(CH3)3]48) generation siloxane dendrimers with trimethylsilyl terminal groups. The heat capacities of dendrimers were precisely measured in the temperature range T = (5–520) K using a fully automated adiabatic calorimeter and a heat-flux differential scanning calorimeter. In the above temperature interval, the physical transformations of the studied compounds were detected, and its thermodynamic characteristics were determined. The fundamental thermodynamic functions (the enthalpy [H°(T) − H°(0)], the entropy [S°(T) − S°(0)], the Gibbs energy [G°(T) − H°(0)]) of dendrimers were calculated over the range from T → 0 to 520 K using the experimentally determined heat capacities of the investigated compounds. The standard entropies of formation of dendrimers G2[OSi(CH3)3]12 and G4[OSi(CH3)3]48 were evaluated at T = 298.15 K. The obtained thermodynamic data of the investigated dendrimers were compared with those of the studied earlier siloxane dendrimers G1[OSi(CH3)3]6 and G3[OSi(CH3)3]24, which represent the structurally related homologous series of organosilicon dendrimers. As a result, the dependences between thermodynamic properties of the studied siloxane dendrimers and their molecular mass were established

Synthesis of Acyl Terphenyls and Higher Polyaromatics via Base-Promoted C–H Functionalization of Acetylarenes with Arylacetylenes

KO<i>^t</i>Bu/DMSO-promoted C–H functionalization of acetylarenes with arylacetylenes (100 °C, 30 min), generating β,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

True Molecular Composites: Unusual Structure and Properties of PDMS-MQ Resin Blends

Poly(dimethyl siloxane)-MQ rubber molecular composites are easy to prepare, as it does not require a heterophase mixing of ingredients. They are characterized by perfect homogeneity, so they are very promising as rubber materials with controllable functional characteristics. The manuscript reveals that MQ resin particles can significantly, more than by two orders of magnitude, enhance the mechanical properties of poly(dimethyl siloxane), and, as fillers, they are not inferior to aerosils. In the produced materials, MQ particles play a role of the molecular entanglements, so rubber molecular weight and MQ filler concentration are the parameters determining the structure and properties of such composites. Moreover, a need for a saturation of the reactive groups and minimization of the surface energy of MQ particles also determine the size and distribution of the filler at different filler rates. An unusual correlation of the concentration of MQ component and the interparticle spacing was revealed. Based on the extraordinary mechanical properties and structure features, a model of the structure poly(dimethyl siloxane)-rubber molecular composites and of its evolution in the process of stretching, was proposed

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