An efficient preparative method for the synthesis of siloxanols based on aerobic Co(OAc)2 or Cu(OAc)2/NHPI-catalyzed oxidation of hydride siloxanes has been proposed.

Stereochemically inert and positively charged chiral complexes of cobalt(III) prepared from Schiff bases derived from chiral diamines and salicylaldehydes were shown to be efficient catalysts of the benchmark asymmetric phase‐transfer Michael addition of nine activated olefins to O’Donnell’s substrate. The reaction products had enantiomeric purities of up to 96%. DFT calculations were invoked to rationalize the stereochemistry of the addition.magnified image

Interaction of the copper, {[3,5-(CF(3))(2)Pz]Cu}(3), and silver, {[3,5-(CF(3))(2)Pz]Ag}(3), macrocycles [3,5-(CF(3))(2)Pz = 3,5-bis(trifluoromethyl)pyrazolate] with cyclooctatetraeneiron tricarbonyl, (cot)Fe(CO)(3), was investigated by IR and NMR spectroscopy for the first time. The formation of 1:1 complexes was observed at low temperatures in hexane. The composition of the complexes (1:1) and their thermodynamic characteristics in hexane and dichloromethane were determined. The π-electron system of (cot)Fe(CO)(3) was proven to be the sole site of coordination in solution and in the solid state. However, according to the single-crystal X-ray data, the complex has a different (2:1) composition featuring the sandwich structure. The complexes of ferrocene with copper and silver macrocycles have a columnar structure (X-ray data).

Stereochemically inert and positively charged chiral complexes of Co(III) were shown to catalyze the asymmetric epoxidation of chalcones with H 2 O 2 under phase transfer conditions. The reaction products had enantiomeric purities of up to 55%. It was also shown that complex 1a Icatalyzed the coupling reaction of a resulting epoxide with CO 2 (conversion 72%).Enantiomerically enriched α,β-epoxy ketones are versatile chiral building blocks for access to natural compounds and drugs in medicinal chemistry. 1,2 They can be converted into many types of useful chiral compounds, such as αhydroxy, β-hydroxy, α,β-dihydroxy carbonyl compounds, as well as epoxy alcohols. 3 The basic method of producing the enantiomerically enriched epoxy ketones is the asymmetric oxidation of activated olefins. 4 By far the most attractive method for the preparation of epoxy ketones is asymmetric epoxidation of chalcones. 5 A green and most cost effective approach is to use hydrogen peroxide as the oxidizing agent, 4e because the only by-products of the reaction is are water and molecular oxygen. The catalytic protocols usually employ either chiral metal complexes of iron 6 and manganese 7 or chiral organocatalysts, in particular, those operating under phase transfer conditions. 8 Recently we successfully elaborated chiral, positively charged, stereochemically inert complexes of Co(III) as chiral phase transfer catalysts for efficient asymmetric alkylation of a glycine Schiff base ester (O'Donnell substrate) with alkyl halides. 9a In addition, the family of the complexes could be successfully applied for the asymmetric 1,4-addition of O'Donnell's substrate to activated olefins. 9b The convincing evidence was put forward proving the complexes functioned in the reactions as "organic catalysts in disguise". 10 We believed further attempts at employing the catalysts in classical asymmetric reactions of C-C formation could be of interest.Herein we describe the use of octahedral stereochemically inert and positively charged "chiral-at-metal" Co(III) complexes 9 (depicted on Fig. 1) of both Λ− and Δ-configurations. The complexes were used as catalysts for the asymmetric epoxidation of chalcones under phase-transfer conditions and some preliminary results on the CO 2 coupling with the forming epoxides, promoted by the same complexes.

This study reports intriguing features in the self-assembly of cage copper(II) silsesquioxanes in the presence of air. Despite the wide variation of solvates used, a series of prismatic hexanuclear Cu 6 cages (1−5) were assembled under mild conditions. In turn, syntheses at higher temperatures are accompanied by side reactions, leading to the oxidation of solvates (methanol, 1-butanol, and tetrahydrofuran). The oxidized solvent derivatives then specifically participate in the formation of copper silsesquioxane cages, allowing the isolation of several unusual Cu 8 -based (6 and 7) and Cu 6 -based (8) complexes. When 1,4-dioxane was applied as a reaction medium, deep rearrangements occurred (with a total elimination of silsesquioxane ligands), causing the formation of mononuclear copper(II) compounds bearing oxidized dioxane fragments (9 and 11) or a formate-driven 1D coordination polymer (10). Finally, a "directed" self-assembly of sil-and germsesquioxanes from copper acetate (or formate) resulted in the corresponding acetate (or formate) containing Cu 6 cages (12 and 13) that were isolated in high yields. The structures of all of the products 1−13 were established by singlecrystal X-ray diffraction, mainly based on the use of synchrotron radiation. Moreover, the catalytic activity of compounds 12 and 13 was evaluated toward the mild homogeneous oxidation of C 5 −C 8 cycloalkanes with hydrogen peroxide to form a mixture of the corresponding cyclic alcohols and ketones.