cis-Stilbene (1) has been epoxidized by a set of diverse oxygen donors [OxD], catalyzed by the Mn(III)(salen)X complexes 3 (X = Cl, PF(6)), to afford a mixture of cis- and trans-epoxides 2. The cis/trans ratios range from 29:71 (extensive isomerization) to 92:8, which depends both on the oxygen source [OxD] and on the counterion X of the catalyst. When (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)-benzene (4) is used as substrate, a mechanistic probe which differentiates between radical and cationic intermediates, no cationic ring-opening products are found in this epoxidation reaction; thus, isomerized epoxide product arises from intermediary radicals. The dependence of the diastereoselectivity on the oxygen source is rationalized in terms of a bifurcation step in the catalytic cycle, in which concerted Lewis-acid-activated oxygen transfer competes with stepwise epoxidation by the established Mn(V)(oxo) species. The experimental counterion effect is attributed to the computationally assessed ligand-dependent reaction profiles and stereoselectivities of the singlet, triplet, and quintet spin states available to the manganese species.

Flexible transparent barrier films are required in various fields of application ranging from flexible, transparent food packaging to display encapsulation. Environmentally friendly, waterborne polymer–clay nanocomposites would be preferred but fail to meet in particular requirements for ultra high water vapor barriers. Here we show that self-assembly of nanocomposite films into one-dimensional crystalline (smectic) polymer–clay domains is a so-far overlooked key-factor capable of suppressing water vapor diffusivity despite appreciable swelling at elevated temperatures and relative humidity (R.H.). Moreover, barrier performance was shown to improve with quality of the crystalline order. In this respect, spray coating is superior to doctor blading because it yields significantly better ordered structures. For spray-coated waterborne nanocomposite films (21.4 μm) ultra high barrier specifications are met at 23 °C and 50% R.H. with oxygen transmission rates (OTR) < 0.0005 cm3 m–2 day–1 bar–1 and water vapor transmissions rates (WVTR) of 0.0007 g m–2 day–1. Even in the most challenging environments (38 °C and 90% R.H.), values as low as 0.24 cm3 m–2 day–1 bar–1 and 0.003 g m–2 day–1 were found for OTR and WVTR, respectively.

The Ti-catalyzed, asymmetric oxidation of alkyl aryl sulfides by enantiomerically pure hydroperoxides (ee >99%) has been examined. Enantioselectivities with ee values up to ca. 80% were achieved for the oxygen transfer from (S)-(-)-1-phenylethyl hydroperoxide 2a to methyl phenyl and methyl p-tolyl sulfide 1a in CCl 4 as solvent, but with much overoxidation to the corresponding sulfone 4. Detailed mechanistic studies showed that the enantioselectivity of the sulfide 1a oxidation results from a combination of a rather low (ee values <20%) asymmetric induction in the sulfoxidation and an effective kinetic resolution (ee values ca. 80% at 85% sulfide conversion) of the sulfoxide 3a by enantioselective oxidation to the sulfone 4a. The overoxidation (loss of chemoselectivity) is due to sulfoxide coordination to the Ti metal to generate a template in which the oxygen atom is intramolecularly transferred from the bound and activated, optically active hydroperoxide to the ligated sulfoxide in a stereocontrolled manner.

The catalytic oxidation of the phenyl-substituted cis alkenes 1a,b by the Mn III (salen)X complexes 3a−f with iodosyl benzene (PhIO) as oxygen source affords the corresponding epoxides 2a,b in cis/trans ratios of 79:21 to 26:74. The diastereoselectivity (cis/trans ratio) depends on the counterion of the Mn III (salen)X complexes 3a−f. Thus, for the complexes 3a−c (Cl − , Br − and AcO − as ligating counterions) extensive iso-Eur.

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