Aerobic Catalytic Features in Photoredox- and Copper-Catalyzed Iodolactonization Reactions

Mechanistic evaluations and comparison of two important aerobic catalytic oxidation processes, aerobic copper catalysis and photoredox catalysis, are performed. Interesting and distinct catalytic behaviors were observed for a common reaction of iodolactonization of alkenoic acids. Namely, the aerobic copper catalysis requires the formation of a copper carboxylate, whereas the aerobic photoredox catalysis requires the addition of proton sources to proceed to completion. Furthermore, the iodolactone products obtained from these catalytic processes are extensively derivatized to a number of functionalized lactones, including aryl lactones generated from the nickel-catalyzed reductive coupling with aryl halides.

Regioselective dehydration of α-hydroxymethyl tetrahydrofurans using Burgess' reagent under microwave irradiation

We here present a highly efficient and high yielding procedure for the preparation of 2-vinyl tetrahydrofurans starting from α-hydroxymethyl tetrahydrofurans. Best results for this dehydration were achieved using Burgess' reagent in dioxane under microwave irradiation. A range of functional groups as well as different cyclic and bicyclic frameworks were found to be compatible with the reaction conditions. The desired products were obtained within minutes in good to high yields and excellent regioselectivity.

W. Stark CBWS. Short and highly efficient synthesis of lipid peroxidation inhibitor pyrrolostatin and some analogues thereof

A highly efficient and scalable synthesis of the potent lipid peroxidation inhibitor pyrrolostatin is presented together with strategies to modify the key structural subunits.

Ruthenium tetroxide and perruthenate chemistry. Recent advances and related transformations mediated by other transition metal oxo-species

In the last years ruthenium tetroxide is increasingly being used in organic synthesis. Thanks to the fine tuning of the reaction conditions, including pH control of the medium and the use of a wider range of co-oxidants, this species has proven to be a reagent able to catalyse useful synthetic transformations which are either a valuable alternative to established methods or even, in some cases, the method of choice. Protocols for oxidation of hydrocarbons, oxidative cleavage of C-C double bonds, even stopping the process at the aldehyde stage, oxidative cleavage of terminal and internal alkynes, oxidation of alcohols to carboxylic acids, dihydroxylation of alkenes, oxidative degradation of phenyl and other heteroaromatic nuclei, oxidative cyclization of dienes, have now reached a good level of improvement and are more and more included into complex synthetic sequences. The perruthenate ion is a ruthenium (VII) oxo-species. Since its introduction in the mid-eighties, tetrapropylammonium perruthenate (TPAP) has reached a great popularity among organic chemists and it is mostly employed in catalytic amounts in conjunction with N-methylmorpholine N-oxide (NMO) for the mild oxidation of primary and secondary alcohols to carbonyl compounds. Its use in the oxidation of other functionalities is known and recently, its utility in new synthetic transformations has been demonstrated. New processes, synthetic applications, theoretical studies and unusual transformations, published in the last eight years (2006-2013), in the chemistry of these two oxo-species, will be covered in this review with the aim of offering a clear picture of their reactivity. When appropriate, related oxidative transformations mediated by other metal oxo-species will be presented to highlight similarities and differences. An historical overview of some aspects of the ruthenium tetroxide chemistry will be presented as well.