Sulfonamide Ligands from Chiral Aziridines − Application to the Titanium-Mediated Addition of Diethylzinc to Benzaldehyde

The Reactions of Alkenes with Phenyl-N-triflylimino-λ3-iodane: Solvent and Oxidant Impact

The reactions of alkenes with phenyl-N-triflylimino-λ3-iodane PhI=NTf (1) have been studied in different conditions. In methylene chloride, in the presence of N-halosuccinimides, the products of mono and bis-triflamidation were obtained. In MeCN, the product of bromotriflamidation (with NBS) with solvent interception or of bis-triflamidation (with NIS) is formed. The reaction with trans-stilbene in acetonitrile with NBS gave rise to cyclization to 2-methyl-4,5-diphenyl-1-triflyl-4,5-dihydro-1H-imidazole. In contrast, with NIS as an oxidant, both in CH2Cl2 and MeCN, the major product was 2,3-diphenyl-1-triflylaziridine formed in good yield. With NBS, aziridine is also formed but as a minor product, the major one being a mixture of diastereomers of the product of bromotriflamidation. The reaction of compound 1 with vinylcyclohexane in methylene chloride affords the mixtures of regioisomers of the products of halotriflamidation, whereas in acetonitrile, the products of solvent interception and cyclization to the imidazoline are formed. A mechanism explaining the formation of all isolated products is proposed.

Development of C2-Symmetric Chiral Bifunctional Triamines: Synthesis and Application in Asymmetric Organocatalysis

The synthesis and application of a newly designed C₂-symmetric chiral bifunctional triamine family ( C₂-CBT) is reported. These enantiopure chiral triamine scaffolds can be accessed in multigram amounts from simple amino acids while avoiding chromatographic purification. As a proof of principle, C₂-CBT has been studied in the aldol reaction of cyclic ketones with isatins, with the target tertiary alcohols being formed in a highly efficient manner. Catalyst recovery by simple extraction techniques and subsequent reuse has been performed.

Modular multidentate phosphine ligands: application to palladium-catalyzed allylic alkylations

Multidentate phosphines were readily obtained by reaction of chiral multidentate amines, prepared via ring opening of (S)-N-tosyl-2-isopropylaziridine with ammonia, primary, and secondary amines, with achiral phosphorus containing building blocks. The phosphines were used in palladium-catalyzed alkylation of rac-3-cyclohexenyl and cyclopentenyl carbonates. The enantioselectivity and reactivity were largely dependent on the structure of the amine core of the ligands. Up to 88% ee was observed in reactions with the six-membered substrate.

Controlled Microwave Heating in Modern Organic Synthesis

Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.