Chiral hypervalent iodine compounds

Chiral Hypervalent Organo-Iodine(III) Compounds

“…This evaluation of the chiral hypervalent iodine reagents shows that increasing the size of the ortho substituent from R ϭ H through R ϭ Me (1a) to R ϭ Et (1b) results in an increased selectivity in the dioxytosylation of styrene. The unsubstituted reagent yielded the product 9 with 33% ee, [19] whereas using 1a and 1b, 9 was obtained with 47% and 65% ee, respectively. Likewise, the ortho-methoxy compound gave an ee of 52% in the dioxytosylation of styrene.…”

“…[19,20] It was shown previously that the placement of a chiral moiety ortho to the iodine atom on the aromatic ring results in compounds that react selectively with alkenes. [19] These investigations showed a 1-methoxyethyl substituent analysis and ab initio calculations on a hypervalent iodine salt have been used to develop a model for rationalizing the stereoselectivities in these reactions with chiral hypervalent iodine reagents. In this model, high enantiomeric excess in the reaction correlates with the relative population of a conformation in which a methyl group on the asymmetric carbon atom is in the axial position.…”

Synthese von Indolen durch ein modifiziertes Koser‐Reagens

“…Diese Befunde illustrieren die schnelle und produktive Reaktion einer großen Substratbandbreite, die derjenigen der metallvermittelten Prozesse überlegen ist. [19] Der gleiche Ablauf wurde für entsprechende intramolekulare Oxidationsreaktionen von Alkenen mit Methylcarbamaten angenommen, wobei diese Umwandlungen lediglich in einem Übersichtsartikel [13c] diskutiert wurden. Eine gewisse Limitierung wurde für die Synthese des 4-Methylindols 2 z gefunden.…”

α-Functionalization of Carbonyl Compounds Using Hypervalent Iodine Reagents

“…In 1997, Wirth and Hirt published the synthesis of several chiral HTIBs, together with the first application of such reagents in the asymmetric α-tosyloxyation of ketones (Scheme 16, compounds 2 and 3). [46] Optimization of the chiral reagents by varying the substituents on the aromatic ring led to ees up to 28% (Scheme 16, compounds 4-6). [47] Further investigations showed that increased steric bulk of the ortho substituent improved the enantioselectivity.…”