Straightforward Synthesis of Poly(dimethylsiloxane) Phases with Immobilized (1R)‐3‐(Perfluoroalkanoyl)camphorate Metal Complexes and Their Application in Enantioselective Complexation Gas Chromatography

Abstract

A straightforward synthesis of novel chiral polysiloxane‐based metal stationary phases immobilized through a propylenoxy linker (Chirasil‐Metal‐OC3) to the polymeric backbone is presented. Synthesis was accomplished in six steps with high overall yields starting from commercially available, enantiopure (+)‐(1S)‐camphorsulfonic acid. Two different approaches towards Chirasil‐Metal phases featuring either a propylenoxy or propylenthio linker used for immobilization through hydrosilylation are presented. Furthermore, a new protocol for the fluoroacylation, which is one of the key steps in the synthesis of (1R)‐3‐(perfluoroalkanoyl)camphorate metal complexes, was developed to improve the isolation and overall yield. The immobilization of (1R,4S)‐10‐(allyloxy)‐3‐(heptafluorobutanoyl)camphor – 10‐(allyloxy)‐hfbc – onto polysiloxanes as well as the incorporation of nickel(II), oxovanadium(IV), europium(III), and lanthanum(III) was characterized by FT ATR IR and NMR spectroscopy. Overall, seven different Chirasil‐Metal‐OC3 polymers with different separation properties were prepared by metal incorporation and variation of the amount of immobilized (1R,4S)‐10‐(allyloxy)‐3‐(heptafluorobutanoyl)camphor (10‐allyloxy‐hfbc: 3.5, 10.2, and 20.0 %). Their performance in enantioselective complexation gas chromatography was systematically studied and excellent enantioselectivity was found for Chirasil‐Nickel‐OC3. Separation of 29 small‐sized compounds, encompassing, among others, epoxides, substituted alkenes and alkynes as well as alcohols and amides, was achieved with high separation factors α. The synthetic strategy, enantiomer separations and thermal stability (up to 160 °C) demonstrates the versatility of the newly derived Chirasil‐Metal‐OC3 phases.

Synthesis and preliminary biological evaluations of (+)-isocampholenic acid-derived amides

“…Thus, following a slightly modified literature procedure [10], treatment of 6 with PPh 3 /I 2 in toluene under thermal conditions afforded 10-iodocamphor (7) in 62% yield and 82 % purity; the O=PPh 3 side-product (18 % yield) did not interfere with the upcoming transformation. Next, 10-iodocamphor (7) was subjected to the base-induced (KOH) Grob fragmentation, yielding the desired acid 1 [12] in 76 % yield.…”

“…On the other hand, Money and co-workers applied Grob fragmentation reactions of suitably functionalized 10-bromocamphor derivatives for the preparation of various natural products and their analogues [4,5,9]. (+)-Isocampholenic acid (1) is conveniently prepared from 10-bromo-or 10-iodocamphor [10] by treatment with KOH via Grob [11] fragmentation [12]. (+)-α-Campholenic acid (2) [13], on the other hand, can easily be prepared via Retro-Prins fragmentation of (S)-(+)-camphorsulfonic acid [14] by KOH fusion at 200-220 • C for 5 min [15].…”

Effect of Stereochemistry of Avermectin‐Like 6,6‐Spiroketals on Biological Activities and Endogenous Biotransformations in Streptomyces avermectinius

“…Um hohe Enantiomerenreinheiten zu validieren, eignet sich das spiegelbildliche Chirasil‐ D ‐Val, das die Elutionsreihenfolge umkehrt. Chirasil‐Metall (Abbildung 2, Mitte) dient zur Enantiomerentrennung durch GC16,17 und SFC (Superkritische Fluidchromatographie, Metall = NiII)16 sowie als löslicher polymerer enantioselektiver Katalysator, der durch Fällung zurückgewonnen wird (Metall = VOIV 18. Zudem wird es in der Reaktions‐GC verwendet mit Metall = GdIII 19.…”

Direkte Beobachtung alternativer Reaktionswege an einzelnen Molekülen

“…[27][28][29] Die Wahl der spektralen Bereiche der Einzelmoleküldetektion legt nahe, dass die beobachtete spektrale Verschiebung der Umwandlung der Doppelbindung in 3 zum Epoxid 4 entspricht (Abbildung 2 c,d). [27][28][29] Die Wahl der spektralen Bereiche der Einzelmoleküldetektion legt nahe, dass die beobachtete spektrale Verschiebung der Umwandlung der Doppelbindung in 3 zum Epoxid 4 entspricht (Abbildung 2 c,d).…”