Neue Synthesen mit Oniumsalzen von Aza‐arenen

Abstract

Wirkungsvolle Synthesen in Abwesenheit starker Sauren und Basen sind unter Verwendung 2halogenierter Pyridinium-, Benzoxazolium-, Benzothiazolium-und Pyrimidiniumsalze gelungen. Die Aktivierung von Carbonsauren oder Alkoholen mit diesen Oniumsalzen fiihrt zu 2-Acyloxy-bzw. 2-Alkoxy-Zwischenstufen, die sich z. B. zu Estern, Amiden, Thiolestern, (makrocyclischen) Lactonen, Saurefluoriden, Olefinen, Allenen, Carbodiimiden, Isocyanaten, Isothiocyanaten, Nitrilen und Isocyaniden umsetzen lassen. Hervorzuheben ist die Moglichkeit, mit den Oniumsalzen stereospezifische Synthesen (unter Inversion der Konfiguration) durchzufuhren. 798 0 Verlag Chemie, GmhH, 0.6940 Wernherm, 1979 ~~ ~ 0044-R249/79/1010-0798 $ 02 50/0 Angew Chem 91. 798-812 (1979)

N -substituted 4-(4-carboxyphenoxy)benzamides. Synthesis and Evaluation as Inhibitors of Steroid-5α-reductase Type 1 and 2

“…The finding that the adamantyl inhibitor (26) is more active than both the cyclohexyl and the dicyclohexyl compound supports the hypothesis that a bulky substituent shows a greater inhibitory potency but, at the same time, implies that there is an upper limit for the bulkiness. Furthermore it becomes clear that secondary amides (21,24,26,27), show a better inhibitory activity than tertiary amides (22,23,28). The only exception to this rule is compound 25.…”

“…Yield 57%, white powder, mp 157 -1598C. 1 N-Phenyl-4-(4 0 carboxyphenoxy)benzamide (24) Synthesised from N-phenyl-4-(4 0 -formylphenoxy)-benzamide (24a N,N-Diphenyl-4-(4 0 -carboxyphenoxy)benzamide (25) Synthesised from N,N-diphenyl-4-(4 0 -formylphenoxy)benzamide (25a). Purified by recrystallisation (hexane/ethyl acetate).…”

Straightforward Access to a Structurally Diverse Set of Oxacyclic Scaffolds through a Four‐Component Reaction

“…Similarly, by using glyoxylic acid ( 3 b ) we obtained the compound 5 b in high yield (83 %, isomer ratio 70:30). Purification of this mixture afforded the major component and allowed the stereochemical elucidation of the process11 by conversion of 5 b into the major isomer of 5 a with EtOH and Sc(OTf) 3 and subsequent esterification using Mukaiyama's reagent 12. As expected, the approach of the imine to the enol ether was similar in both cases whereas the trapping of the oxocarbonium ion took place with opposite stereoselectivity (Scheme ).…”

Thiazolium and Benzothiazolium Ionic Liquids

“…and iodide (117, X = I -) with dialdehydes such as pphenylenedicarbaldehyde, 2,5-dimethoxy-p-phenylenedicarbaldehyde, thiophene-2,3 dicarbaldehyde (scheme-33) (Kossmehl et al 1979). In the same year Mukaiyama (1979) studied that the benzothiazolium compounds can be used to activate the carboxylic acids or alcohols to give 2-acyloxy or 2-alkoxy intermediates, which can be converted into esters, thioesters, amides, lactones, acid fluorides, isocyanates, etc (Mukaiyama 1979). …”