Reaktionen von trans‐Cycloocten und von 7‐Methoxy‐1,3‐dioxa‐5(E)‐cycloocten mit Allenen und mit Chlorsulfonylisocyanat. Bildung der ersten trans‐anellierten Methylencyclobutane. Reaktion von Allen als En‐Komponente
“…The stereochemistry of this reaction is such that one can only obtain the trans isomer if a trans cycloalkane is used as reactant. The smallest isolable trans cycloalkene is trans -cyclooctene ( 17 ), which has been used to prepare the β-lactam 18 (eq 5).…”
Lactams were synthesized by the carbonylative ring expansion of aziridines catalyzed by dicobalt octacarbonyl under CO pressure. The active catalyst, cobalt tetracarbonyl anion, induces nucleophilic ring opening of the heterocycle, resulting in inversion of configuration. The regio-and stereospecificity of this reaction resulted in the synthesis of the first highly strained trans-7-azabicyclo[4-2-0]octan-8-one derivatives.111
“…The stereochemistry of this reaction is such that one can only obtain the trans isomer if a trans cycloalkane is used as reactant. The smallest isolable trans cycloalkene is trans -cyclooctene ( 17 ), which has been used to prepare the β-lactam 18 (eq 5).…”
Lactams were synthesized by the carbonylative ring expansion of aziridines catalyzed by dicobalt octacarbonyl under CO pressure. The active catalyst, cobalt tetracarbonyl anion, induces nucleophilic ring opening of the heterocycle, resulting in inversion of configuration. The regio-and stereospecificity of this reaction resulted in the synthesis of the first highly strained trans-7-azabicyclo[4-2-0]octan-8-one derivatives.111
Durch einfaches Erhitzen einer Dien/Dienophil‐Vorstufe sind wahlweise g‐Mengen des [6]Belten‐Derivats 1 oder eines bandartigen Polymers erhältlich. Im Kristall liegt das stereochemisch einheitliche 1 als abgeflachter, doppelsträngiger Ring vor. Das Bandpolymer (Polymerisationsgrad 24–330!) bildet wahrscheinlich „zweidimensionale Knäuel”︁. R =
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