Isobenzofulvene

Abstract

der Kettenmolekiile als Punkte. Die Rostebenen sind parallel zur b-Achse angeordnet. Der nachste Abstand fur zwei identische Rostebenen im orthorhombischen Gitter wurde aus den Rontgenreflexen zu 10,9 A berechnet. In Analogie zum Seidenfibroin ist anzunehmen, dab auch im Gitter der Poly-P-aminobuttersaure erst die ubernachste Rostebene rnit der ersten identisch ist, wie es die Zeichnung andeutet. Die Elementarzelle enthalt dann vier (3-Aminosaure-Einheiten. Die hieraus berechnete Kristalldichte stimmt mit der beobachteten gut uberein.Die Elementarzelle des Seidenfibroins "8,191 enthalt acht a-Aminosaureeinheiten. Der Unterschied in den Elementarzellen besteht im wesentlichen darin, daO beim Seidenfibroin erst eine Dipeptideinheit der Abmessung 7,O A zur Identitat in der Polypeptidkette fuhrt, wahrend bei Poly-$-aminobuttersaure bereits nach einer Einheit des Bausteins, also im Abstand von 4,6 A, die Identitat wiederkehrt.

The Game of Electrons: Organocatalytic Higher‐Order Cycloadditions Involving Fulvene‐ and Tropone‐Derived Systems

“…[17] Structurally related, achiral amino isobenzofulvenes were previously reported to participate in [10+ +2]-cycloadditions with N-phenylmaleimide. [18] In Jørgensen's report, the reactionw as performed in presence of a C 2 -symmetric aminocatalyst 4b to provide highly peri-, diastereo-, and enantioselective formation of chiral benzonorbornene scaffolds 15.T he aldehyde moietyi nt he originally formed products was reduced in ao ne-pot manner with NaBH 4 to provide more stable alcohols 15 and to ease the isolation. In this work, the mechanistic study by DFT calculations suggested that the higher-order cycloadditionp roceeded via as tepwise reactiona nd the stereoselectivity was governed by the kinetics of the first bond-forminge vent.…”

Organocatalytic Enantioselective Higher‐Order Cycloadditions of In Situ Generated Amino Isobenzofulvenes

“…[5] An amino substituent on the exocycliccarbon atom stabilized the isobenzofulvenes by increasing the aromatic character.T he depicted amino isobenzofulvene was found to form am ixture of [10+ +2] cycloadducts with N-phenylmaleimide (Scheme 1). [5] An amino substituent on the exocycliccarbon atom stabilized the isobenzofulvenes by increasing the aromatic character.T he depicted amino isobenzofulvene was found to form am ixture of [10+ +2] cycloadducts with N-phenylmaleimide (Scheme 1).…”

“…In 1968, the first isobenzofulvenes were utilized in cycloadditions by Hafner and Bauer. [5] An amino substituent on the exocycliccarbon atom stabilized the isobenzofulvenes by increasing the aromatic character.T he depicted amino isobenzofulvene was found to form am ixture of [10+ +2] cycloadducts with N-phenylmaleimide (Scheme 1). In the following years Warrener et al explored the periselectivity of isobenzofulvenes and found them to react as both 8p-a nd 10p-electron components in [8+ +2],[ 8 + +6],a nd [10+ +8] cycloadditions.…”