Manifestations of the Alder−Rickert Reaction in the Structures of Bicyclo[2.2.2]octadiene and Bicyclo[2.2.2]octene Derivatives

Abstract

The Alder-Rickert ethylene extrusion reaction manifests in the ground state structures of compounds 9-12 which contain the bicyclo[2.2.2]octadiene moiety and compounds 13, 14, and 17-20 which contain the bicyclo[2.2.2]octene moiety. A significant decrease of the 13C-13C one-bond coupling constants for the C-C bonds, which break in this fragmentation reaction, suggests lengthening, and hence weakening of these bonds. In the unsymmetrical systems these effects are also shown to be associated with strengthening of the CH2-CH2 bond, which is ultimately lost from the molecule as ethylene. Low-temperature crystal structures of compounds 9-12 and 16 provide evidence for similar crystal packing requirements of the CH2-CH2 and CH=CH moieties.

Ring Opening Metathesis Polymerization of Bicyclic α,β‐Unsaturated Anhydrides for Ready‐to‐be‐grafted Polymers Having Tailored pH‐Responsive Degradability

“…[10] Moreover,the possible ROMP monomers having the structure of maleic acid anhydride derivative can be readily synthesized by the Diels-Alder reaction. [11] Theexpected polymers may possess the amine-reactive anhydrides in every repeating unit and be well "ready-to-be-grafted" with amine-possessing molecules in high density.The densely grafted polymers may release the grafted molecules in pH-dependent manners.O fc ourse,w e can tune the pH-responsive release kinetics of the grafted molecules by controlling the angle between cis-substituents. [6] After confirmation of our main concept for the synthesis of the ready-to-be-grafted ROMP polymers having tailored pHresponsive degradability,w ec hecked the potential of the polymers for pH-responsive delivery of am odel drug, alendronate,invitro.…”

Hyperconjugation Involving Strained Carbon–Carbon Bonds. Structural Analysis of Ester and Ether Derivatives and One-Bond13C–13C Coupling Constants of α- and β-Nopinol

“…Other general experimental details have been reported elsewhere. 29 General Procedure A: Reaction of Alcohols with 4-Fluoronitrobenzene. Potassium hydride (1.0 equiv) was added to a solution of alcohol (1.0 equiv) in anhydrous THF.…”

Cyclic Anhydrides as Powerful Tools for Bioconjugation and Smart Delivery

“…The anhydride obtained with cyclopentadiene can undergo ethylene extrusion at 110°C by Alder-Rickert reaction. 131 Polymers from bicyclic α,β-unsaturated anhydrides could be obtained by ring opening metathesis polymerization (ROMP), and the furan ring could be cleaved by FeCl3, as it has an allyl ether structure. 132 Scheme 11: synthesis of bicyclic α,β-unsaturated anhydrides by Diels-Alder cycloaddition.…”

“…Their synthesis can be realized by Diels–Alder cycloaddition followed by reaction with acetic anhydride (Scheme ). The anhydride obtained with cyclopentadiene can undergo ethylene extrusion at 110 °C by Alder-Rickert reaction . Polymers from bicyclic α,β-unsaturated anhydrides could be obtained by ring-opening metathesis polymerization (ROMP), and the furan ring could be cleaved by FeCl 3 , as it has an allyl ether structure …”