Ring closure reactions of bifunctional chain molecules

Publisher Summary This chapter focuses that the field of intramolecular reactions is a mature area in which the merging of concepts from both physical organic chemistry and polymer chemistry leads to a unified treatment of cyclization rates and equilibria in terms of a few simple generalizations and theories. It is concerned with reaction rates, equilibria, and mechanisms of cyclization reactions of chain molecules. It discusses that parallel to the search for synthetic methods to make rings of all sizes, kinetic studies have appeared with the aim of providing insight into physical aspects of ring closure. A significant portion of the evidence available on the kinetics of intramolecular reactions falls in the domain of neighboring group participation. The term is sufficiently wide to encompass “all intramolecular reactions and all reactions that involve nonelectrostatic through-space interactions between groups in the same molecule.” However, the most common types of neighboring group participation involve nucleophilic participation either with or without anchimeric assistance and intramolecular acid and base catalysis. The chapter explores that intramolecular catalysis phenomena have attracted much attention, both from the experimental and theoretical points of view, not only on account of their inherent mechanistic interest, but also because they are believed to model the extraordinary efficiency of enzyme catalysis.

Intramolecular Reactions of Chain Molecules

The fluorescence spectra of a series of <x,cu-di-(l-pyrenyl)alkanes Py(CH2)7¡P¡/ with re = 2 to 16 and 22, nearly all contain emissions from an intramolecular excimer, when measured in a 1 · -5 M solution in methylcyclohexane at room temperature. It is shown that the emissions do not arise from preformed dimers in the ground state. The intensity ratio of the excimer and monomer fluorescence as a function of chain length, which has a clear minimum for re = 7 and shows an alternating property for larger re, strongly resembles the dependence of the yields of organic ring closure reactions on ring size. For re = 2 and = 4—9 a blue shift of the energy of the excimer emission maximum, relative to re = 3, is observed. Also with an , -diphenylalkane an intramolecular excimer emission is found for longer alkane chains, with re = 13. For l,3-di-(9-phenanthryl)propane, however, an intramolecular excimer could not be observed.

Intramolecular Excimers with α, ω-Diarylalkanes

Über vielgliedrige Ringsysteme. I. Die präparativ ergiebige Synthese der Polymethylenketone mit mehr als 6 Ringgliedern

More than twenty examples illustrate the recently developed oxidoketone-alkynone-fragmentation, whereby α,β-epoxy-ketones are cleaved under mild conditions with p-toluenesulfonyl-hydrazine to give acetylenic ketones or aldehydes.

Die Synthese von Acetylen‐carbonyl‐Verbindungen durch Fragmentierung von α, β‐Epoxy‐ketonen mit p‐Toluolsulfonylhydrazin. Vorläufige Mitteilung

Zur Kenntnis des Kohlenstoffringes VI. Über die relative Bildungsleichtigkeit, die relative Beständigkeit und den räumlichen Bau der gesättigten Kohlenstoffringe

W. Brugger

Papers

Zur Kenntnis des Kohlenstoffringes VI. Über die relative Bildungsleichtigkeit, die relative Beständigkeit und den räumlichen Bau der gesättigten Kohlenstoffringe

Zur Kenntnis des Kohlenstoffringes X. Über die monocyclischen Diketone des 16-, 18- und 30-gliedrigen Kohlenstoffringes

About the mining of tetrahydro-irons.