Borverbindungen, 9. Metathetische Ring‐Ring‐Gleichgewichte bei Dioxaboracycloalkanen

Abstract

Aryldihydroxyboranes (2,lO) condense with u,o-alkanediols HO--(CH,),-OH (6), which leads to an equilibrium of oligomeric rings (7) of different size due to a ligand exchange at the boron atom. With low diols (6, x=2,3) the rate of establishing the equilibrium of the exchange reaction is slow enough for isolating the five-and six-membered heterocycles (7, n = 1). Diols with x 2 5, however, lead to the equilibrium mixture of oligomeric heterocycles in a somewhat analogous way to olefin metathesis. EinjiihrungBei der Kondensation von 1,5-Pentandiolen 1 mit Phenyldihydroxyboran (2) entstehen extrem zahe, farblose, nahezu glasartige ole, bei denen es sich nicht um die nach'*2) erwarteten Kettenpolymere 3 handelt. Stattdessen sprechen die 'H NMR-, IR-und massenspektroskopischen Ergebnisse fur die Heterocyclenstruktur 43).

Investigation of Organoboronates in Metathesis Polymerization

“…In any event, the materials resulting immediately from bulk ADMET polymerization range from glassy hard plastics to highly viscous oils, observations which unequivocally indicate that oligomers and/or polymers can be formed. Standard workup conditions lead to depolymerization, most likely via ring formation, a result which is supported by the work of Gerwarth A) via a conventional step-condensation polymerization.…”

“…Standard workup conditions lead to depolymerization, most likely via ring formation, a result which is supported by the work of Gerwarth. 20 His research group attempted to polymerize phenylboronic acid with a series of long-chain diols (Figure 5A) via a conventional step-condensation polymerization. No high molecular weight polymers could be obtained; instead, an equilibrium mixture of cyclic materials was formed due to intermolecular and intramolecular ligand exchange reactions occurring between boronate moieties (Figure 5B).…”

Borverbindungen, 12. Mitteilung Das Kristallisationsverhalten der Poly(2-phenyl-1.3.2-dioxabora-cycloalkane) / Boron Compounds, Part 12 The Crystallizing Behaviour of Poly(2-phenyl-l,3,2-dioxybora-cycloalkanes)

“…Die Darstellung und Reinigung von 4 a, 4b, 4 c und 5 erfolgte nach der beschriebenen Kondensationsmethode und Hoch Vakuumdestillation in einer Spezialapparatur [2,3].…”

“…Die bei der Kondensation erhaltenen rohen Gemische cyclischer Oligomerer 4 zeigen das Destillationsverhalten, wie es für diese Substanzklasse typisch ist[2,3]. Unsaubere Substanzen weisen selbst nach Wochen noch keine Neigung zur Verfestigung auf, während bei hochreinem 4 a die Kristallisation bereits nach einigen Stunden einsetzt und bei ca.…”

Ion Conductive Characteristics of Alkylborane Type and Boric Ester Type Polymer Electrolytes Derived from Mesitylborane

“…Furthermore, dehydrocoupling polymerization 8 between thexylborane and diols was also examined by them to give boric ester main chain polymers at mild reaction conditions. This method is considered to be favorable in comparison with polycondensation between alkanediol and phenylboric acid in which water is generated during the polymerization because of the instability of boric ester toward hydrolysis. In recent studies of Chujo et al, the mesitylboron group, unlike the phenylboron group, stands even under severe reaction conditions without disproportionation of the boric ester monomer to give well-defined polymers such as poly(phenylene borane)s 8 and poly(boric carbamate)s 7 due to the steric hindrance of the mesityl group.…”