Thermodynamic, kinetic, and mechanistic studies of the thermal guanidine metathesis reaction

Abstract

The key structural features that dictate the thermodynamics and kinetics of the thermal guanidine metathesis reaction are presented. A potential mechanism for the transformation is also discussed.

Postpolymerization Modification by Nucleophilic Addition to Styrenic Carbodiimides

“…Relaxation times of dm-CAN 5 were faster at all temperatures than that of CAN 5 : for example, τ* of dm-CAN 5 at 170 °C (∼1650 s) was approximately 65% that of CAN 5 at the same temperature (∼2537 s; Figure d). This is consistent with the effects of sterics on TGM reaction kinetics, as more sterically congested guanidines undergo more rapid exchange . The more highly cross-linked CAN 10 also possessed shorter τ* (∼1150 s at 170 °C) compared to CAN 5 at all temperatures.…”

“…Accordingly, the plateau modulus of the more highly cross-linked CAN 10 (2.2 MPa at 170 °C) was greater than either CAN 5 variant. Despite the dissociative nature of the TGM reaction, no significant drop in E ′ was observed at higher temperatures. This is consistent with dissociative CAN systems in which K eq greatly favors cross-link association at all experimental temperatures. , Reprocessing experiments in which a sample of CAN 5 was reground and subjected to melt pressing indicated that the material could be recycled multiple times, although some variation in E ′ and T g was observed with each cycle (Figures c and S39 and Table S2).…”

“…Additionally, recent work demonstrated the preparation and modification of a new class of polymeric CDIs by Ir-catalyzed ring-opening metathesis polymerization . Aryl-substituted CDIs in particular occupy a useful niche of reactivity: they are bench-stable over the span of years, but react rapidly and quantitatively with primary or secondary alkyl amines under ambient conditions . While they have been explored as substrates for SmI 2 -mediated reductive coupling reactions, we envisioned styrenic aryl CDIs as a broadly useful PPM platform amenable to preparation by traditional radical polymerization methods.…”

“… 23 Aryl-substituted CDIs in particular occupy a useful niche of reactivity: 24 they are bench-stable over the span of years, but react rapidly and quantitatively with primary or secondary alkyl amines under ambient conditions. 25 While they have been explored as substrates for SmI 2 -mediated reductive coupling reactions, 26 we envisioned styrenic aryl CDIs as a broadly useful PPM platform amenable to preparation by traditional radical polymerization methods. Here we present the free and controlled radical (co)polymerization of styrenic CDIs and their modification with alkyl amines.…”

Carbodiimide and Isocyanate Hydroboration by a Cyclic Carbodiphosphorane Catalyst**

“…The authors have cited additional references within the Supporting Information. [99][100][101][102][103][104][105] the Arnold and Mabel Beckman Foundation through the Beckman Scholars Program.…”