Manganese-catalyzed dehydrogenative synthesis of urea derivatives and polyureas

A.K. thanks the Leverhulme Trust for an early career fellowship (ECF-2019-161). M.B. wishes to thank the School of Chemistry and EaStCHEM for their support. A.E.O. gratefully acknowledges a fellowship from the Akwa Ibom State University (TETFund).Urea derivatives have significant applications in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents─(di)amines and methanol─via a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earth-abundant metal, manganese, and liberates H2 gas, valuable by itself, as the only byproduct, making the overall process highly atom-economic. A broad variety of symmetrical and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation, suggesting that the reaction proceeds via an isocyanate intermediate.Publisher PDFPeer reviewe

Manganese catalysed dehydrogenative synthesis of polyureas from diformamide and diamines

Authors acknowledge the funding from UKRI Future Leaders Fellowship (MR/W007460/1). M.T. and J.C.T. thank the ERC Consolidator Grant (PROMOFS grant agreement 771575) for funding the research. ABN gratefully acknowledges funding from the EPSRC through grant numbers EP/L017008/1, EP/R023751/1 and EP/T019298/1.We report here the synthesis of polyureas from the dehydrogenative coupling of diamines and diformamides. The reaction is catalysed by a manganese pincer complex and releases H2 gas as the only by-product making the process atom-economic and sustainable. The reported method is greener in comparison to the current state-of-the-art production routes that involve diisocyanate and phosgene feedstock. We also report here the physical, morphological, and mechanical properties of synthesized polyureas. Based on our mechanistic studies, we suggest that the reaction proceeds via isocyanate intermediates formed by the manganese catalysed dehydrogenation of formamides.Publisher PDFPeer reviewe

Manganese Catalysed Dehydrogenative Synthesis of Urea Derivatives and Polyureas

Urea derivatives are prevalent intermediates in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries and have a current annual market of USD 885 million. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents - (di)amines, and methanol via a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earth-abundant metal, manganese, and liberates H2 gas, valuable by itself, as the only by-product making the overall process atom-economic, and sustainable. A broad variety of symmetrical, and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation suggesting that the reaction proceeds via an isocyanate intermediate

Polyureas as SEI-forming Additives for Li Metal Anodes

We report here the first example of the use of an organic “polyurea” polymer as a SEI-forming additive for the lithium metal anode for lithium oxygen batteries. The presence of a suitable polyurea can significantly increase the coulombic efficiency and cycling of the anode in the presence of oxygen in the liquid electrolyte. The findings demonstrate proof of concept for the application of polyureas and other organic polymers for next-generation type batteries with metal anode

Manganese Catalysed Dehydrogenative Synthesis of Polyureas from Diformamide and Diamines

We report here the synthesis of polyureas from the dehydrogenative coupling of diamines and diformamides. The reaction is catalysed by a manganese pincer complex and releases H2 gas as the only by-product making the process atom-economic and sustainable. This work advances the current state-of-the-art by replacing a toxic feedstock – diisocyanates (used to make polyureas) with a safer feedstock – diformamides and using a catalyst based on an earth-abundant metal. We also report here the physical and mechanical properties of the isolated polyureas. We suggest that the reaction proceeds via isocyanate intermediates that are formed by the manganese catalysed dehydrogenation of formamides

British III done: recent work on Shakespeare and British, English, Irish, Scottish and Welsh identities

This contribution to <i>Literature Compass</i> has a three-fold purpose. First, it aims to do what it says in the title, and flag up recent approaches to British identities in Shakespeare studies. Secondly, it seeks to remind readers of an earlier and now largely forgotten tradition of nationalist criticism and scholarship preoccupied with the place of Britain – nation, state and empire – that flourished in the 1920s and 1930s. Thirdly, it endeavours to excavate some of the more obscure material on the subject that, because of its place of publication, may have been overlooked. The material collected here covers issues of borders, colonialism, culture, genre, identity, invasion, language, mapping, monarchy, plantation, union, and the matter of Britain, especially in the histories, though as will be seen this work encompasses most of Shakespeare's corpus. The short introductions to each section and the accompanying bibliography of over 300 items, ranging from notes and queries to substantial essays, is divided into six sections, beginning with a brief overview of the historical debate, then focusing on criticism dealing broadly with Britain, then embracing material ordered by constituent nation: England, Ireland, Scotland and Wales. That there is an even spread of material under this handful of headings suggests that each and every nation within this multi-nation state, as well as the problematic and often contested whole, has attracted its fair share of critical concern