Regioregular Synthesis of Azaborine Oligomers and a Polymer with a syn Conformation Stabilized by NH⋅⋅⋅π Interactions

Abstract

The regioregular synthesis of the first azaborine oligomers and ac orresponding conjugated polymer was accomplished by Suzuki-Miyaura coupling methods.A n almost perfectly coplanar syn arrangement of the heterocycles was deduced from an X-ray crystal structure of the dimer, which also suggested that N À H···p interactions play an important role.C omputational studies further supported these experimental observations and indicated that the electronic structure of the longer azaborine oligomers and polymer resembles that of poly(cyclohexadiene) more than poly(pphenylene). Ac omparison of the absorption and emission properties of the polymer with those of the oligomers revealed dramatic bathochromic shifts upon chain elongation, thus suggesting highly effective extension of conjugation.

Rhodium‐Mediated Stoichiometric Synthesis of Mono‐, Bi‐, and Bis‐1,2‐Azaborinines: 1‐Rhoda‐3,2‐azaboroles as Reactive Precursors

“…We have identified similar atropisomers for a closely related derivative containing 1,4‐ instead of 1,2‐azaborinine units [8b] . By contrast, the linear 1,2‐azaborinine trimer reported by the groups of Liu and Jäkle preferentially adopts a syn disposition due to favorable N−H⋅⋅⋅π interactions [15] . The presence of a similar interaction in a diphenylacetylene analogue also favored the syn arrangement of the 1,2‐azaborinine groups [17] …”

“…The ring bond distances, which are displayed in Figure 2, display no unusual features. Oligomers of 1,2‐azaborinines have been reported by the group of Liu and Jäkle [15] . Thereby, through Suzuki‐Miyaura cross‐coupling, monomeric 1,2‐azaborinine units were joined together via their 3 and 6 positions, affording dimers, trimers and even a polymer.…”

Poly(arylene iminoborane)s, Analogues of Poly(arylene vinylene) with a BN‐Doped Backbone: A Comprehensive Study

“…In fact, its electronic structure resembles more closely that of poly(cyclohexadiene) or trans‐ cisoid poly(acetylene) (PA) than that of PPP. This behavior was partly ascribed to the limited contribution of the B=N units to the frontier orbitals compared to the C atoms along the chain in PPP and BN‐PPP [11] . Reports on several further exciting examples of polymers comprising 1,2‐azaborinine as part of a polycyclic structural element followed subsequently [12] .…”

The Introduction of the Radical Cascade Reaction into Polymer Chemistry: A One-Step Strategy for Synchronized Polymerization and Modification

“…Only highly efficient and selective organic reactions are suitable to be introduced into polymer chemistry to develop new polymerization methodology. For example, atom transfer radical addition reaction (Wang and Matyjaszewski, 1995;Pintauer and Matyjaszewski, 2008), radical addition-fragmentation reaction (Moad et al, 2008;Chiefari et al, 1998), olefin metathesis reaction (Vougioukalakis and Grubbs, 2010;Grubbs, 2000, 2007), Suzuki coupling reaction (Miyaura et al, 1981;Littke et al, 2000;Kotha et al, 2002;Schluter, 2001;Yokoyama et al, 2007;Baggett et al, 2015), Michael addition reaction (Liu et al, 2003;Wang et al, 2005), Stille coupling reaction (Bao et al, 1995;Littke and Fu, 1999;Yin et al, 2016;Guo et al, 2014), click chemistry reactions (He et al, 2016(He et al, , 2017, multiple components reactions (Deng et al, 2012(Deng et al, , 2016Kreye et al, 2011;Wei et al, 2017;Wu et al, 2017;Xue et al, 2016), Barbier reaction (Sun et al, 2017;Jing et al, 2019) etc. have been successfully introduced into polymer chemistry to develop desired polymerization methodologies (Tebben and Studer, 2011;Jiang et al, 2018;Huang et al, 2019;Liu et al, 1999).…”