Living Metathesis and Metallotropy Polymerization Gives Conjugated Polyenynes from Multialkynes: How to Design Sequence-Specific Cascades for Polymers

Abstract

On the basis of a combined experimental and computational study, a novel method for preparing fully conjugated polyenynes via cascade metathesis and metallotropy (M&M) polymerization of various multialkynes is developed. DFT calculations elucidate the detailed mechanism of the metallotropic 1,3-shift, which is a key process of M&M polymerization. An α,β-(C,C,C)-agostic interaction stabilizing the metallacyclobutadiene transition state is found to be critically important for the successful polymerization with excellent specificity. The polymerization efficiency displayed by the tetrayne monomer is controlled by the steric demands of its substituents, and more complex hexayne monomers can be successfully polymerized to give access to highly conjugated polyenynes via a series of intramolecular metathesis and metallotropic shift cascade reactions. Furthermore, living polymerization led to the synthesis of block copolymers consisting of fully conjugated polyenyne backbones. The implementation of pentayne monomers provides polyenynes with successive C–C triple bonds via consecutive metallotropic 1,3-shift. In short, the design of multialkynes enables the preparation of diverse conjugated polyenyne motifs via selective M&M cascade reactions.

Transient-axial-chirality controlled asymmetric rhodium-carbene C(sp2)-H functionalization for the synthesis of chiral fluorenes

“…We could not locate the corresponding intramolecular cyclopropenation transition state from IN2, and this can be understood by considering that such reaction would generate a fused cyclopropene with high ring strain. Intermediate IN3 is subsequently converted to a more stable Rh-carbene complex IN4 via Rh-1,3shift 69 . Our calculations indicated that this step involves an intersystem crossing (ISC) process via MECP-1 to give the triplet species, 3 IN3, which then undergoes 1,3-Rh migration via a triplet-transition state 3 TS3, finally giving the closed-shell singlet Rh-carbene complex IN4.…”

Highly Sensitive Polydiacetylene Ensembles for Biosensing and Bioimaging

“…In 1993, Charych et al reported the first case of modified PDAs for detection of virus (Charych et al, 1993). During the following 20 years, many PDA-based bioprobes have been developed to detect biomarkers, biomolecules, metal ions, drugs, proteins, nucleic acids, lipids, virus, bacterial, and use to bioimaging (Chae et al, 2016;Park et al, 2016b;Qu et al, 2016;Yamamoto et al, 2016;Jiang et al, 2017;Cui et al, 2018a;Kang et al, 2018; FIGURE 1 | Topochemical photopolymerization of diacetylene. Reprinted with permission from Reppy and Pindzola (2007).…”

Selective Ring-Opening Allene Metathesis: Polymerization or Ruthenium Vinylidene Formation

“…This is in part due to the benchtop stability and high functional group tolerance of Grubbs catalyst. With the emergence of alternative metathesis polymerizations such as cyclopolymerizations, metallotropy, − and enyne metathesis polymerizations, , its surprising that the polymerization of allenes, which are known to be reactive with Grubbs catalyst, remain unexplored. , …”