Photopolymerization of Cationic Monomers and Acrylate/Divinylether Blends under Visible Light Using Pyrromethene Dyes

New photoinitiating systems based on boron-dipyrromethene dye (bodipy)/iodonium salt and optionally tris­(trimethylsilyl)­silane are proposed for the polymerization of divinylether and epoxy monomers upon visible-light exposure. The presence of the silane increases the epoxide rate of polymerization and conversion. Using acrylate/vinyl ether blends, the synthesis of cross-linked polymer networks (possessing two <i>T</i>_g values: −11 and 111 °C) is also successfully achieved through concomitant cationic and radical polymerization pathways. The chemical mechanisms associated with these initiating systems are investigated by steady-state photolysis and ESR experiments

Soft Photopolymerizations Initiated by Dye-Sensitized Formation of NHC-Boryl Radicals under Visible Light

A procedure for the production of N-heterocyclic carbene–boryl radicals (NHC-BH₂^•) upon visible light irradiation under soft conditions is presented. New acridine orange (dye)/diphenyl disulfide/NHC–BH₃ and dye/sulfonium salt/NHC–BH₃ three-component initiating systems are introduced for the efficient visible light photopolymerization of trimethylolpropane triacrylate. The new systems could be extendend to polymerization reactions in water (hydroxyethyl acrylate and hydroxyethyl methyl acrylate), which proceeded with strongly improved polydispersity. The chemical mechanisms are investigated through EPR and photolysis experiments

Mechanistic and Preparative Studies of Radical Chain Homolytic Substitution Reactions of N‑Heterocyclic Carbene Boranes and Disulfides

Reactions of 1,3-dimethylimidazol-2-ylidene–borane (diMe-Imd-BH₃) and related NHC–boranes with diaryl and diheteroaryl disulfides provide diverse NHC–boryl monosulfides (diMe-Imd-BH₂SAr) and NHC–boryl disulfides (diMe-Imd-BH­(SAr)₂). Heating in the dark with 1 equiv of disulfide favors monosulfide formation, while irradiation with 2 equiv disulfide favors disulfide formation. With heteroaryl disulfides, the NHC–borane in the primary NHC–boryl sulfide product migrates from sulfur to nitrogen to give new products with a thioamide substructure. Most substitution reactions are thought to proceed through radical chains in which homolytic substitution of a disulfide by an NHC–boryl radical is a key step. However, with electrophilic disulfides under dark conditions, a competing ionic path may also be possible

Mechanistic and Preparative Studies of Radical Chain Homolytic Substitution Reactions of N‑Heterocyclic Carbene Boranes and Disulfides

Reactions of 1,3-dimethylimidazol-2-ylidene–borane (diMe-Imd-BH₃) and related NHC–boranes with diaryl and diheteroaryl disulfides provide diverse NHC–boryl monosulfides (diMe-Imd-BH₂SAr) and NHC–boryl disulfides (diMe-Imd-BH­(SAr)₂). Heating in the dark with 1 equiv of disulfide favors monosulfide formation, while irradiation with 2 equiv disulfide favors disulfide formation. With heteroaryl disulfides, the NHC–borane in the primary NHC–boryl sulfide product migrates from sulfur to nitrogen to give new products with a thioamide substructure. Most substitution reactions are thought to proceed through radical chains in which homolytic substitution of a disulfide by an NHC–boryl radical is a key step. However, with electrophilic disulfides under dark conditions, a competing ionic path may also be possible

Mechanistic and Preparative Studies of Radical Chain Homolytic Substitution Reactions of N‑Heterocyclic Carbene Boranes and Disulfides

Reactions of 1,3-dimethylimidazol-2-ylidene–borane (diMe-Imd-BH₃) and related NHC–boranes with diaryl and diheteroaryl disulfides provide diverse NHC–boryl monosulfides (diMe-Imd-BH₂SAr) and NHC–boryl disulfides (diMe-Imd-BH­(SAr)₂). Heating in the dark with 1 equiv of disulfide favors monosulfide formation, while irradiation with 2 equiv disulfide favors disulfide formation. With heteroaryl disulfides, the NHC–borane in the primary NHC–boryl sulfide product migrates from sulfur to nitrogen to give new products with a thioamide substructure. Most substitution reactions are thought to proceed through radical chains in which homolytic substitution of a disulfide by an NHC–boryl radical is a key step. However, with electrophilic disulfides under dark conditions, a competing ionic path may also be possible

Mechanistic and Preparative Studies of Radical Chain Homolytic Substitution Reactions of N‑Heterocyclic Carbene Boranes and Disulfides

Reactions of 1,3-dimethylimidazol-2-ylidene–borane (diMe-Imd-BH₃) and related NHC–boranes with diaryl and diheteroaryl disulfides provide diverse NHC–boryl monosulfides (diMe-Imd-BH₂SAr) and NHC–boryl disulfides (diMe-Imd-BH­(SAr)₂). Heating in the dark with 1 equiv of disulfide favors monosulfide formation, while irradiation with 2 equiv disulfide favors disulfide formation. With heteroaryl disulfides, the NHC–borane in the primary NHC–boryl sulfide product migrates from sulfur to nitrogen to give new products with a thioamide substructure. Most substitution reactions are thought to proceed through radical chains in which homolytic substitution of a disulfide by an NHC–boryl radical is a key step. However, with electrophilic disulfides under dark conditions, a competing ionic path may also be possible