Theoretical and Experimental Studies on Elementary Reactions in Living Radical Polymerization via Organic Amine Catalysis

The reaction mechanism of living radical polymerization using organic catalysts, a reversible complexation mediated polymerization (RCMP), was studied using both theoretical calculations and experiments. The studied catalysts are tetramethyl­guanidine (TMG), triethyl­amine (TEA), and thiophene. Methyl 2-iodoisobutyrate (MMA-I) was used as the low-molar-mass model of the dormant species (alkyl iodide) of poly­(methyl methacrylate) iodide (PMMA-I). For the reaction of MMA-I with TEA to generate MMA^• and ^•I-TEA radicals (activation process), the Gibbs activation free energy for the inner-sphere electron transfer mechanism was calculated to be 39.7 kcal mol^–1, while the observed one was 25.1 kcal mol^–1. This difference of the energies suggests that the present RCMP proceeds via the outer-sphere electron transfer mechanism, i.e., single-electron transfer (SET) reaction from TEA to MMA-I to generate MMA^• and ^•I-TEA radicals. The mechanism of the deactivation process of MMA^• to generate MMA-I was also theoretically studied. For the studied three catalysts, the theoretical results reasonably elucidated the experimentally observed polymerization behaviors

Two-Step Synthesis of Difluoromethyl-Substituted 2,3‑Dihydrobenzoheteroles

3-Difluoromethylated 2,3-dihydrobenzo­heteroles, 2,3-dihydro­benzo­furans, 2,3-dihydro­benzo­thio­phenes, and indolines were readily synthesized from <i>ortho</i>-heterosubstituted bromobenzenes, 2-bromophenols, 2-bromo­benzene­thiols, and 2-bromo­anilines, respectively, in two steps: (1) γ-selective allylic substitution of 3-bromo-3,3-difluoro­propene with heteronucleophiles and (2) intramolecular radical cyclization of the resulting 3,3-difluoroallylic compounds

Palladium-Catalyzed [4 + 2] Cycloaddition of Aldimines and 1,4-Dipolar Equivalents via Amphiphilic Allylation

The combination of Pd catalyst and diethylzinc with triethylborane promotes the amphiphilic allylation of aldimines with 2,3-bismethylenebutane-1,4-diol derivatives to serve as bis-allylic zwitterion species to form 3,4-bismethylenepiperidines via a formal [4 + 2] cycloaddition reaction. 3,4-Bismethylenepiperidine rings are applicable for the synthesis of isoquinoline derivatives via the Diels–Alder reaction followed by an oxidation reaction with DDQ

Platform for Ring-Fluorinated Benzoheterole Derivatives: Palladium-Catalyzed Regioselective 1,1-Difluoroallylation and Heck Cyclization

The synthesis of difluoromethylene-containing heterocycles was achieved via the palladium-catalyzed 1,1-difluoroallylation of heteronucleophiles followed by intramolecular Heck reaction. The allylic substitution of 3-bromo-3,3-difluoropropene was regioselectively accomplished by heteronucleophiles without rearrangement to give the corresponding 1,1-difluoroallylated compounds whose Heck cyclization proceeded in a 5-<i>exo</i> manner to afford ring-difluorinated indolines and dihydrobenzofurans. Their defluorinative allylic substitution further provided 2-fluoroindoles and 2-fluorobenzofurans