Karmel, Caleb published the artcileIridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand, Formula: C13H19BO4S, the publication is Angewandte Chemie, International Edition (2020), 59(15), 6074-6081, database is CAplus and MEDLINE.
The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C-H bonds, were poor in many cases. The authors report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)]2 (cod = 1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C-H bonds of these rings under conditions that the borylation of C-H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.
Angewandte Chemie, International Edition published new progress about 960116-27-2. 960116-27-2 belongs to esters-buliding-blocks, auxiliary class Thiophene,Boronic acid and ester,Ester,Thiophene,Boronate Esters,Boronic Acids,Boronic acid and ester,, name is Ethyl 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene-3-carboxylate, and the molecular formula is C13H19BO4S, Formula: C13H19BO4S.
Referemce:
https://en.wikipedia.org/wiki/Ester,
Ester – an overview | ScienceDirect Topics