Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

Abstract

Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize polyfunctionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe), and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3-and 2,5-di-substituted thiophenes. Electrophilic aromatic C-H/C-Si bromination on thiophene boronate esters is shown to take place without breaking the C-B bond, and one-pot C-H borylation/Suzuki-Miyaura cross-coupling has been accomplished on 2-and 3-borylated thiophenes.

Synthesis and Photophysical Properties of New α,Ω-Bis(Tpy)Oligothiophenes and Their Metallo-Supramolecular Polymers With Zn2+Ion Couplers

“…The distillation residue was dissolved in hexane and filtered through a small column of silica to obtain the desired product as a yellowish oil (685 mg, 68%). 1 General procedure for synthesis of boronates was adopted from Chotana (28). Hex 2 Th 2 (784 mg, 2.34 mmol) was dissolved in dry hexane (10 mL) under argon atmosphere, dtbpy (30 mg, 0.11 mmol) and [Ir(OMe)(COD)] 2 (22 mg, 0.033 mmol) were added, the mixture was bubbled with argon for 10 minutes and then HBor (1.4 mL, 9.6 mmol) was added.…”

Synthesis and Applications of Group 14-metalated Arylboranes

“…The rhodium-catalysed metathesis of cyano carbon bond in the boronate 47 and the Si Si bond in hexamethyldisilane resulted in silylated phenylboronic ester 48 (Scheme 21) [30,31] Ir-catalyzed borylation of 2-(trimethylsilyl)thiophene 49 with HBPin afforded its 5-boronated derivative 50 whereas in the case of 2-chloro-5-(trimethylsilyl)thiophene 51 the BPin function was placed at the sterically less hindered C-3 to give compound 52 (Scheme 22) [32].…”

Harnessing C–H Borylation/Deborylation for Selective Deuteration, Synthesis of Boronate Esters, and Late Stage Functionalization

“…Namely, certain substrates, such as 2-substituted thiophenes, undergo selective sequential borylations beginning with the most reactive C–H bonds. 16,17 If the deborylation rates mirror borylation rates, then a simple protocol for preparing complementary borylation regioisomers could be developed. 18–20 These possibilities are outlined in Scheme 2.…”