Synthesis, Structures of Benzoxazolyl Iridium(III) Complexes, and Applications on C–C and C–N Bond Formation Reactions under Solvent-Free Conditions: Catalytic Activity Enhanced by Noncoordinating Anion without Silver Effect

Abstract

Several new bisbenzoxazolyl iridium(III) complexes have been synthesized and characterized through X-ray crystallography. These complexes exhibit excellent catalytic activity in C−C and C−N bond formation reactions from the alkylation of amine with amine, amine with alcohol, ketone with alcohol, and alcohol with alcohol through a borrowing hydrogen reaction. Moreover, these iridium(III) complexes are effective catalysts for the alkylation of amine with alcohol and ketone with alcohol under solvent-free conditions. The catalytic activity of these complexes is greatly enhanced by noncoordinating, while the experiments have excluded the possibility of a "silver effect" (bimetallic catalysis or silverassisted metal catalysis) from the experiments.

Retracted: Synthesis of 2‐Arylisoindoline Derivatives Catalyzed by Reusable 1,2,4‐Triazole Iridium on Mesoporous Silica through a Cascade Borrowing Hydrogen Strategy

“…Recently, we synthesized several bis‐benzoxazolyl and ‐benzothienyl iridium(III) complexes that exhibited good catalytic activity in the borrowing hydrogen reaction of simple amines with alcohols, ketones with alcohols, and alcohols with alcohols . However, these complexes and other, common iridium complexes showed no activity in the synthesis of isoindoline derivatives (Scheme ).…”

Alkylation of Amines with Alcohols and Amines by a Single Catalyst under Mild Conditions

“…However, most of the catalysts reported only work for alkylation with alcohols or amines, but not with both. Shvo’s catalyst,7p a [Cp*IrCl 2 (NHC)] complex reported by Peris and co‐workers,7g and a recent example from Li and co‐workers21 are the only catalysts that are able to catalyse both reactions under different reaction conditions or temperatures. Thus, a versatile catalyst capable of promoting alkylation both with alcohols and with amines is desirable.…”

“…The versatility of the system was further examined for the cross‐coupling of amines (Table 4), which is normally carried out at temperatures higher than 150 °C 7g,p–r. 21 Delightfully, the reaction of aniline with diisopropylamine proceeded smoothly under the same mild reaction conditions as those for the alkylation with alcohols. Various para ‐substituted anilines reacted ( 5 a – h ), with all except para ‐acetyl aniline ( 5 f ) affording high yields, with heterocycle or ester groups tolerated ( 5 g and 5 h ).…”

Silver‐Catalyzed Arylation of (Hetero)arenes via Oxidative Benzylic C−C Bond Cleavage of Benzyl Alcohols/ Benzaldehyde

“…Moreover, the discovery of new and innovative bond disconnection strategy, especially for the direct coupling between Csp 2 ‐H and primary commodity chemicals, such as benzyl alcohol, as a counter partner have opened up extensive possibilities. In recent year, several metals (Ir, Ru, Cu, Au) have been studied for C‐alkylation and N‐alkylation reaction but Ag metal is most effective and promising catalysts . In this context, it is highly desirable and challenging to utilize benzyl alcohol (Csp 2 ‐CH 2 OH) as a carboxylic acid surrogate for increasing the efficiency and selectivity of radical‐mediated C−C coupling in a one‐pot tandem catalytic conditions.…”