Arslan Burcu, Gülcemal Süleyman
Department of Chemistry, Ege University, 35100 Bornova, Izmir, Turkey.
Dalton Trans. 2021 Feb 9;50(5):1788-1796. doi: 10.1039/d0dt04082g.
A series of backbone-modified N-heterocyclic carbene (NHC) complexes of iridium(i) (1d-f) have been synthesized and characterized. The electronic properties of the NHC ligands have been assessed by comparison of the IR carbonyl stretching frequencies of the in situ prepared [IrCl(CO)2(NHC)] complexes in CH2Cl2. These new complexes (1d-f), together with previously prepared 1a-c, were applied as catalysts for the α-alkylation of arylacetonitriles with an equimolar amount of primary alcohols or 2-aminobenzyl alcohol. The catalytic activities of these complexes could be controlled by modifying the N-substituents and backbone of the NHC ligands. The NHC-IrI complex 1f bearing 4-methoxybenzyl substituents on the N-atoms and 4-methoxyphenyl groups at the 4,5-positions of imidazole exhibited the highest catalytic activity in the α-alkylation of arylacetonitriles with primary alcohols. Various α-alkylated nitriles and aminoquinolines were obtained in high yields through a borrowing hydrogen pathway by using 0.1 mol% 1f and a catalytic amount of KOH (5 mol%) under an air atmosphere within significantly short reaction times.
已合成并表征了一系列铱（I）的主链修饰的N-杂环卡宾（NHC）配合物（1d - f）。通过比较在二氯甲烷中原位制备的[IrCl(CO)2(NHC)]配合物的红外羰基伸缩频率，评估了NHC配体的电子性质。这些新配合物（1d - f）与先前制备的1a - c一起，用作芳基乙腈与等摩尔量的伯醇或2-氨基苄醇进行α-烷基化反应的催化剂。这些配合物的催化活性可通过修饰NHC配体的N-取代基和主链来控制。在咪唑的4,5-位带有4-甲氧基苄基取代基且在N原子上带有4-甲氧基苯基的NHC-IrI配合物1f在芳基乙腈与伯醇的α-烷基化反应中表现出最高的催化活性。在空气气氛下，使用0.1 mol%的1f和催化量的KOH（5 mol%），通过借氢途径在显著短的反应时间内以高产率获得了各种α-烷基化腈和氨基喹啉。
