IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) represents the most important NHC (NHC = N-heterocyclic carbene) ligand throughout the field of homogeneous catalysis. Herein, we report the synthesis, catalytic activity, and full structural and electronic characterization of novel, sterically-bulky, easily-accessible NHC ligands based on the hash peralkylation concept, including IPr#, Np# and BIAN-IPr#. The new ligands have been commercialized in collaboration with Millipore Sigma: IPr#HCl, 915653; Np#HCl; 915912; BIAN-IPr#HCl, 916420, enabling broad access of the academic and industrial researchers to new ligands for reaction optimization and screening. In particular, the synthesis of IPr# hinges upon cost-effective, modular alkylation of aniline, an industrial chemical that is available in bulk. The generality of this approach in ligand design is demonstrated through facile synthesis of BIAN-IPr# and Np#, two ligands that differ in steric properties and N-wingtip arrangement. The broad activity in various cross-coupling reactions in an array of N–C, O–C, C–Cl, C–Br, C–S and C–H bond cross-couplings is demonstrated. The evaluation of steric, electron-donating and π-accepting properties as well as coordination chemistry to Au(I), Rh(I) and Pd(II) is presented. Given the tremendous importance of NHC ligands in homogenous catalysis, we expect that this new class of NHCs will find rapid and widespread application.

中文翻译：

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IPr# – 高度受阻、广泛适用的 N-杂环卡宾

IPr（IPr = 1,3-双（2,6-二异丙基苯基）咪唑-2-亚基）代表了整个均相催化领域最重要的 NHC（NHC = N-杂环卡宾）配体。在此，我们报告了基于散列全烷基化概念（包括 IPr#、Np# 和 BIAN-IPr#）的新型、空间庞大、易于获得的 NHC 配体的合成、催化活性以及完整的结构和电子表征。新配体已与 Millipore Sigma 合作商业化：IPr#HCl，915653；Np#HCl; 915912；BIAN-IPr#HCl, 916420，使学术和工业研究人员能够广泛接触用于反应优化和筛选的新配体。特别是，IPr# 的合成取决于苯胺的成本效益、模块化烷基化，苯胺是一种可批量获得的工业化学品。这种方法在配体设计中的通用性通过 BIAN-IPr# 和 Np# 的轻松合成得到证明，这两种配体在空间性质和 N 翼尖排列方面不同。证明了一系列 N-C、O-C、C-Cl、C-Br、C-S 和 C-H 键交叉偶联中各种交叉偶联反应的广泛活性。空间位阻，给电子和接受π的性质以及与Au（I )、Rh( I ) 和 Pd( II )。鉴于 NHC 配体在均相催化中的巨大重要性，我们预计这类新型 NHC 将得到快速和广泛的应用。