Air- and Water-Stable Catalysts for Hydroamination/Cyclization. Synthesis and Application of CCC−NHC Pincer Complexes of Rh and Ir

Abstract

The scope of CCC-NHC pincer complex synthetic methodology by metalation/transmetalation has been extended to Ir. Structural characterization revealed that it is isomorphous with the Rh complex. Both Rh and Ir complexes are efficient catalysts for the hydroamination/cyclization of secondary amines in the presence of air and/or water.

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…This important contribution neither discloses intermolecular hydroamination nor addresses stereoselective versions of this transformation. Hollis [266] has directly compared Rh-and Ir-CCC-NHC pincer complexes (54) for application in cyclohydroamination of secondary aminoalkenes (Scheme 15.65). The Ir complex (54a) yielded slightly improved results, although high reaction temperatures (110 • C) and substrate scope limitations (for example, neither of these catalysts can mediate hydroamination with primary aminoalkenes and substituents…”

“…Interestingly, catalyst performance was not dramatically affected by solvent or by the presence of air and moisture [266]. In contrast to the aforementioned prepared Rh-and Ir-pincer complexes, Stradiotto [267] has disclosed the commercially available [Ir(COD)Cl] 2 for mediating cyclohydroamination of substituted secondary aminoalkenes in typically <24 h at 110 • C (Scheme 15.66).…”

Research Progress in Non-noble Metals Catalyzed Hydroamination of Alkyenes and Alkynes

“…若两基团处于反位(trans), 则必须经过异构化 成顺式后, 才能进一步发生还原消除. 由于该机理第一 步为金属的氧化插入, 金属的化合价增加 2, 因此能以 该机理进行的氢胺化反应, 使用的催化剂必须具有能提 升 2 个化合价的能力, 已报道的主要为靶、铂、钌、铑、 铱等贵金属 [117] . [127] .…”

Synthesis of Saturated Heterocycles via Metal-Catalyzed Alkene Hydroamination or Hydroalkoxylation Reactions

“…Rhodium catalysts described in this section demonstrate high reactivity across a broad range of basic aminoalkene substrates and reports of new rhodium catalysts for hydroaminations of unactivated alkenes continue to emerge (Scheme 27) [50][51][52].…”