NHC/Nickel(II)‐Catalyzed [3+2] Cross‐Dimerization of Unactivated Olefins and Methylenecyclopropanes

Abstract

Cross‐dimerization of a methylenecyclopropane (1) and an unactivated alkene (2) with typical hydroalkenylation reactivity was observed for the first time by using a [NHC‐Ni(allyl)]BArF catalyst (NHC=N‐heterocyclic carbene). Results show that the C−C cleavage of 1 did not involve a Ni0 oxidative addition, which was crucial in former systems. Thus the method reported here emerges as a complementary method for attaining highly chemo‐ and regioselective synthesis of methylenecyclopentanes (3) with broad scope. An efficient NHC/NiII‐catalyzed rearrangement of 1 leads to the convergent synthesis of 3 in the presence of 2.

Acenaphthene-Based N-Heterocyclic Carbene Metal Complexes: Synthesis and Application in Catalysis

“…It should be mentioned that no clear influence of NHC ligand on selectivity (crossdimerization vs. homodimerization or oligomerization) could be provided. Similar conclusions could be drawn for Ni-catalyzed [3+2] cross-dimerization of methylene cyclopropanes with alkynes, developed by Ho and co-workers (Scheme 54) [81]. Among NHC ligands selected in the initial optimization, the authors reported a higher yield for more electron-rich ligands (IPr Cl 123b vs. IPr 123a).…”

“…The reaction afforded tertiary amines in varying yields, depending on the base and solvent used (Scheme 29). The last example of an achiral transformation, proving the usefulness of NHC nickel complexes for [3+2] cross-dimerization, was developed by Huang and Ho in 2020 [81]. The authors described the unique reactivity of unactivated olefins 67 and methylenecyclopropanes 66, leading to cyclopentanes bearing exocyclic double bonds (Scheme 30).…”

BIAN‐NHC Ligands in Transition‐Metal‐Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N‐Heterocyclic Carbenes?

“…In 2020, Ho and co‐workers reported a highly selective cross‐dimerization of olefins and methylenecyclopropanes catalyzed by Ni‐BIAN‐NHC complexes (Scheme 27). [63] The authors found that a combination of [Ni(BIAN‐IPr)(allyl)Cl] catalyst 22 and NaBAr F could be used to achieve high yields and remarkable selectivity in this [3+2] cross‐dimerization. The use of BIAN‐IPr ligand provided significantly better results than the classical imidazolylidene‐based IPr and imidazolinylidene‐based SIPr ligands , while the closest, yet lower, reactivity was observed with the difficult to prepare IPent Me ligand.…”

(NHC)Ni(II)-Directed Insertions and Higher Substituted Olefin Synthesis from Simple Olefins

“…To our delight, a cross-[3 + 2]-dimerization of methylenecyclopropane (MCP) with an olefin was developed using a bulky [(NHC)Ni(allyl)Cl]/NaBAr F catalyst (Figure 21A). 4 Without the β-H elimination/transfer pathway after the MCP rearrangement, highly chemo-and regioselective carbonickelation can be done at ambient temperature with a vast substrate scope, including various linear and cyclic alkenes and dienes. In the olefin donor insertion step, Markovnikov selectivity is generally favored, which is consistent with the preference noted in the cross-HA when a bulky NHC is used.…”

“…Hence, with the above outlook in mind, the potentials of the (NHC)­Ni­(II) catalyst in developing other challenging organic transformations that require a selective insertion step were explored. To our delight, a cross-[3 + 2]-dimerization of methylenecyclopropane (MCP) with an olefin was developed using a bulky [(NHC)­Ni­(allyl)­Cl]/NaBAr F catalyst (Figure A) . Without the β-H elimination/transfer pathway after the MCP rearrangement, highly chemo- and regioselective carbonickelation can be done at ambient temperature with a vast substrate scope, including various linear and cyclic alkenes and dienes.…”