Pentacoordinated Carboxylate π‐Allyl Nickel Complexes as Key Intermediates for the Ni‐Catalyzed Direct Amination of Allylic Alcohols

Abstract

Direct amination of allylic alcohols with primary and secondary amines catalyzed by a system made of [Ni(1,5-cyclooctadiene)2 ] and 1,1'-bis(diphenylphosphino)ferrocene was effectively enhanced by adding nBu4 NOAc and molecular sieves, affording the corresponding allyl amines in high yield with high monoallylation selectivity for primary amines and high regioselectivity for monosubstituted allylic alcohols. Such remarkable additive effects of nBu4 NOAc were elucidated by isolating and characterizing some nickel complexes, manifesting the key role of a charge neutral pentacoordinated η(3) -allyl acetate complex in the present system, in contrast to usual cationic tetracoordinated complexes earlier reported in allylic substitution reactions.

The Importance of Ligand‐Induced Backdonation in the Stabilization of Square Planar d10 Nickel π‐Complexes

“…For example, we are exploring the organometallicc hemistry of nickel, [10][11][12][13][14] which has undergone ar enaissance in recent years. [15][16][17][18][19][20][21] Our focus has been the structure and reactivityo fn ickel p-complexes, which have been reported in aw ide range of catalytic processes, including the coupling of CO 2 and ethylene, [5,[22][23][24][25][26][27][28][29][30][31][32] intermolecular Tischenkoc oupling, [33][34][35] benzoxasilole synthesis, [36,37] the aldol reaction, [38] allylic alkylation, [39] allylic amination, [40] allylic amidation, [41] epoxide functionalization, [42] and Suzuki-Miyaura coupling. [43] Nickel p-complexes of heteroarenes have also been identified as key intermediates in nickel-catalysed catalystt ransfer polycondensation to form polythiophenes.…”

Catalytic C−C Bond Formation Using a Simple Nickel Precatalyst System: Base‐ and Activator‐Free Direct C‐Allylation by Alcohols and Amines

“…[a] Estimated from 1 H NMR of crude product; [b] Isolated yield; [c] Monoallylated : diallylated (determined from 1 H NMR of crude product); [d] Yield based on recovered starting material; [e] 5 mol % AcOH present; [f] 5 mol % NH 4 OAc present; [g] 5 mol % NBu 4 OAc present; [h] 2 equiv. malonate used.…”

“…[%] [a] Yield [%] [b] Selectivity [c] 1d ppbDMF 80 18 28 50 [d] [14] present;[ h] 2equiv. malonate used.…”

Diphenylphosphine‐Oxide‐Fused and Diphenylphosphine‐Fused Porphyrins: Synthesis, Tunable Electronic Properties, and Formation of Cofacial Dimers

“…Ni II porphyrin 8 showedaroughly planar but waved p-conjugated structure consisting of ar uffled porphyrin core and ap yramidal P=O moiety with am ean plane deviation (MPD) of 0.28 . [9] As another characteristic structuralf eature of the high-spinN i II porphyrin, the NiÀNb onds of 9 are in the range of 2.026-2.038 ,w hich are distinctly longer than those of 8 (1.921-1.931 ). Ni II porphyrin 9 also displayed ap lanar structure with as maller MPD value of 0.20 but formedacovalently linked face-toface dimer with an interplanar distance of 3.57 ,w here the embedded P III atom coordinated to the Ni II atom in ac omplementarym anner.T he observed NiÀPb ondl ength was 2.35 , being similart ot hat of the reportedN i II complex of as imilar five-coordinated squarep yramidal structure.…”