Cross‐Coupling of Nonactivated Alkyl Halides with Alkynyl Grignard Reagents: A Nickel Pincer Complex as the Catalyst

Abstract

In a pinch: The nickel pincer complex 1 catalyzes the cross‐coupling of the title compounds with remarkable substrate scope and functional group tolerance. A nickel/alkynyl species was isolated and shown to be catalytically competent. THF=tetrahydrofuran, O‐TMEDA=bis[2‐(N,N‐dimethylaminoethyl)] ether.

Mild and Phosphine-Free Iron-Catalyzed Cross-Coupling of Nonactivated Secondary Alkyl Halides with Alkynyl Grignard Reagents

“…[1] Data for 1 H NMR were reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, qu = quintet, sex = sextet, m = multiplet, ovrlp = overlap, br = broad), coupling constants, and integration. All 13 C NMR spectra were reported in ppm relative to CDCl 3 (77.16 ppm) unless otherwise stated, [1] and were obtained with complete 1 H decoupling. All GC analyses were performed on a Perkin-Elmer Clarus 400 GC system with a FID detector.…”

“…The following known starting materials (alkyl halides and terminal alkynes) were prepared according to the literature procedures: [2][3][4][5][6][7][8][9][10][11][12][13] …”

“…= 4.4 : 1) O Me O I 5-iodopentyl acetate [9] N O 4-(hex-5-yn-1-yl)morpholine [10] (ii) Alkynes O O 2-(hept-6-yn-1-yloxy)tetrahydro-2H-pyran [11] N 9-(hex-5-yn-1-yl)-9H-carbazole [12] OMe 1-ethynyl-4-methoxybenzene [13] SMe (4-ethynylphenyl)-(methyl)sulfane [13] O NEt 2 N,N-diethyl-4-ethynylbenzamide [13] 2-ethynyl-5-methylthiophene [13] S Me 3beta-iodo-5-cholestene [5] H H H H I…”

“…new starting materials and substituted alkyne products were characterized by 1 H NMR and 13 C NMR spectroscopies and high-resolution mass spectrometry (HRMS). In case the new compounds could not be detected by HRMS, the compounds ([M]) were then detected by GCMS analysis and their purities were further determined by GC-MS analysis.…”

Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl–Aryl Kumada Coupling Reactions

“…[9][10][11] Our group has developed a nickel(II) pincer complex [( Me N 2 N)Ni-Cl] (1, Nickamine) 12 as a catalyst for the coupling of unactivated alkyl halides with alkyl, aryl, and alkynyl Grignard reagents ( Figure 1). [13][14][15][16][17] The well-defined nature of Nickamine prompted us to study the mechanism of these Kumada coupling reactions. 18,19 Recently, such study led to the discovery of a bimetallic radical oxidative addition mechanism for Ni-catalyzed alkyl-alkyl Kumada coupling.…”