Electronic Supplementary Material (ESI) for ChemComm. This journal is © The Royal Society of Chemistry 2017 Supplementary Information N-Heterocycle Carbene Copper Catalyzed Direct Alkylation of Terminal Alkynes with Nonactivated Alkyl Triflates Liqun Jin,*ab Wangfang Hao,a Jianeng Xu,a Nan Sun,a Baoxiang Hu,a Zhenlu Shen,a Weimin Mo,a and Xinquan Hu*ab a College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032, P.R. China b State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical Physics Chinese Academy of Sciences, Lanzhou 730000, P.R. China 1 Table of Contents 1. General 2. General procedure for Cu-catalyzed alkylations of terminal alkynes 3. Reaction optimization of NHC-Copper catalyzed coupling of phenylacetylene with octyl triflate 3. Mechanistic studies 4. Scale-up reactions 5. NMR spectra of copper complexes and coupling products 6. References 2 1. General All reactions were carried out under nitrogen atmosphere unless otherwise noted. All 1H and 13C NMR spectra were recorded on Bruker ADVANCE III 500 MHz spectrometer in deuterium solvents with tetramethylsilane (TMS) as internal standard. NMR multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, q = quartet, sept = septet, m = multiplet, br = broad signal. Chemical shifts are given in ppm and are referenced to TMS (1H, 13C). All spectra were obtained at 25 °C in the solvent indicated. Coupling constants J are given in Hz. GC analyses were performed on Agilent 6890 instrument with FID detector using an HP-5 capillary column (30 m x 0.32 mm (i.d.), 0.25 ). High-resolution mass spectra were recorded in the EI mode on Waters GCT Premier TOF MS. Reactions rates were acquired by Mettler-Toledo ReactIR™15 with iC IR software. Melting points were determined on BUCHI M-565 apparatus. Single crystal X-ray diffraction data were collected on a Bruker Apex II CCD detector using Mo-Kradiation ( = 0.71073 Å). Flash column chromatography was performed on neutral silica gel (200-300 mesh) with ethyl acetate/petroleum ether as eluent. All solvents were used after dried and distillation. N-heterocycle carbene copper chlorides (NHCCuCl) were synthesized according to the reported methods.1 All bases were commercial available and used directly. Most terminal alkynes were commercial available and used directly. Alkyne 1e was prepared through Pd-catalyzed coupling between 2,6-dibromobenzene and 2-methyl-3-butyn-2-ol, followed by the basic cleavage of the protecting group.2 1p,3 1q,3 and 1j4 were prepared through Pd- catalyzed coupling of the corresponding aryl bromide and (trimethylsilyl)acetylene and following desilylations.5 5f was synthesized starting from phenol and 5- chloropentyne.6 Alkyl sulfonate esters were synthesized from the corresponding alcohols according to the literature procedures.7 2. General procedure for Cu-catalyzed alkylations of terminal alkynes 3 The Young tube was charged with IMesCuCl (20.2 mg, 5 mol%), t-AmONa (165 mg, 1.5 mmol) and CH2Cl2 (3 mL). Then, terminal alkyne (1 mmol) and alkyl triflates (1.5 mmol) were added. After stirring the resultant mixture at 40 oC for 12 h, the solvent was removed in vacuo and the desired product was isolated by column chromatography. For aliphatic alkynes, the reactions were conducted as the similar procedure with 10 mol% of IMesCuCl as the catalyst. 3. Reaction optimization of NHC-Copper catalyzed coupling of phenylacetylene with octyl triflate [Cu] n n Ph + C H OTf Ph C8H17 8 17 o 1a 2a K2CO3, DCM, 40 C 3a Entry [Cu] Base Solvent Yield (%)b 1 SIPrCuCl K2CO3 toluene 36 2 SIPrCuCl K2CO3 hexane 27 DMF 2 3 SIPrCuCl K2CO3 4 SIPrCuCl K2CO3 THF 14 5 SIPrCuCl Cs2CO3 DCM 27 6 SIPrCuCl NaHCO3 DCM 0 7 SIPrCuCl Et3N DCM 0 8 SIPrCuCl t-BuONa DCM 51 9 SIPrCuCl t-AmONa DCM 76 10 IPrCuCl t-AmONa DCM 79 11 SIMesCuCl t-AmONa DCM 71 12 IMesCuCl t-AmONa DCM 84(76c) 13 CuI t-AmONa DCM 60 14 CuCl t-AmONa DCM 38 15 no [Cu] t-AmONa DCM 17 a Reaction conditions: 1a (0.3 mmol), 2a (0.45 mmol), catalyst (5 mol%), base (0.45 mmol), solvent (1 mL), 12 h. b Yield was determined by GC using biphenyl as an internal standard. c Isolated yield in the parenthesis. 4 Initial screening of the solvents suggested that changing dichloromethane to others, like toluene or hexane, slightly lowered the yields of the target product (entry 1 and 2). When using DMF and THF, the yield dropped substantially (entry 3 and 4). Then, in dichloromethane, changing the base to a stronger one, such as tBuONa, increased the yield of the cross-coupling product 3a to 51% (entry 8). To our delight, using tAmONa instead led to the desired product 3a in up to 76% yield (entry 9), presumably due to the better solubility of tAmONa in dichloromethane. Unfortunately, exploring other bases gave clear detrimental effects (entries 5-7). On switching to other NHC ligands, IPr and SIMes had only marginal effects on the reaction (entry 10 and 11). Notably, IMes clearly proved to be superior with a good GC yield of 84% and 76% isolated (entry 12). Other generally used cuprous salts CuI and CuCl were also tested, which delivering lower yield to 60% and 38%, respectively (entry 13 and 14). Meanwhile, a control experiment without the addition of copper was remarkably inhibited (entry 15) 4. Mechanistic studies t-AmONa, toluene IMesCuCl + Ph [ IMes Cu Ph]n Eq. 1 o 40 C, 3 h complex I Isolated yield: 80% 4.1 Procedure for the reaction of phenyl acetylene and IMesCuCl To a Schlenk tube, IMesCuCl (468.2 mg, 1.0 mmol), t-AmONa (111.2 mg, 1.0 mmol), phenyl acetylene (99.0 mg, 0.97 mmol) and toluene (5 mL) were added. The mixture was then heated at 40 oC for 3 h. After filtration and 3 mL of toluene wash of the filter twice, the filtrate was concentrated. Wash the crude product with hexane for three times, and dry under vacuo. Pale while solid was obtained as the copper acetylide. Yield (376.0 mg, 80%). Crystals were grown by slow diffusion of pentane to the saturated solution in dichloromethane. The structure details were shown as follows. 5 C58 N1 Cu1 N4 C12 C31 Cu2 N3 N2 C57 Figure S1. X-ray diffraction of copper acetylide (S-I) in the solid state. Hydrogen atoms were emitted for clarity. Table S1. Crystal data and structure refinement for S-I. Identification code 20161206ZJA_0m_a Empirical formula C58 H58 Cu2 N4 O0 Formula weight 938.16 Temperature 296(2) K Wavelength 0.71073 Å Crystal system Orthorhombic Space group Pbca Unit cell dimensions a = 19.5091(12) Å = 90°. b = 19.9327(12) Å = 90°. c = 26.1996(16) Å = 90°. Volume 10188.2(11) Å3 Z 8 Density (calculated) 1.223 Mg/m3 Absorption coefficient 0.875 mm-1 F(000) 3936 Crystal size 0.270 x 0.250 x 0.220 mm3 Theta range for data collection 2.043 to 25.008°. Index ranges -23<=h<=21, -21<=k<=23, -31<=l<=31 Reflections collected 31496 Independent reflections 8870 [R(int) = 0.0593] Completeness to theta = 25.008° 98.8 % Refinement method Full-matrix least-squares on F2 6 Data / restraints / parameters 8870 / 36 / 589 Goodness-of-fit on F2 1.358 Final R indices [I>2sigma(I)] R1 = 0.1987, wR2 = 0.3723 R indices (all data) R1 = 0.2486, wR2 = 0.4024 Extinction coefficient n/a Largest diff. peak and hole 0.777 and -0.817 e.Å-3 Table S2. Selected bond lengths [Å] and angles [°] for S-I. selected bond lengths [Å] selected angles [] C(12)-Cu(1) 1.911(14) N(1)-C(12)-Cu(1) 135.4(12) C(12)-N(1) 1.353(18) N(2)-C(12)-Cu(1) 120.4(10) C(12)-N(2) 1.35(2) N(4)-C(31)-Cu(1) 134.8(11) C(31)-N(4) 1.347(18) N(3)-C(31)-Cu(1) 122.4(10) C(31)-N(3) 1.402(19) C(31)-Cu(1)-C(12) 171.1(7) C(31)-Cu(1) 1.879(14) C(57)-Cu(2) 1.887(15) C(58)-Cu(2)-C(57) 167.8(7) C(58)-Cu(2) 1.86(2) 4.2 Procedure for the reaction of copper acetylide and 2a DCM [ IMes Cu Ph]n + 2a 3a + light yellow solid Eq. 2 40 oC complex I Isolated yield: 99% To a Schlenk tube was added octyl triflate (167.9 mg, 0.64 mmol) and dichloromethane (0.5 mL). The solution of complex 1 in dichloromethane (1.5 mL) was added to the tube dropwise at 40 oC. After 30 min, removed the solvent in vacuo and washed the residue with 5 mL of pentane for three times. The pentane filtrate was collected and concentrated. 3a (92.0 mg, 99% yield) was obtained after column chromatography with petroleum ether as the eluent. The solid that could not dissolve in pentane was isolated as light yellow solid (159.6 mg). Crystals were grown by slow 7 diffusion of pentane to the saturated solution in dichloromethane and light yellow precipitation left in the bottom. The X-Ray diffraction confirmed that the crystals are (IMes)2CuOTf (S-II), which might be produced from the decomposition of the expected (IMes)CuOTf. The structure details were shown as follows, which match well with the reference report for the same structure.8 N2 N3 C42 C12 Cu1 N1 N4 Figure S2. X-ray diffraction of the complex (S-II) which was crystalized from the reaction of Eq.2.