Phenylacetylene dimerization promoted by ruthenium(II) complexes

Pyridine‐Enhanced Head‐to‐Tail Dimerization of Terminal Alkynes by a Rhodium–N‐Heterocyclic‐Carbene Catalyst

“…The reaction course was monitored by 1 H NMR spectroscopy, and the conversion was determined by integration of the corresponding resonances of the alkyne and the products. ), 6.90, 6.67 (both d, J HÀH = 1.7 Hz, 2 H, =CHN), 6.72 (overlapped, H p-py (b) ), 6.43 (t, J HÀH = 6.5 Hz, 2 H, H ppy(a) ), 6.41, 6.27 (both dd, J HÀH = 6.3, 5.2 Hz, 2 H, H m-py (b) ), 6.08 (dd, J HÀH = 6.5, 5.4 Hz, 2 H, H m-py(a) ), 3.93, 3.89, 3.84, 3.65 (all sept, J HÀH = 6.5 Hz, 4 H, CHMe IPr ), 1.78, 1.76, 1.56, 1.53, 1.23, 1.19, 1.10, 1.08 (all d, J HÀH = 6.5 Hz, 24 H, CHMe IPr ), 0.43 (s, 9 H, H SiÀMe ), À16.47 ppm (d, J RhÀH = 21.6 Hz, 1 H, RhÀH); 13 Computational details: The geometry of all structures was optimized with the G09 program package [42] at the DFT level by using the B3LYP approximation [43] combined with the 6-31GA C H T U N G T R E N N U N G (d,p) basis set for H, C, N, Cl, and Si atoms [44] and the SDD pseudo-potential [45] for the Rh atoms. The nature of the stationary points was confirmed by frequency analysis, and the intrinsic reaction paths were traced by connecting the transition structures with the respective minima.…”

“…Competitively to the formation of head-to-head (E/Z) and head-to-tail (gem) enynes, other products such as butatrienes, [6] diynes, [7] dieneynes, [8] cyclotrimers, [9] oligomers, [10] or polymers [11] can also be obtained, depending on the catalyst and reaction conditions (Scheme 1). A broad range of catalysts based on Pd, [12] Ru, [13] Rh, [14] Ni, [15] Ir, [16] Fe, [17] Au, [18] Co, [19] Os, [20] Ti, [21] Zr, [22] Re, [23] Y, [24] Sc, [25] Hf, [26] Cr, [27] lanthanides, [28] actinides, [29] or main group elements [30] can promote alkyne dimerization, albeit with different grades of success with regard to selectivity. In particular, preferential preparation of head-to-tail enynes has been disclosed for aroA C H T U N G T R E N N U N G mat-A C H T U N G T R E N N U N G ic [13i, 14e, 16b, 24a] or aliphatic [12d, 14a,c,g,k, 22a, 24c, 26, 29b] alkynes, although examples of selective initiators regardless of the substituent on the alkyne are limited to the catalysts of Nakamura (Ti), [21a] Trost (Pd), [12b] Eisen (Al), [30b] and Zhang (Au) [18] and their respective co-workers.…”

C–C coupling reactions in the coordination sphere of rhodium(i) and rhodium(iii): New routes for the di- and trimerization of terminal alkynes

“…The organic products were characterized by comparison of the NMR data with those reported in the literature. 5,20, 21 Method b. A solution of (Z)-7 (39 mg, 0.06 mmol) in acetoned 6 (0.5 cm 3 ) was treated with CF 3 CO 2 H (0.0047 cm 3 , 0.06 mmol) and stirred for 20 min at room temperature.…”

“…The organic products were characterized by comparison of the NMR data with those reported in the literature. 5,7,20,21 Reaction of (E)-8 with carboxylic acids. Method a.…”

Methimazolyl based diptych bicyclo-[3.3.0]-ruthenaboratranes

“…Under more forcing conditions, with an excess of HCºCPh, the hydride precursor [RuHCl(CO) 26 which is an effective alkyne dimerization catalyst. 27 The yet to be isolated species 'RuCl(CºCPh)(CO)(PPh3)n' (n = 2,3) being plausible resting states that might react with Na[H2B(mt)2] to afford 8. The mild conditions under which 8 forms would seem to argue against this.…”