Expedient synthesis of conjugated triynesviaalkyne metathesis

Abstract

The first synthesis of symmetrical and dissymmetrical conjugated triynes by self- and cross-metathesis was successfully achieved thanks to the use of hindered diynes.

Catalytic Alkyne and Diyne Metathesis with Mixed Fluoroalkoxy-Siloxy Molybdenum Alkylidyne Complexes

“…In the presence of I (3 mol %, 40 °C, 3 h), 1,6-bis­(triisopropylsilyl)-1,3,5-hexatriyne ( 10a ) formed with high selectivity over the corresponding symmetrical 1,3-butadiyne and could be isolated in 63% yield after silica gel chromatography. Significantly lower selectivity toward triyne formation was observed for other substrates such as 9b , which afforded 10b as a complex mixture with the corresponding diyne, tetrayne, and possibly higher polyynes . Hence, the diyne disproportionation of 9a and 9b was investigated under similar conditions in the presence of MoF9 , MoSiF9 , and MoSi*F9 (Scheme ).…”

“…R = Mes, furnished a considerable drop of selectivity with lower triyne/diyne ratios, leaving the quest for more efficient catalysts with higher selectivity and productivity. 61 The tri(tert-butoxy)siloxide ligand was also employed for the preparation of the mixed fluoroalkoxy-siloxy complex MoSiF6 (Figure 1), which served as a model complex for the silica-supported catalyst MoF6@SiO2. The homogeneous catalyst MoF6 and its immobilized form MoF6@SiO2 showed unprecedented catalytic activity at parts-per-million loadings; however, lower activity was observed for the heterogeneous system, presumably owing to the rigidity of the surface species.…”

“…In fact, an expedient synthesis of conjugated triynes from sterically hindered 1,3-pentadiynes, for example, with R = i Pr 3 Si and R′ = Me, in the presence of catalyst I was recently reported. Nevertheless, less sterically demanding groups, for example, R = Mes, furnished a considerable drop of selectivity with lower triyne/diyne ratios, leaving the quest for more efficient catalysts with higher selectivity and productivity …”

183W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis

“…Molybdenum alkylidyne complexes endowed with triarylsilanolate ligands such as 1, the corresponding ate-complex 2 and the derived bench-stable phenanthroline adduct [1•-(phen)] set the standards in the field of alkyne metathesis (Figure 1). [1][2][3][4][5] Their functional group compatibility is largely unrivaled; [6][7][8][9][10] it has recently been further improved by the development of a second catalyst generation distinguished by a tripodal silanolate ligand framework. [11,12] Specifically, the "canopy complex" 3 and relatives maintain the virtues of the parent complex 1, yet allow the chelate effect to be harnessed in form of an improved stability towards protic sites; in conjunction with the well-balanced electrophilic character and proper steric protection of the operative Mo CR unit, this results in an excellent overall application profile.…”

183W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis

“…Molybdenum alkylidyne complexes endowed with triarylsilanolate ligands such as 1,the corresponding ate-complex 2 and the derived bench-stable phenanthroline adduct [1•-(phen)] set the standards in the field of alkyne metathesis (Figure 1). [1][2][3][4][5] Their functional group compatibility is largely unrivaled; [6][7][8][9][10] it has recently been further improved by the development of asecond catalyst generation distinguished by at ripodal silanolate ligand framework. [11,12] Specifically,t he "canopy complex" 3 and relatives maintain the virtues of the parent complex 1,yet allow the chelate effect to be harnessed in form of an improved stability towards protic sites;i n conjunction with the well-balanced electrophilic character and proper steric protection of the operative Mo CR unit, this results in an excellent overall application profile.…”