Hoch aktive und belastbare Katalysatoren für die Alkinmetathese

Abstract

Gratwanderung: Jüngere Fortschritte bei Alkinmetathese‐Katalysatoren beruhen auf der Entwicklung maßgeschneiderten Liganden, die einerseits die Aktivität der Katalysatoren und andererseits ihre Beständigkeit verbessern (siehe Schema; M=W, Mo; R=CR′, N). Wichtige Kriterien sind die Elektrophilie und die Substrat‐Bindestellen am Übergangsmetallzentrum.

Identification and Synthesis of Macrolide Pheromones of the Grain Beetle Oryzaephilus Surinamensis and the Frog Spinomantis Aglavei

“…[15] To overcome this problem, we planned to use an alternative approach employing ring-closing alkyne metathesis (RCAM), [16] in particular with regard to the recent progress in the development of highly active homogeneous alkyne metathesis catalysts. [17] One double bond is conventionally introduced into an alkyne-containing precursor, which is then subjected to RCAM, followed by Lindlar hydrogenation to the final product. A prerequisite of this approach is that alkyne metathesis is strictly orthogonal to alkene metathesis, [16,17] leaving the double bond unaffected by the metal alkylidyne catalysts.…”

“…[17] One double bond is conventionally introduced into an alkyne-containing precursor, which is then subjected to RCAM, followed by Lindlar hydrogenation to the final product. A prerequisite of this approach is that alkyne metathesis is strictly orthogonal to alkene metathesis, [16,17] leaving the double bond unaffected by the metal alkylidyne catalysts. Independently from us, this strategy was recently used by Fürstner et al in the total synthesis of lactimidomycin [18] and in the total synthesis of the antimitotic agent leiodermatolide.…”

“…The starting compound for the synthesis of the Wittig salt 14 was pent-3-yn-1-ol (16), which was first converted into the iodide and then transformed into the Wittig salt 14. Secondly, 5-hexen-oic acid (17) was esterified with methanol, and the resulting ester was oxidatively cleaved with RuCl 3 and NaIO 4 affording aldehyde 18. [20] Compound 14 and aldehyde 18 were coupled in a stereoselective Z configured Wittig reaction with sodium bis(trimethylsilyl)amide (NaHMDS), [21] yielding the desired ester in excellent stereoselectivity (Z/E = 99.5:0.5).…”

Conjugated BODIPY DYEmers by Metathesis Reactions

“…Alkyne metathesis has witnessed tremendous recent advances with the development of several well-characterized molybdenum and tungsten alkylidyne complexes, which are able to promote the catalytic breaking and making of CC bonds with remarkable activity, functional-group tolerance, and reliability. [11] Typically, and depending on the catalyst employed, an internal alkyne is required for a successful alkyne metathesis reaction. [12] Most known cases have used a 1-propyne substituent for this purpose because the second metathesis product, 2-butyne, is volatile and can easily be removed from the reaction if run under slightly reduced pressure or in the presence of an absorbing material.…”

A Tetrameric Cage with D2h Symmetry through Alkyne Metathesis

“…Alkyne metathesis [27][28][29][30][31][32][33][34][35] has emerged as an alternative viable dynamic covalent reaction. It has been widely practiced in the synthesis of natural products, [28,36] shape-persistent macrocycles, [37] and polymers.…”