Degradation of the ruthenium-based metathesis catalyst [RuCl2(CHPh)(H2IPr)(PCy3)] with primary alcohols

Synthesis of Dihydrofurans and Dihydropyrans with Unsaturated Side Chains Based on Ring Size‐Selective Ring‐Closing Metathesis

“…That ruthenium atoms in metathesis catalysts display a certain oxophilicity, especially to alcohols, is underlined by a number of literature reports, describing, e.g., the formation of chelates if hydroxyalkyl side chains are attached to ligands, [57,58] alkoxy-substitued ruthenium carbenes, [59] or the significant rate enhancement of A upon addition of phenols. [60] The interaction of hydroxy groups with metathesis catalysts can, however, also be a source of trouble, as it is known that alcohols induce a degradation of Grubbs catalysts to ruthenium hydride species, [61][62][63] that may catalyze isomerization [64] or degradation [65] of the substrate. [52,53] However, in our experiments we could not detect any products resulting from an undesired nonmetathesis transformation of the unprotected alcohol 5d.…”

Fette und Öle als nachwachsende Rohstoffe in der Chemie

“…Dabei wurden ungewollte Nebenreaktionen, geringe Umsätze sowie schlechte Selektivität beobachtet, [122] wahrscheinlich weil Alkohole Ruthenium-Metathesekatalysatoren zersetzen können. [123] Um dies zu umgehen, wurden die gewünschten w-Hydroxyfettsäureester mittels KM von acetatgeschützten Fettalkoholen mit Methylacrylat in einer effizienten katalytischen Reaktion hergestellt. [122] Im Gegensatz hierzu war die Schutzgruppenstrategie bei der KM von 5 b nicht erforderlich (Schema 15), was darauf hindeutet, dass sekundäre Alkohole von den unterSchema 11.…”

Ruthenium‐Catalyzed Ring‐Closing Metathesis: Recent Advances, Limitations and Opportunities

“…As noted in the Introduction, catalysts C1 [26], C2 [27], and related NHC catalysts [28] are readily decomposed by primary alcohols (particularly in the presence of base), undergoing conversion into hydridocarbonyl species such as C7 or C8, and other, unidentified inorganic products. Importantly, the vinyl ethers often used to terminate Ru-catalyzed metathesis reactions can also trigger formation of hydride products.…”

“…This robustness should not be overstated, however: while many of the precatalysts exhibit reasonable stability toward oxygen, particularly in the solid state, the active catalyst is oxygen-sensitive [19][20][21][22]. In addition, an increasing number of reports describe sensitivity toward protic functionalities (particularly allylic alcohols [23][24][25] and alcohol solvents) [26][27][28][29]. A susceptibility to poisoning by soft donors such as phosphine or sulfide groups has been suggested [5,15], which may inhibit, if not necessarily arrest [30,31], metathesis.…”