Olefin Metathesis

In this study, we report on for the first time the self-metathesis of the chicle gum and cross-metathesis of the chicle gum rubber isolated from the gummy latex of sapodilla (Manilkara zapota) with orange oil, β-pinene and, methyl methacrylate using the Ru-alkylidenes Hoveyda-Grubbs and Grubbs second generation catalysts. There were obtained terpene- and ester-terminated oligoisoprenes, with good yields and selectivities. The present results are a promising starting point for the application of this underexploited renewable resource as a new feedstock for metathesis transformations.

En este estudio reportamos por primera vez, la auto-metátesis de la goma de chicle y la metátesis cruzada del hule de la goma de chicle aislada del látex del chicozapote (Manilkara zapota) con aceite de naranja, β-pineno y metacrilato de metilo, usando los catalizadores Ru-alquilidenos Hoveyda-Grubbs y Grubbs de segunda generación. Se obtuvieron oligoisoprenos con grupos terminales terpeno y éster con buenos rendimientos y selectividades. Los presentes resultados son un punto de partida prometedor para la aplicación de este poco explotado recurso renovable como materia prima para las transformaciones vía metátesis.

he ammonium tagged Hoveyda-type
catalyst bearing sterically enlarged N-heterocyclic carbene
ligand was synthesized and supported on SBA-15. The
obtained heterogeneous olefin metathesis catalyst forms
unprecedentedly stable Ru-methylidenes and provides
products of ring-closing and cross metathesis with
turnover numbers (TONs) up to 35 000 and turnover
frequencies (TOFs) up to 1590 min−1. The catalyst proved
to be truly recyclable and effective in a continuous flow
mode.

Allylisothiocyanateundergoes self-metathesis by 2 nd generation Grubbs catalyst to give 1,4-disothiocyanatobut-ene together with the release of styrene and phosphine ligands. Despite the release of both ligands cross metathesis with methyl oleate, ethyl oleate and ethyl linoleatestill gave some targeted cross and self-metathesis products.1-isothiocyanatoundec-2-ene was detected in all the cross-metathesis reaction. Methyl11-isothiocyanatoundec-9-enoate and ethyl-11-isothiocyanatoundec-9-enoateare products of another cross-metathesis with methyl oleate and ethyl oleate respectively. Under the reaction conditionno other cross product with ethyl linoleate was detectedexcept the formation of side products ofcarbene species possibly due to side reactions such as isomerization and addition. The formation of 1-isothiocyanatomethylstyreneis the result of the cross metathesis between allylisothiocyanate and styrene. The study indicated that the sulfur atom is more sensitive than oxygen atom to interact with the catalyst resulting in the release of the phosphine and styrene from catalytic cycle. Therefore a suitable protecting agent is necessary to sustain the catalytic cycle.

New heterogeneous, reusable catalysts for olefin metathesis have been prepared by immobilizing theHoveyda–Grubbs first generation type alkylidene (commercially available as the Zhan catalyst-1C) onsiliceous mesoporous molecular sieves with different pore sizes and architectures (SBA-15, SBA-16,MCM-41 and MCM-48) having the surface modified with molecules bearing dicyclohexylphosphine(PCy2) end groups. Resulting novel heterogenized catalysts proved high activity in ring-closing metathesis(RCM) of 1,7-octadiene, diethyl diallylmalonate, tert-butyl N,N-diallylcarbamate and N,N-diallyl-2,2,2-trifluoroacetamide, in homometathesis of 1-decene, 5-hexenyl acetate and methyl 10-undecenoate,and in cross-metathesis (CM) of allylbenzene with cis-1,4-diacetoxy-2-butene. The catalytic activitydecreased with decreasing pore size of supports in the order SBA-15 > MCM-48 > SBA-16 and MCM-41.Filtration test suggested that the solid catalyst was responsible for the catalytic activity. Catalysts wereeasily separated from the reaction mixtures and products of low levels of Ru concentration were obtained.

Fort he first time,o lefin cross metathesis has been developed for vinylgermanium compounds. This paper also marks the first case of transition metal-catalyzed functionalization of heterosilses-quioxanes,w hich in our case are cubic vinylgermasil-sesquioxanes and newly synthesizedd i(vinylgermyl)-substituted doubledecker silsesquioxane.T hese processes leadt oaseries of new molecular, unsaturated mono-a nd divinyl-substituted germasilsesquioxanes, which can be potentially applied as precursors for optoelectronics and for the synthesis of new advanced materials.A dditionally,p reliminary tests of metathetic copolymerization of divinylsubstituted double-deckerd igermasilsesquioxanes (DDSQ-2ViGe) with selected diolefins provedt ob ev ery promising and resulted in the synthesis of novels te-reoregular trans-germasilsesquioxyl-vinylene-phenyl-ene macromolecular derivatives.A ll newly obtained compounds were isolated andc haracterized by mass and spectroscopic methods.