High-Load, Hybrid Si-ROMP Reagents

Abstract

The combination of norbornenyl-tagged (Nb-tagged) silica particles and functionalized Nb-tagged monomers for the generation of hybrid Si-ROMP reagents and scavengers is reported. Specifically Si-ROMP-derived bis-acid chloride, dichlorotriazine and triphenylphosphine scavenger/reagents have been grafted from the surface of silica particles utilizating surface-initiated, ring-opening metathesis polymerization (ROMP). These hybridpolymeric materials combine the physical properties of current immobilized silica reagents and represent a key advancement in load by merging the inherent tunable properties of the ROMP-derived oligomers with silica supports for application in parallel synthesis.

Visible-Light Photoredox-Catalyzed Amidation of Benzylic Alcohols

“…N-Benzylbenzamide (3av). 32 Brown solid (167 mg, 79% yield); mp 104−105 °C, R f = 0.42 (hexane/ethyl acetate 3.5/1.5). 1 H NMR (400 MHz, CDCl 3 ) δ: 7.79 (d, J = 7.3 Hz, 2H), 7.48 (d, J = 7.4 Hz, 1H), 7.40 (t, J = 7.5 Hz, 2H), 7.34 (d, J = 4.4 Hz, 4H), 7.31−7.26 (m, 1H), 6.68 (s, 1H), 4.62 (d, J = 5.7 Hz, 2H).…”

Silica-Supported Oligomeric Benzyl Phosphate (Si-OBP) and Triazole Phosphate (Si-OTP) Alkylating Reagents

“…It was observed that, the use of (MeO) 3 Si-(CH 2 ) 2 -Nb ( 2 ) dramatically increased the norbornene load of Si-Nb ( 3 ), compare to 5-(bicycloheptenyl)-triethoxysilane [Nb-Si(OEt) 3 ], which was previously used for silica tagging. 23 By this optimized method, we prepared norbornene-functionalized silica 3 (Si-Nb) on gram scale with 0.4 mmol/g loading (determined by modified bromine titration method). 29 With this Si-tagged nanoparticle ( 3 ) in hand, a metathesis catalyst-armed surface-initiated polymerization was established using the C848 [Grubbs 2 nd generation catalyst, G-II ) 30 (20 mol%, based on Si-Nb load) in CH 2 Cl 2 and toluene as solvents, followed by addition of the Nb-tagged benzyl phosphate monomer 4 to rapidly generate the desired hybrid material 5a , silica oligomeric benzyl phosphate (Si-OBP n ).…”

“…In this fashion, silica-supported ROMPgel acid chloride, dichlorotriazine, and triphenylphosphine reagents were generated with properties nearly identical to the equivalent soluble ROMPgel oligomeric reagents. 23 …”

Opportunities of Immobilized Homogeneous Metathesis Complexes as Prominent Heterogeneous Catalysts

“…Since 2007, many other strategies have been developed for modification of diverse surfaces by grafting. These include (norbornene)‐functionalized gold surfaces, Wang and Merrifield resins, electro‐polymerized films, metals and metal oxides, silica particles, cellulose fibers, montmorillonite clay, quartz surfaces, polydimethylsiloxane, and graphene oxide . An example of a supported G1 catalyst through the alkylidene ligand on cellulose fibers is shown in Scheme ( 19 ) …”