End-Functionalized Polymerization of 2-Vinylpyridine through Initial C–H Bond Activation of N-Heteroaromatics and Internal Alkynes by Yttrium Ene–Diamido Complexes

Abstract

We successfully introduced end-capping functional groups to poly(2-vinylpyridine)s by initial introduction of the functional groups on yttrium catalysts through C-H bond activation of heteroaromatics and internal alkynes to the Y center via alkylyttrium-mediated σ-bond metathesis.

2,2′-Bipyridyl formation from 2-arylpyridines through bimetallic diyttrium intermediate

“…Because of the stability of the +3 oxidation state of the rare-earth metal center, C–C bond formation products, biaryls and diynes, have been trapped in their dianionic form to give bimetallic complexes such as C and D as reported by Fryzuk et al (Fig. 1), 5,8,9 even though access to low-valent rare-earth metal complexes has been reported by Evans et al 10 In our studies on the C–H bond activation of heteroaromatic compounds by rare-earth metal and early transition metal complexes, 11 we found that σ-bond metathesis and subsequent 2,2′-bipyridyl formation from 2-arylpyridines proceeded upon treatment of an alkyl complex of (ethylenediamido)yttrium ( 1 ) with 2-arylpyridine ( 2 ). During this transformation, the C–H bond adjacent to the nitrogen atom of the pyridine ring was selectively functionalized.…”

Synthesis of Pyridine- and 2-Oxazoline-Functionalized Vinyl Polymers by Alane-Based Frustrated Lewis Pairs

“…More drastically, replacing Al(C 6 F 5 ) 3 with B(C 6 F 5 ) 3 or AlEt 3 led to a completely inactive polymerization system (runs 8 and 9). Polymerizations employing the preformed monomer-LA adduct, (2-VP)·Al(C 6 F 5 ) 3 , afforded the results similar to those by the toluene adduct, (toluene) 0.5 ·Al(C 6 F 5 ) 3 (runs 10-13 vs. runs [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Also noteworthy is that, when carried out in CH 2 Cl 2 or DMF, the above polymerizations were much less effective or completely shut down, attributable to rapid deactivation of Al(C 6 F 5 ) 3 in CH 2 Cl 2 15 or impeding of the monomer activation by virtue of strong coordination of DMF to Al(C 6 F 5 ) 3 .…”

“…Indeed, controlled polymerization of 2-VP has been achieved. 11,12 However, to date there has been no report on the polymerization of 2-VP and iPOx by FLPs. Accordingly, we disclose herein our results on the polymerization of 2-VP, iPOx, and 4-methyl-2-isopropenyl-2-oxazoline (MiPOx) by FLPs and CLPs consisting of LAs [including Al(C 6 F 5 ) 3 , B(C 6 F 5 ) 3 , MeAl(BHT) 2 (BHT = 4-Me-2,6-t-Bu 2 C 6 H 3 O) 13 and AlEt 3 ] and LBs [including phosphines t-Bu 3 P, Mes 3 P (Mes = 2,4,6-Me 3 C 6 H 2 ) and Ph 3 P], and N-heterocyclic carbene (NHC) bases [including 1,3-ditert-butylimidazol-2-ylidene (It-Bu), 1,3-di(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-trizazol-5-ylidene (TPT)] (Scheme 1).…”

Highly Isotactic and High-Molecular-Weight Poly(2-vinylpyridine) by Coordination Polymerization with Yttrium Bis(phenolate) Ether Catalysts

“…polymerization of 2-VP through initial C-H bond activation of N-heteroaromatics. 6 Thus, the development of effective polymerization catalysts that can produce highly isotactic poly(2-VP) with high-M n still requires further studies.…”