Catalytic Oxidative Cross-Coupling Polymerization of Unsymmetric Binaphthol Derivatives Using Cu(I)-Bisoxazoline Complexes

Abstract

ABSTRACT:The asymmetric oxidative coupling polymerization of 6,6 0 -dihydroxy-2,2 0 -binaphthalene derivatives or methyl 3,7-dihydroxy-2-naphthoate, having an unsymmetric 2-naphthol structure, with copper catalysts under an O 2 atmosphere was carried out. The polymerization using the CuCl-(S)-2,2 0 -isopropylidenebis(4-phenyl-2-oxazoline) catalyst afforded a polymer with a high cross-coupling selectivity of up to 99%, which showed a number average molecular weight of 5:0{9:1 Â 10 3 . To estimate the stereoselectivity during the polymerization, a model reaction was examined which resulted in good to high cross-coupling selectivities, while the enantioselectivities were low. The polymer composed of a homo-coupling unit showed a photoluminescence spectral pattern similar to that of the model compound. In contrast, a very different emission, which may be due to the excimer, from that of the model was observed for the polymer consisted of the cross-coupling unit.

Lewis-Acid-Assisted Highly Selective Oxidative Cross-Coupling Polymerization with Copper Catalysts

“…[11][12][13] However, as previously reported, the 1 H NMR spectrum of the obtained poly(2) hardly showed a clear peak splitting based on the coupling selectivity, and then it was estimated from the model reaction. 13 Therefore, further investigation of the unit ratio, that is, two homo-coupling units (X and Z) and a cross-coupling unit (Y), was performed.…”

“…[11][12][13] However, as previously reported, the 1 H NMR spectrum of the obtained poly(2) hardly showed a clear peak splitting based on the coupling selectivity, and then it was estimated from the model reaction. 13 Therefore, further investigation of the unit ratio, that is, two homo-coupling units (X and Z) and a cross-coupling unit (Y), was performed. Figure 1 depicts the 13 C NMR spectra of carbons attached to the hydroxyl group of the model homo-polymer, poly(3), the model compounds, 4 and 5, which correspond to the coupling units Y and Z in poly(2), respectively, and poly(2) obtained with the (+)PMP catalyst in the presence of Yb(OTf) 3 (entry 6) in dimethyl sulfoxide-d 6 (DMSO-d 6 ) (Scheme 4).…”

“…The cross-coupling reactions in the absence of the Lewis acid predominantly proceeded with a cross-coupling selectivity Y of 74-90% (entries 1-4). The observed cross-coupling selectivity for the polymerization using the (S)Phbox ligand, 90%, was slightly higher than that estimated from the model coupling reaction (80%), 13 probably due to the effect of the protecting group for the hydroxyl group, a methoxymethyl group, of the model monomers. Regardless of the copper catalyst, a significant increase in the crosscoupling selectivity was observed for the polymerization when the Lewis acid was used as the co-catalyst, and it reached 97% during the polymerization with the (S)Phbox ligand (entry 8).…”

“…This study focused on the polymerization of 3,7-dihydroxynaphthalene-2-carboxylate 2, which is facilely prepared from the commercially available acid by esterification and leads to a polymer bearing a mixture of three BINOL-unit structures, a crosscoupling (Y) and two homo-coupling ones (X and Z). 13 The polymerization with various copper catalysts in the presence of the Lewis acid (LA) was investigated (Scheme 3).…”

Direct synthesis of functional novolacs and their polymer reactions

“…Phenolic resins [1][2][3][4][5][6][7][8][9][10] and related polymers [11][12][13][14][15][16][17][18][19][20][21][22] are a very important class of common organic polymers, and have numerous applications in the development of materials [1][2][3][4][5][6] such as thermosetting resins, adhesives, photoresists and polymer composites. The main characteristics of phenolic resins, such as heat stability and mechanical properties, are attributed to their rigid rod-like polymer backbone of poly(phenylenemethylene).…”