Catalytic Stereocontrol by Scandium Trifluoromethanesulfonate in Radical Polymerization of α-(Alkoxymethyl)acrylates

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The effects of Lewis acids, that is, rare earth metal trifluoromethanesulfonates, on the free-radical polymerization of N-methylmethacrylamide (MMAM), Nisopropylmethacrylamide (IPMAM), N-tert-butylmethacrylamide (tBMAM), N-phenylmethacrylamide (PMAM), and methacrylamide were examined under various conditions. A catalytic amount of Yb(OSO 2 CF 3 ) 3 significantly affected the stereochemistry during the radical polymerization. Polymerization solvents strongly influenced the effect of the Lewis acids. Methanol was the best solvent for increasing the isotactic specificity during the polymerization of MMAM and IPMAM, whereas tetrahydrofuran was more effective for the tBMAM and PMAM polymerizations.

Section: Introductionmentioning

confidence: 99%

Stereocontrol during the free‐radical polymerization of methacrylamides in the presence of Lewis acids

Isobe

Suito

Habaue

2003

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“…However, radical polymerization, although it can be applied to a wide variety of monomers, is not suitable for preparing stereoregular polymers 7–12. Recently, we reported that the addition of catalytic amounts of Lewis acids significantly affected the tacticity during the radical polymerization of α‐(alkoxymethyl)acrylates,13–16 methacrylates,17 and (meth)acrylamides 18–22. For example, N ‐isopropylmethacrylamide (IPMAM) afforded an isotactic‐rich polymer [up to 58% meso triad ( mm )] in the presence of yttrium trifluoromethanesulfonate [Y(OTf) 3 ] at 60 °C in tetrahydrofuran (THF), whereas a syndiotactic‐rich polymer ( rr = 68%) was obtained in the absence of the Lewis acid under the same conditions 19–22.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and chiral recognition ability of optically active poly{N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide} with various tacticities by radical polymerization using Lewis acids

Morioka¹,

Suito²,

Isobe³

et al. 2003

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The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)3] and scandium trifluoromethanesulfonate [Sc(OTf)3]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)3 in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr2 proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003

“…Mero and Porter10 suggested that scandium trifluoromethanesulfonate [Sc(OTf) 3 ] may alter the stereochemistry of acrylamide polymerization. Recently, we found that Lewis acids influenced the stereochemistry during the polymerizations of vinyl esters11 and α‐(alkoxymethyl)acrylates 12, 13. The use of Al(OtBu) 3 increased the syndiotactic specificity during vinyl acetate polymerization,11 and during the polymerization of α‐(alkoxymethyl)acrylates, a catalytic amount of Sc(OTf) 3 induced isotactic‐specific propagation, whereas the addition of ZnBr 2 produced a syndiotactic polymer 12, 13…”

Section: Introductionmentioning

confidence: 99%

Stereocontrol during the free‐radical polymerization of methacrylates with Lewis acids

Isobe

Nakano

Okamoto

2001

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109

The free‐radical polymerizations of methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, and 2‐methoxyethyl methacrylate were carried out in the presence of various Lewis acids. The MMA polymerization in the presence of scandium trifluoromethanesulfonate [Sc(OTf)3] in toluene or CHCl3 produced a polymer with a higher isotacticity and heterotacticity than that produced in the absence of Sc(OTf)3. Similar effects were observed during the polymerization of the other monomers. ScCl3, Yb(OTf)3, Er(OTf)3, HfCl4, HfBr4, and In(OTf)3 also increased the isotacticity and heterotacticity of the polymers. The effects of the Lewis acids were greater in a solvent with a lower polarity and were negligible in tetrahydrofuran and N,N‐dimethylformamide. Sc(OTf)3 was also found to accelerate the polymerization of MMA. On the basis of an NMR analysis of a mixture of Sc(OTf)3, MMA, and poly(methyl methacrylate), the monomer–Sc(OTf)3 interaction seems to be involved in the stereochemical mechanism of the polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1463–1471, 2001