F-butyl acrylate

Double hydrophilic star-block (PEO-fo-PAA)3 copolymers were prepared by a combination of anionic and ATRP of EO and fBuA [150]. Three-arm PEO stars, with terminal - OH groups were prepared by anionic polymerization, using l,l,l-tris(hydroxymethyl)ethane, activated with DPMK as a trifunctional initiator. The hydroxyl functions were subsequently transformed to three bromo-ester groups, which were utilized to initiate the polymerization of f-butyl acrylate by ATRP in the presence of CuBr/PMDETA. Subsequent hydrolysis of the f-butyl groups yielded the desired products (Scheme 74). 

Radical [3 + 2 cycloaddition. Cyclopentanes can be prepared by addition of alkenes across vinylcyclopropanes catalyzed by phenylthio radicals formed from (C6H5S)2 and AIBN. A Lewis acid such as A1(CH3)3 can increase the rate and the stereoselectivity of this radical initiated cycloaddition. Thus the combination of the vinylcyclopropyl ester 1 with f-butyl acrylate (2) provides the four possible cyclo-... 

In some instances, the resist polymer can be prepared in a single step by direct polymerization of the protected monomer(s) (37,88), entirely avoiding the intermediate PHOST. HOST-containing resist polymers have also been prepared by free-radical copolymerization of a latent HOST and a stable, acid-labile monomer, eg, the copolymerization of acetoxystyrene with /t /f-butyl acrylate, followed by selective removal of the acetoxy group (89) (Fig. 30). 

Novel spiropenicillins (Scheme 5) have also been prepared by Sheehan et al. [78]. (3,(3,(3-Trichloroethyl-6-diazopenicillanate 14 reacts with acrylonitrile, ethyl acrylate, and f-butyl acrylate to give isomeric compounds 16 and 17. The preferred mode of addition is from the sterically less hindered a-side. 

In some reactions, the choice of PTC can actually alter the distribution of products for example, the reaction of f-butyl acrylate with chloroform under basic phase transfer conditions gives two major products, as illustrated in Scheme 5.8, the amounts of which are catalyst dependent [46],... 

These results were slightly better than those obtained employing f-butyl acrylate to produce 9.97 (GC determination after cleavage). When 9.93 was treated with fluorescent substrate 9.92 without catalyst, the washed resin beads showed no fluorescence, proving the overall reliability of the fluorescent screening and the absence of interferences. 

Michael Addition. Titanium imide enolates are excellent nucleophiles in Michael reactions. Michael acceptors such as ethyl vinyl ketone, Methyl Acrylate, Acrylonitrile, and f-butyl acrylate react with excellent diastereoselection (eq 21 ). - Enolate chirality transfer is predicted by inspection of the chelated (Z)-enolate. For the less reactive unsaturated esters and nitriles, enolates generated from TiCl3(0-j-Pr) afford superior yields, albeit with slightly lower selectivities. The scope of the reaction fails to encompass p-substituted, a,p-unsaturated ketones which demonstrate essentially no induction at the prochiral center. Furthermore, substimted unsamrated esters do not act as competent Michael acceptors at all under these conditions. 

Becker et al. [64] functionalized a peptide, based on the protein transduction domain of the HIV protein TAT-1, with an NMP initiator while on the resin. They then used this to polymerize f-butyl acrylate, followed by methyl acrylate, to create a peptide-functionahzed block copolymer. Traditional characterization of this triblock copolymer by gel permeation chromatography and MALDI-TOF mass spectroscopy was, however, comphcated partly due to solubility problems. Therefore, characterization of this block copolymer was mainly hmited to ll and F NMR and no conclusive evidence on molecular weight distribution and homopolymer contaminants was obtained. Difficulties in control over polymer properties are to be expected, since polymerization off a microgel particle leads to a high concentration of reactive chains and a diffusion-limited access of the deactivator species. The traditional level of control of nitroxide-mediated radical polymerization, or any other type of controlled radical polymerization, will therefore not be straightforward to achieve. 

In a second article the same approach was used to synthesize a peptidic polymer containing the peptide Tritrpticin, a 13 residue antimicrobial peptide (Fig. 16) [66]. This time they initiated the polymerization of f-butyl acrylate, followed by styrene to produce a triblock copolymer, which clearly formed micelles in solution. Interestingly, the antimicrobial activity of the peptide was enhanced relative to the free peptide and the detrimental side effects normally associated with antimicrobial peptides, such as a high hemolytic activity, were reduced, highhghting the benefits of using peptide polymer hybrids in place of peptides alone. 

A half-metallocene iron iodide carbonyl complex Fe(Cp)l(CO)2 was found to induce the hving radical polymerization of methyl acrylate and f-butyl acrylate with an iodide initiator (CH3)2C(CO2Et)l and Al(Oi- Pr)3 to provide controlled molecular weights and rather low molecular weight distributions (Mw/Mn < 1.2) [79]. The hving character of the polymerization was further tested with the synthesis of the PMA-fo-PS and PtBuA-fi-PS block copolymers. The procedure efficiently provided the desired block copolymers, albeit with low molecular weights. 

Fig. 15.2.35. Solid state C CP/MAS spectra of three samples of poly(methyl methacrylate) crosslinked with 5 (lower), 20 (mid) and 50 (top) % of f-butyl acrylate end-capped oligomer containing ca. 2-3 HDDA repeat units.

Alternatively, hyperbranched polymers can be prepared in situ on the monolayer surface. Treatment of the acid-terminated layer with chloroformate and amine-terminated poly(f-butyl acrylate) produces ester groups on the surface. Hydrolysis of the ester functions with tosic acid gives carboxyl groups. The whole procedure is then repeated several times... 

The enolatc of (2S,4R)-I can also undergo Michael addition to f-butyl acrylate. The yield is low, but the adduct is obtained in 98% ee. This reaction provides a route to a derivative of 2-methylglutamic acid (equation I). 

A dramatic development in the anionic polymerization of acrylate and methacrylate monomers was the discovery that by addition of lithium chloride it was possible to effect the controlled polymerization of f-butyl acrylate [122]. Thus, using oligomeric (a-methylstyryl)lithium as initiator in THE at -78 °C, the molecular weight distribution of the... 

Figure 10-20. Glass-transition temperatures Tg of free-radically-polymerized copolymers of styrene and acrylic acid (AS), acrylamide (AA), f-butyl acrylate (BA), and butadiene (BU) as a function of the mole fraction o styrene monomeric units (after K. H. Illers).

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