1-Phenylethyl vinyl ether

Poly(l,4-pentadiene-alt-MA), 343, 348, 586 Poly(phenanthrene-alt-MA), 376, 660 Poly(phenylacetylene), MA grafted, 471 Poly(phenylacetylene-co-MA), 335, 660 Poly(2-phenylallyl alcohol-alt-MA), 331, 660 Poly(4-phenyl-l-butene-alt-MA), 340, 341 Poly(/- 1-phenylethyl methacrylate-co-MA), optically active polymer, 383 Poly(/-1-phenylethyl vinyl ether-alt-MA), optically active polymer, 383 Poly(5-phenyl-l-pentene-alt-MA), 340, 341 Poly( l-phenyl-4-pentene- 1-one-alt-MA), 314 Poly(3-phenyl propene-l-alt-MA), 341 Poly(o-phenylstyrene-alt-MA), 373 Poly(2-phenylvinyl alkyl ethers-alt-MA), 318 Poly(2-phenylvinyl alkyl thioethers-alt-MA), 318 Poly(phenyl vinyl ether-alt-MA), 318, 394 Poly(phenyl-o-vinyl formal-alt-MA), 328 Poly(phenyl vinyl ketone-co-MA), physical properties, 290... 

The stereoelective polymerization of a racemic vinyl ether in the presence of an optically active catalyst has been attempted (192), but not achieved. On the other hand, the cationic copolymerization of racemic 1-methylpropyl vinyl ether with (S)-l-phenylethyl vinyl ether or (R)-1-phenylethyl vinyl ether was shown (193) to be stereoelective in the presence of the heterogeneous catalyst A1(O-i.C H )3/H2SO4. 

The degree of induced diastereoselectivity in the rhodium-catalyzed hydroformylation of ( + )-(i )-l-phenylethyl vinyl ether is much higher (linear/branched 43 57, branched d.r. 81 19) than with the related alkene 4-phenyl-l-pentene (linear/branched 2 1, branched d.r. 49 51). Other chiral olefins with the stcrcogenic carbon atom directly linked to the double bond also give lower diastereoselectivities (d.r. <36 64 in all cases)102. 

Optically active copolymers of (-)-l-phenylethyl methacrylate and MA have also been prepared.The copolymer remained optically active even after removal of the optically active ester group pendent on the polymer backbone. The copolymers were not strictly 1 1 alternating materials, such as the (-)-l-phenylethyl vinyl ether-MA copolymers. The work on these optically active copolymers is an excellent demonstration of the importance of steric effects in determining the configuration of a newly formed repeating unit on a polymer backbone. 

Phenylbutene-2-yl)succinic anhydride, optically active ene product, 168 Phenylcarbene, dimerization to stilbene, 203 Phenylcyclohexane, acylation with MA, 92 Phenyldichlorophosphine MA copolymerization, 297 styrene copolymerization, 297 (-)-l-Phenylethyl methacrylate, MA copolymerization, 383 (-)-l-Phenylethyl vinyl ether, MA copolymerization, 383... 

Methyl-1 -phenylethyl)-4-(2-propynyloxy)benzene, 3760 I Methyl vinyl ether, Acids, 1221 Nitrilotris(oxiranemethane), 3181... 

The Lewis acid-promoted tandem inter[4 + 2]/intra[3 + 2]-cycloaddition of the (fumaroyloxy)nitroalkene (124) with the chiral /i-silylvinyl ether (125) is the key step in the total synthesis of (+)-crotanecine (126), the necine base of a number of pyrrolizidine alkaloids (Scheme 46).237 The tandem inter[4 + 2]/intra[3 + 2]-cycload-ditions of nitroalkenes (127) with dipolarophiles attached to the /f-carbon of a vinyl ether (128) provides a method of asymmetric synthesis of highly functionalized aminocyclopentanes (129) (Scheme 47).238 trans-2-( 1 -Methyl-phenylethyl)cyclohex-anol has been developed as a new auxiliary in tandem 4 + 2/3 + 2-cycloadditions of nitroalkenes.239 The scope and limitations of the bridged mode tandem inter-[4 + 2]/intra[3 + 2]-cycloadditions involving simple penta-1,4-dienes are described in detail.240 A tandem intermolecular/intramolecular Diels-Alder cycloaddition was successfiilly used to synthesize a B/C cA-fused taxane nucleus (130) in 50% overall... 

The rates of initiation and propagation are comparable when the covalent initiator and dormant chain ends have similar structures. Therefore, 1-phenylethyl precursors are useful initiators for styrene polymerizations, but are poor initiators for a-methylstyrene and vinyl ether polymerizations. Similarly, cumyl derivatives are good initiators for isobutene and styrene, but are poor initiators for vinyl ethers their initiation of a -methylstyrene is apparently slow [165]. 1-Alkoxyethyl derivatives are successful initiators for vinyl ethers, styrenes, and presumably isobutene polymerizations [165,192]. /-Butyl derivatives initiate polymerization of isobutene slowly [105]. This is mirrored in model studies that show that /-butyl chloride undergoes solvolysis approximately 30 times slower than 2-chloro-2,4,4-trimethylpentane [193]. This may be due to insufficient B-strain in monomeric tertiary precursors [194]. In contrast, monomeric and dimeric or polymeric structures of secondary esters and halides apparently have similar reactivity. 

Controlled polymerization requires that the initiation rate is at least comparable to that of propagation. Initiation in controlled/living carbocationic systems is usually carried out using models of growing species in their dormant state (e.g., the adducts of a monomer with protonic acids). This enables a similar set of equilibria to be established between carbocations and dormant species for initiation and for propagation. For example, 1-phenylethyl halides have similar reactivity as the macromolecular dormant species in styrene polymerizations, and I-alkoxyethyl derivatives are as reactive as the macromolecular species in the polymerization of vinyl ethers [Eq. (38)] ... 

In parallel, a reaction engineering approach involving a scavenger reagent with intermediate reactivity with DMT was investigated. This scavenger compound would ideally be less reactive than the cis-ester, so it did not interfere with the oleflnation reaction but be more reactive than the vinyl ether. Screening experiments with a series of esters identified l,l-dimethyl-2-phenylethyl acetate (DMPEA) as a compound that had the desired reactivity. ... 

Fig. 2. Molar optical rotation [(0] f) ) vs polymerized monomer optical purity of isotactic vinyl polymers having the asymmetric carbon atom in the 7 position to the main chain. -O- poly-[(/J)-o -phenylethyl]-methacrylate -C- poly-(+)-menthylmethacrylate poly-(5 )-5-methyl-l-heptene poly-[(5 )-2-methylbutyl]-vinyl ether.

An important advantage of enol ether dienophiles is their use in asymmetric synthesis through attachment to a chiral auxiliary. Vinyl ethers derived from (+)-camphor, (l/ ,25)-2-phenylcyclohexanol, (7 )-2,2-diphenylcyclopenta-nol, and (l/ ,25)-2-(l-methyl-l-phenylethyl)cyclohexanol... 

To a solution of chiral carbene catalyst (0.03 mmol, 5 mol%) and 1-phenyletha-nol (73.2 mg, 72 pL, 0.6 mmol) in THF (2 mL) was added vinyl diphenylacetate (117.5 mg, 0.45 mmol) dropwise at —78 °C. The reaction mixture was stirred at this temperature for 3 h, and then treated with 0.1 M HCl and extracted with ether. The combined organic layers were washed with brine, dried (Na2S04), and concentrated in vacuo. The residue was purified by FC on silica gel (ether hex-anes, 1 50 to 1 2) to afford (P)-l-phenylethyl diphenylacetate (65 mg, 32%, 96% ee by chiral-HPLC) and (S)-l-phenylethanol (44.6 mg, 61%, 52% ee by chiral HPLC). The calculated selectivity value at 34% conversion was s = 80. 

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