Vinylbenzoate

The isocoumarin 151 is prepared by the intramolecular reaction of 2-(2-propenyDbenzoic acid (149) with one equivalent of PdCbjMeCN) . However, the (Z)-phthalide 150 is obtained from the same acid with a catalytic amount of PdjOAc) under 1 atm of Oi in DMSO, alone is remarkably efficient in reoxidizing Pd(0) in DMSO. The isocoumarin 151 is obtained by the reaction of 2-(l-propenyl)benzoic acid (152) under the same conditions[4], 2-Vinylbenzoic acid (153) is also converted into the isocoumarin 154, but not to the five-membered lactone) 167,170],... 

We have noted above that benzocrowns may be nitrated quite readily. This approach was used in the formation of a photoresponsive bis-crown (see Sect. 3.8) wherein the nitrobenzo crowns reductively dimerize to the corresponding azobenzene. Kikukawa, Nagira and Matsuda have utilized 4-nitrobenzo-15-crown-5 in a somewhat different way during the synthesis of 4 -vinylbenzo-l 5-crown-5Nitration is effected using nitric acid in a mbcture of chloroform and acetic acid. 

Hydrogenation reduces the nitro group to amino which is then diazotized using sodium nitrite and tetrafluoroboric acid. The diazotized crown was not isolated but the aq. solution was treated directly with sodium acetate and bis(dibenzylideneacetone)-pal-ladium(O) in acetonitrile solution. Ethylene was then introduced to the autoclave and the solution was allowed to stir for 2 days. 4 -Vinylbenzo-15-crown-5 was isolated (30% from 4 -nitrobenzo-15-crown-5) as a colorless solid (mp 43.5—44.2°) °. The synthesis is illustrated in Eq. (3.16). 

Smid and coworkers have developed a straightforward and effective method for the synthesis of 4 -vinylbenzo-15-crown-5. In this method, 3,4-dihydroxybenzaldehyde is converted into the crown in the usual fashion and then the side chain is transformed by successive treatment with methylmagnesium bromide and then toluenesulfonic acid to effect dehydration. The overall yield is about 20%. 

For the purpose of our discussion, a polycrown is here defined as a polymer system arising by polymerization of a crown monomer unit. Extensive work has been done in this field by Kopolow, Hogen Esch and Smid and the examples presented here are taken from a paper by all three of these workers. A typical preparation of vinylbenzo-15-crown-5 is accomplished according to the scheme shown as Eq. (6.25). One might also have utilized a formylation/Wittig sequence on benzo-15-crown-5 to accomplish the same end. 

Cetyltrimethylammonium 4-vinylbenzoate (33) forms rod-like micelles that can be stabilized by radical polymerization. The resulting structure, was observed by small-angle neutron scattering to retain its original rod-like architecture and showed enhanced thermal stability and did not dissociate upon dilution. 

As vinylbenzofurans allow a large variety of substituted dibenzofurans to be synthesized, 2- and 3-vinylbenzo[b]thiophenes allow an easy entry, by Diels Alder reaction with the appropriate dienophiles, to substituted dibenzo-thiophenes which are not easily accessible by other methods. Vinylbenzo-[bjthiophenes are less reactive than the corresponding vinylbenzo[b]furans. Some cycloaddition reactions of 2-vinylbenzo[b]thiophene (82) with various dienophiles are reported [83] in Scheme 2.34. 

The 4-methoxybenzoate monooxygenase from Pseudomonas putida shows low substrate specificity. Although it introduces only a single atom of oxygen into 3-hydroxy- and 4-hydroxybenzoate, it accomplishes the conversion of 4-vinylbenzoate into the corresponding side-chain diol (Wende et al. 1989). 

Sodium 4-styrenesulfonate-5foc -sodium 4-vinylbenzoate block copolymer, 20 487 Sodium 4-vinylbenzoate, 20 469 Sodium acetate in PVA, 25 613... 

Thermal Analysis. Ito et al. have reported the effect of ester structure on ease of thermolysis and Aal-1 acidolysis of poly(p-vinylbenzoates) (//) and... 

Poly(vinylbenzo-18-crown-6) [54] dissolved in water also acts as an efficient catalyst for the decarboxylation through transfer of the substrate into the aromatic inner core of the tightly coiled polymer (Shah and Smid, 1978). The bound carboxylate decomposes 2300 times faster than in water, the rate constant (0.042 s-1) being the largest of those observed in aqueous media. 

We have recently evaluated the ATRP of a wide range of hydrophilic monomers such as 2-sulfatoethyl methacrylate (SEM), sodium 4-vinylbenzoate (NaVBA), sodium methacrylate (NaMAA), 2-(dimethylamino)ethyl methacrylate (DMA), 2-(iV-morpholino)ethyl methacrylate (MEMA), 2-(diethylamino)ethyl methacrylate (DEA), oligo(ethylene glycol) methacrylate (OEGMA), 2-hydroxyethyl methacrylate (HEMA), glycerol monomethacrylate (GMA), 2-methacryl-oyloxyethyl phosphorylcholine (MPC), and a carboxybetaine-based methacrylate [CBMA]. Their chemical structures and literature references (which contain appropriate experimental details) are summarised in Table 1. 

In principle, aqueous ATRP offers the tantalising possibility of the direct synthesis of reasonably well-defined zwitterionic block copolymers in water without recourse to protecting group chemistry. However, ATRP in acidic media is generally unprofitable, hence the (co)polymerisation of acidic monomers such as methacrylic acid or 4-vinylbenzoic acid must be carried out in weakly alkaline solution, i.e. the monomer should be in its anionic carboxylate... 

Here, HPS stands for p-(2-hydroxyisopropyl)styrene, HES for p-(l-hydroxye-thyl)styrene, 4-VPh for 4-vinyl phenol, HFS for p-(hexafluoro-2-hydroxyisopro-pyl)styrene, and 4-VBA for 4-vinylbenzoic acid. Among these, 4-VBA has the lowest pKa and the highest K2, which implies that the carboxyl group has the strongest ability to form a dimer and to liberate its proton simultaneously. Thus, we can expect that CPS forms ring-like dimers and shows miscibility and complexation features intrinsically different from PS(OH), PS(t-OH), PS(s-OH) and STVPh. 

Benzopyrrolinone-functional polymers have been prepared via polymerization of 1-vinylbenzo[c]pyrrolin-2-one (1-vinylphthalimidine) (15) (73BCJ1752) and of 5-methyl-enebenzo[c]pyrrolin-2-one (methylidinephthalimide) derivatives (16) (72MI11100). The former polymerizes readily by both free radical and cationic processes and in general displays polymerization behavior quite similar to that of l-vinylpyrrolidin-2-one (1). 

Benzo[6]furan and 2-methylbenzo[6]furan fail to undergo photooxygenation but 2,3-dimethyIbenzo[6]furan yields 2-acetoxyacetophenone (364). At -78 °C the peroxide (363) is produced which at higher temperature rearranges to the acetophenone (364 Scheme 98). 2-Vinylbenzo[6 Jfurans, e.g. trans- 2- styrylbenzo[6 Jfuran (365 Scheme 99), yield photooxides which may be isolated. Compound (366) on treatment with a catalytic amount of triethylamine yields the lactone (367) (77BCJ3026). 

Several cycloaddition reactions of vinylthiophene and vinylbenzo[6]thiophene are known. 2-Vinylthiophene easily adds 4-phenyI-l,2,4-triazoline-3,5-dione to give (308) (74JA5591). 2-Vinyl-thiophenes also undergo stereospecific cycloaddition with singlet oxygen to produce the corresponding endoperoxides (Scheme 87) (75TL4471). 

Vinylbenzo[6]thiophene is reported to form a Diels-Alder adduct with 1,4-naphthoquinone (70AHC(ll)i77>. The 3-vinyl isomer is known to be a reactive diene its cycloaddition products with maleic anhydride, p-benzoquinone, benzyne, etc. have been described. 

Vinylbenzoic acids on cyclization yield either isochroman-l-ones or phthalides or a mixture of both types. The direction of ring closure is influenced by both steric and electronic factors (62AC(R)1070). The presence of an a-substituent in the vinylbenzoic acid (621 R = Ph) leads to phthalides, whereas only isochromanones result when no such substituent is present (621 R = H Scheme 238). Ring closure presumably involves attack by the carbonyl group at the centre of lowest electron density. Thus, 2-(l-methylethenyl)benzoic acid yields the phthalide, but 2-(2-methylpropenyl)benzoic acid gives the isochroman-l-one on halolac-tonization. 

XXXIV XXXV p-Vinylbenzoe- saure-D-sek.- butylester o-Vinylbenzyl- D-sck.-butyl- sulfid CiaHi8S 204.3 206.3 Benzol kein 3,712 50 24,7 589 589 +24,0 + 13,92 ... 

Such differences were negligible in the case considered by Walden and not very high in the case of vinyl- /3-phenyIbu tyrate, para-vinyl-benzyl-sec. butylether, sec. butyl-para-vinylbenzoate and ortho-vinyl-benzyl-sec. butylsulphide prepared by Marvel (70, 72, 73), Over-berger (98) and co-workers. 

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