O-Methoxystyrene

Fig. 10. Influence of the initiator concentration on the rate of polymerization of o-methoxystyrene. (J. Geerts, M. Van Beylen, G. Smets, Ref. 69))...

This procedure has been used in the preparation of other nitrostyrenes in the following yields o-nitrostyrene (40%),2 / -nitrostyrene (41%),2 and 3-nitro-4-hydroxystyrene (60%).2 A better procedure for more volatile styrenes involves simultaneous decarboxylation and codistillation with quinoline from the reaction flask. This method has been used to prepare the following styrenes o-chlorostyrene (50%),3 4 m-chlorostyrene (65%),4 -chlorostyrene (51%),4 m-bromostyrene (47%),4 o-methoxystyrene (40%),4 -methoxystyrene (76%),4 m-cyano-styrene (51%),3 and j -formylstyrene (52%).9... 

A potentially valuable contribution to our understanding of the generality of a connection between the order of the propagation and active center concentration could have come from the study 164 of the polymerization of o-methoxystyrene in... 

The solvation of ion pairs may also arise from intramolecular interaction. For example, the high reactivity of living poly(2-vinylpyridine) is probably caused by the intramolecular solvation of the Na+ ion by the adjacent pyridine rings (16, 23, 32). Interesting example of such a solvation has been discovered by Smets and van Beylen (30), who studied anionic polymerization of p- and o-methoxystyrene. The ion pair of the latter living polymer, but not of the former, showed exceptional reactivity, and the model reveals that only the o-methoxy group can participate in the intramolecular solvation. 

With o-methoxystyrene, the presence of the methoxy group appears to... 

The presence of heteroatoms like oxygen or nitrogen in the monomer causes rapid complexation with the organometallic compounds. For instance, when butyllithium initiates polymerization of styrene in hydrocarbon solvents, there is an induction period and the overall reaction is slow and sluggish. When, however, it initiates polymerization of o-methoxystyrene under the same conditions, there is no induction period and the reaction is rapid. This is due to the initiator coordinating with the oxygen atom... 

Fenoldopam (76) is an antihypertensive renal vasodilator apparently operating through the dopamine system. It is conceptually similar to trepipam. Fenoldopam is superior to dopamine itself because of its oral activity and selectivity for dopamine D-1 receptors (D-2 receptors are as.sociated with emesis). It is synthesized by reduction of 3,4-dimethoxyphenylacetonitrile (70) to dimethoxyphenethylamine (71). Attack of diis last on 4-methoxystyrene oxide (72) leads to the product of attack on the epoxide on the less hindered side (73). Ring closure with strong acid leads to substituted benzazepine 74. O-Dealkylation is accomplished with boron tribromide and the catechol moiety is oxidized to the ortho-quinone 75. Treatment with 9NHC1 results in conjugate (1,6) chloride addition and the formation of fenoldopam (76) [20,21]. 

A total synthesis of O-methylarnottianamide (223) was performed by Falck et al. (177) (Scheme 34). The regio- and stereospecific cycloaddition of the 2,4-dinitrophenyl (DNP) salt of 6,7-methylenedioxyisoquinoline (218) with a-methoxystyrene 219 resulted in 220. Compound 220 was hydrolyzed, then aromatized, and the resultant aldehyde was oxidized to carboxylic acid 221. Curtius rearrangement of the appropriate azide yielded urethane 222, which... 

For the polymerisation of styrene (SnC -F O-PhNC -CC at 0°) kjkv for anisole was found [85] to be 1.62. It is highly probable that the big difference between this and the value for isobutene reflects mainly the difference between the ps for the two monomers. The very low value of kjkv in the polymerisation of isobutene - or the very large kv of isobutene - accounts for the observation [86] that, whereas styrene polymerising cationically in the presence of preformed poly-p-methoxystyrene will form grafts by reacting with pendent rings, isobutene will not do so. 

In the case of p-methoxystyrene (p-MeOCgH4CH=CH2), the cation-radical ring closure can lead to 1,2-dianisylcyclobntane or 4-anisyl-6-methoxy-3,4-dihydronaphthalene. Thermodynamic simulations show that the former should be favored in the absence of a solvent, whereas the latter product could be stabilized by a polar solvent (O Neil and Wiest 2006). Of course, such a solvent has to be fairly polar and not nncleophilic. 

Fig. 6. Variation of degree of polymerization with monomer concentration p-methoxystyrene-iodine-l,2-dichloroethane [lj]0 = 1.0 X 10 1 mole/1. 1.5 KV/cm O 0 KV/cm. Reproduced, with permission, from Sakurada, Ise, and Ashida Makromol. Chem. 95, I (1966)...

Probably the most rewarding experiments involving stable carbocation salts have been those using the monomers alkyl vinyl ethers (79-81X N-vinylcarbazole (82), p-methoxystyrene (21,67), cyclopentadiene (86), o-divinylbenzene (92), and to a lesser extent indene (34). 

The simpler system /3-methoxystyrene (1) has now been examined (equation II). Both the cis- and tranr-isomers of 1 also give the unstable endoperoxides 2, which lose methanol to form the o-formylmethide quinone 3. 

Initiations of polymerizations of vinyl and other monomers by metal alkyls generally take place by anionic mechanisms. This is discussed further in this chapter. There are, however, reports in the literature of cationic polymerizations that are initiated by some metal alkyls. These are polymerizations of monomers like vinyl ethers, o- and p-methoxystyrene, and isobutylene " that are initiated by compounds like dialkyl aluminum chloride. 

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