Vinyl isobutyl ether synthesis

The first synthesis of star polymers with a microgel core was reported by Sa-wamoto et al. for poly(isobutyl vinyl ether) (poly(IBVE)) [3,4]. In the first step, living cationic polymerization of IBVE was carried out with the HI/ZnI2 initiating system in toluene at -40 °C. Subsequent coupling of the living ends was performed with the various divinyl ethers 1-4. 

A new approach to /3-alkyl substituted a-methoxy vinyllithiums 540 with Z-configuration involved the stereoselective metallation of a-bromo vinyl ethers 539, prepared from acetylenes 538, with f-BuLi at — 78 °C (Scheme 145)821. These anions react with different electrophiles to give the corresponding vinyl ethers in good yields. The /3-isobutyl substituted derivative as cuprate has been added to an enone in the total synthesis of the anticancer natural product OSW-1822. 

The synthesis, starting from a bifunctional initiator followed by quenching the double-headed living ends, gives homotelechelic polymers (method B). Carboxylate-capped telechelic poly(isobutyl vinyl ether) has been obtained in this way [82], where the adduct of a bifunctional vinyl ether with trifluoroacetic acid is the initiator, and the quencher is the malonate anion. For method C, a bifunctional trimethylsilyl enol ether, CH2=C[OSi(CH3)3]C6H4OCH2CH20C6H4[(CH3)3SiO]C=CH2, is a useful terminator (chain coupler) for vinyl ethers [142,147] and a-methyl-styrene [159] (see also Section VI.B.4). 

Table 4 shows typical reaction conditions and results of the living cationic polymerization of isobutyl vinyl ether (IBVE) with the HCl/ZnCh [127] and the CFjCC H/ZnCL [227] initiating systems. The former system is now among the most convenient for the synthesis of poly(alkyl vinyl... 

Higashimura, T, Mitsuhashi, M. and Sawamoto, M. (1979) Synthesis of p-methoxystyrene-isobutyl vinyl ether block copolymers by living cationic polymerization with iodine. Macromolecules, 12, 178-183. 

The propensity of a-pyrones to undergo the Diels-Alder reaction makes them useful for syntheses of highly substituted aromatics and biphenyls. A practical method for the regioselective synthesis of the A-benzoyl-4-(polyfluoroalkyl)ani-lines 82 by thermal Diels-Alder cycloaddition of 71 with fluorostyrenes and acetylenes was described. Free 4-(polyfluoroalkyl)anilines were smoothly formed in good yields by DBU-assisted deprotection. In the case of the reactions of pyrone 71a with isobutyl vinyl ethers and cyclic vinyl ethers, compounds 83 and 84 were obtained, respectively [36] (Scheme 26). 

Liu, G.J., Hu, N.X., Xu, X.Q., and Yao, H. (1994a) Cross-linked polymer brushes. 1. Synthesis of poly[beta-(vinyloxy) ethyl cinnamate]-fo-poly(isobutyl vinyl ether). Macromolecules, 27,3892-3895. 

A formal synthesis of ( )-septicine rac-XTlT) by Padwa and his coworkers used tactics similar to those employed in their syntheses of the enzyme inhibitor (—)-A58365A (68) and ( )-lupinine (rac-926) " (cf. Schemes 6 and 125). In this route, conversion of the sulfonyl imide 1294 into the a-diazo derivative 1295 preceded reaction with rhodium(II) acetate, which generated a transient isomrinchnone intermediate that participated in a 1,3-dipolar cycloaddition with isobutyl vinyl ether to afford the substituted bicycHc pyridone 1296 in 64% yield after expulsion of... 

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