Intramolecular cyclization polymers

Kodatra T, Liu Q-Q, Satoyama M, Urushisaki M, Utsumi H (1999) Cyclopolymerization -XXVI. Repeating unit structure of cyclopolymers derived from N-substituted-N-allyl-2-(methoxycarbonyl)allylamines and mechanism of intramolecular cyclization. Polymer 40 6947-6954, and references therein... 

M. A. Marx, A.-L. Grillot, C. T. Louer, K. A. Beaver, P. A. Bartlett, Synthetic Design for Combinatorial Chemistry. Solution and Polymer-Supported Synthesis of Polycyclic Lactams by Intramolecular Cyclization of Azo-methine Ylides , J. Am. Chem Soc. 1997,119, 6153-6167. 

When polymerizing A2B monomers there is a possibihty of losing the unique focal point due to intramolecular cyclization. The loss of the focal point in a hyperbranched polyester based on 4,4-(4 -hydroxyphenyl)pentanoic (Fig. 7) acid was closely examined by Hawker et al. [45]. The study showed no significant occurrence of intramolecular cyclization. One disadvantage of polycondensation polymers is that they are sensitive to hydrolysis, that is depolymerization, which might restrict their use. Some hyperbranched polymers are synthesized via substitution reactions which provide less hydrolytically unstable polymers. 

It is difficult to find crosslinking systems that are ideal in that all functional groups are of equal reactivity and intramolecular cyclization is negligible. The crosslinking of vinyl terminated poly(dimethylsiloxane) polymers with tri- and tetrafunctional silanes appears to be an exception. Thus the calculated and experimental pc values were 0.578 and 0.583, respectively, for the tetrafunctional silane and 0.708 and 0.703, respectively, for the trifunctional silane (with r — 0.999) [Valles and Macosko, 1979]. 

B group) units and fewer dendritic (no unreacted B groups) units. The polydispersity in molecular weight and isomerism, the intramolecular cyclization, and the molecular shape variations due to steric crowding contribute to the random nature of hyperbranched polymers. 

The importance of intramolecular cyclization was emphasized when Butler and coworkers found that the radical polymerization of N, N, N, /V-diallyldimethylammonium chloride (DADMAC) gave soluble, uncrosslinked polymers with little or no unsaturation (Eq. 6-101) [Butler and Angelo, 1957 Butler and Ingley, 1951 Wandrey et al., 1999]. There is a very low tendency for radical IV to propagate intermolecularly and undergo crosslinking. The predominant reaction is intramolecular cyclization, and the product is a linear product with cyclic structures in the backbone. The reaction is referred to as alternating intra/intermolecular polymerization or cyclopolymerization. 

Deffieux et al. have already prepared a-styrenyl-cw-acetal heterodifunctional vinylic polymers using living anionic polymerizations [26-30]. The heterotelechelic polystyrene chains containing a-hydroxy-cw-carboxy end groups using free radical polymerization were also prepared, and the intramolecular cyclization (unimolecular process) was examined [37]. The... 

A novel synthesis of a-carboxyl, co-amino heterodifunctional polystyrene and its intramolecular cyclization was reported. Cyclic polystyrene with controlled size was synthesized by the intramolecular cyclization of linear a-carboxyl, co-amino heterodifunctional polystyrene under high dilution in the presence of 2-chloro-l-methylpyridinium iodide [67]. The linear precursor polymer was derived from a-diethyl acetal, co-amino heterodifunc-... 

A cyclic polymer of methyl methacrylate was also synthesized using a het-erotelechelic polymer precursor, although the formation of living polymer of methyl methacrylate is more difficult than that of styrene. Mizawa et al. described the synthesis of heterotelechelic poly(methyl methacrylate) containing a-maleimide-tw-dienyl end groups and its intramolecular cyclization... 

Oxetanes have also been synthesized by the immobilization of 2,2 -disubstituted 1,3-diols with polymer-bound sulfonyl chloride, followed by intramolecular cyclization/cleavage from the solid support (Scheme 17) <2005TL643>. One percent divinylbenzene (DVB) cross-linked polystyrene and polyethylene glycol (PEG) (average Mn 3400) were used as polymer support in this reaction, and in both cases the properties of the polymer support allowed rapid purification of the intermediate. Intermediates on the insoluble cross-linked polystyrene support could be washed with a range of organic solvents to remove insoluble impurities, whereas the soluble PEG supported products could be purified by recrystallization from isopropanol. This is thought to represent the first reported polymer-supported synthesis of oxetanes. 

In 1994, Rubinsztajn reported the hyperbranched hydrosilylation polymerization of the AB3 carbosiloxane monomers 9 and 10181. Since intramolecular cyclization of these monomers would lead to more highly strained five-membered rings, it was expected that intermolecular reaction would be preferred. This was indeed the case, and molecular weights were highest when polymerizations were performed in bulk. Furthermore, slow addition of monomer resulted in polymers of much higher molecular weight. Functionalization of the polymers could be performed via hydrosilylation reactions, although these... 

Thus far, no successful syntheses of hyperbranched poly(carbosilazanes) have been reported. An attempt to prepare polymers of this type by hydrosilylation led to the formation of intramolecularly cyclized products in nearly quantitative yields (Scheme 27)191. 

Evans showed that his P,S-ligand 36 was also efficient for the monoalkylation of cis- 1,4-diacetoxycyclopentene 76. Reaction of dimethyl malonate/BSA gave 77 in 85% yield and 96% ee (Eq. 6) [95]. The same reaction and the intramolecular cyclization of a biscarbamate has also been reported using a polymer-supported Trost-type catalyst with excellent results [166,167]. 

The facilitation of this intrapeptide reaction has been explained on the basis of the possibility that in the rigid polymer matrix each peptide molecule is isolated from others and this would bring in the condition of infinite dilution necessary for the intramolecular cyclization (for a discussion of site-isolation in solid phase reactions see section 4.3). The method has been applied to the synthesis of several cyclic peptides in good yields. 

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