The effect of a benzoyl peroxide-ferrocene-3,6-bis(o-carboxybenzoyl)-N-isopropylcarbazole three-component initiating system on the free-radical polymerization of methyl methacrylate has been investigated. For this process, concentration and temperature dependences of the initial rate of reaction and the average degree of polymerization have been measured. It has been established that, when the process is carried out in the presence of both ferrocene and a carbazole derivative, the former compound predominantly affects the kinetic parameters and the average degree of polymerization. The effect of the nitrogen-containing compound comes into play as the temperature of polymerization is lowered. Poly(methyl methacrylate) prepared in the presence of the ternary system is distinguished by an increased content of syndiotactic units and by the presence of isotactic structures, thus suggesting the complex-radical mechanism of polymerization.
The acetalization of phenyl 1-thio-α-L-arabinopyranoside with 2,3-butanedione in the medium of MeOH-CH(OMe) 3 -CSA proceeded with the prevailing formation of the corresponding 3,4-bisacetal that further was converted in compounds, which were regio-and stereoisomers of disaccharide block of OSW-1. O HO O SPh HO OH HO O SPh HO OAc I II IIIIn the sugar chemistry the necessity to work with awkward polyol systems makes the protective groups extremely important [1]. In the course of the planned synthesis of disaccharide block I for anticancer steroid OSW-1 based on the known components, glycosidedonor II and acceptor III [2, 3] (Scheme 1) we tested 2,3-butanedione in conditions described in [4] for the selective protection of the 3,4-diol moiety of triol II in the form of butane 2,3-bisacetal. The butane 2,3-bisacetal and the other similar protective groups introduced into the synthetic practice by Liu group [5] are known to provide a selective blocking in cycles of trans-vicinal diols, impart the products a crystalline structure, desired conformational rigidity, etc. [6].As seen from the structure of triol II all its hydroxy groups are located in the trans-equatorial reciprocal position, and here the possibility of the regiocontrolled acetalization depends mainly on the steric factors. In the experimental test of triol II acetalization by heating with excess 2,3-butanedione in the medium of MeOH-CH(OMe) 3 -camphorsulfonic acid (CSA) (catalyst) we obtained two expected acetals IV and V in the ratio ~3 : 1 and in the overall yield 80%. The main bisacetal IV is a crystalline substance easily isolated from compound V by chromatography on SiO 2 . Minor bisacetal V is oily substance containing ~10% of unidentifi ed isomeric compound. The assignment of the structure of regioisomeric acetals IV and V was carried out applying spectral data. Their 1 H NMR spectra contain a characteristic signal C 1 H which in the spectrum of 2,3-acetal V is located downfi eld (doublet, δ 4.77 ppm, J 9.6 Hz) with respect to the corresponding signal in the spectrum of compound IV (δ 4.47 ppm, d, J 9.35 Hz) because of the electron-withdrawing inductive effect of the closely Scheme 1.
ABSTRACT:The specific features of free-radical polymerization of methyl methacrylate in the presence of a new initiating system, benzoyl peroxide-N,N-dimethyl-N-(methylferrocenyl)amine, are studied. Mutual influence of ferrocenyl-and amine groups on kinetic parameters of polymerization and on the microstructure of the resulting polymers is found. It is shown that the polymer obtained in the presence of this initiating system has predominantly syndiotactic structure.
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