Methylene chloride derivatives, terminal

The terminal R groups can be aromatic or aliphatic. Typically, they are derivatives of monohydric phenoHc compounds including phenol and alkylated phenols, eg, /-butylphenol. In iaterfacial polymerization, bisphenol A and a monofunctional terminator are dissolved in aqueous caustic. Methylene chloride containing a phase-transfer catalyst is added. The two-phase system is stirred and phosgene is added. The bisphenol A salt reacts with the phosgene at the interface of the two solutions and the polymer "grows" into the methylene chloride. The sodium chloride by-product enters the aqueous phase. Chain length is controlled by the amount of monohydric terminator. The methylene chloride—polymer solution is separated from the aqueous brine-laden by-products. The facile separation of a pure polymer solution is the key to the interfacial process. The methylene chloride solvent is removed, and the polymer is isolated in the form of pellets, powder, or slurries. 

For N-vinylcarbazole in methylene chloride solutions cycloheptatrienyl ion has been shown to be a very efficient initiator, reacting by a rapid and direct addition to the olefin (82). A mechanistic scheme involving virtually instantaneous and quantitative initiation, rapid propagation (and transfer) and no true termination appears to operate, enabling rate constants for propagation kp, to be determined very simply from initial slopes of conversion/time curves. Under the experimental conditions used the initiators were almost totally dissociated and there seems every reason to suppose that the propagating cations are similarly dissociated (Section II.C.2). The derived rate constants therefore refer to the reactivity of free poly-(N-vinylcarbazole) cation, kp, and relevant data are summarised in Table 7. 

Methylene chloride has high solvent power for magnesium halide etherates, even those derived from terminal acetylenes, which are sparingly soluble in ether, and is recommended for use in Grignard reactions (comparable to the more expensive tetrahydrofurane).- Thus a reagent is prepared in ether as usual but the solvent is replaced by methylene chloride prior to subsequent Grignard reaction. 

Moreover, the occurrence of such a Os-H —H-N interaction on the surface of a metallic cluster has prompted us to pursue the synthesis of a novel class of terminally bound imine derivatives.[44] In fact it has been shown that the reactions of (H)( i-H)Os3(CO),o(NH3) with several aldehydes in chloroform or methylene chloride readily afford the (H)(p-H)Os3(CO),o(HN=CHR) (R = Me, Ph, CH2Ph, i-Bu) derivatives, where the stabilization of the coordinated imine is promoted by the occurrence of the unconventional hydrogen bond described above (scheme 8). 

The success achieved with phthalimidopenicillin and the knowledge accumulated in these model experiments encouraged Shionogi scientists to examine this reaction sequence with both penicillin V and G. At this point they elected to employ the known thiazoline azetidinone compound 163 which is easily prepared by the method published earlier by Cooper and Jose (1970). They reasoned that the terminal double bond in 163 was suitable for the removal of a one-carbon unit to afford the expected ozonized product. And indeed, when the bicyclic derivative (163) was ozonized in methylene chloride-methanol at -78°C followed by reduction of the ozonide with an excess of dimethyl sulfide, the desired enol ester (164) was isolated in 70% yield (see also Volume 1, Chapter 1). 

Won et al. [19], have reported synthesis of polyesters with valine, leucine, isoleucine, methionine, and phenylalanine (Table 12.1). This three-step process involves synthesis of a diester and a dinitro compound that are copolymerized [19], An amino acid is first coupled with a diol (with 3, 4, or 6 methylene groups) in the presence of tosyl to yield a diester with acid salts of diamine at the terminal ends. The second monomer, di-p-nitrophenyl ester of carboxylic acids, is synthesized by a condensation reaction of adipoyl or se-bacoyl chloride with p-nitro phenol. The final polymerization step involves an arduous condensation reaction in the presence of a strong proton abstractor between acid salt of bis(amino acid-alkyne diester) and di-p-nitrophenyl ester of dicarboxylic acids. Following along the same lines, Chu and Guo [22] have copolymerized a mixture of nitro phenyl ester of succinate, adipate, or sebacate and nitrophenyl fumarate with toluenesulfonic acid salt of phenylalanine butane-1,4-diester. The addition of fumarate derivative to the monomer mixture provides an unsaturated double bond in the polymer backbone that can be functionalized for specific biomedical... 

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