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Cyclic imino ethers

A -Imidazolines (294 Z = NH) are cyclic amidines and exhibit the characteristic resonance stabilization and high basicity. A -Oxazolines (294 Z = 0) are cyclic imino ethers, and A"-thiazolines (294 Z = S) are imino thioethers both are consequently easily hydrolyzed by dilute acid. [Pg.80]

The initial product from this reaction (100) is not observed as it undergoes spontaneous internal displacement to the cyclic imino ether salt 101. Treatment... [Pg.334]

Some particularities of the extraction of ions from an aqueous organic phase, and of the phase catalyzed polyetherification will be summarized. These will represent the fundamentals of our work on the synthesis of some novel classes of functional polymers and sequential copolymers. Examples will be provided for the synthesis of functional polymers containing only cyclic imino ethers or both cyclic imino ethers as well as their own cationic initiator attached to the same polymer backbone ABA triblock copolymers and (AB)n alternating block copolymers and a novel class of main chain thermotropic liquid crystalline polymers containing functional chain ends, i.e., polyethers. [Pg.96]

Three major topics of research which are based on phase transfer catalyzed reactions will be presented with examples. These refer to the synthesis of functional polymers containing functional groups (i.e., cyclic imino ethers) sensitive both to electrophilic and nucleophilic reagents a novel method for the preparation of regular, segmented, ABA triblock and (A-B)n alternating block copolymers, and the development of a novel class of main chain thermotropic liquid-crystalline polymers, i.e., polyethers. [Pg.99]

Functional Polymers Containing Cyclic Imino Ethers... [Pg.99]

MacrocycBc lactams. Two key steps in a synthesis of the polyamine alkaloid dihydroperiphylline (4) involve ring expansion of the cyclic imino ether 1 by reaction with the /3-lactam 2 to form 3. Sodium cyanoborohydride in acetic acid reduces 3 in high yield to 4, probably by way of intermediates a and b.2... [Pg.361]

Recently the polymerisation of cyclic imino ethers has received some attention [Ref. (154) and references therein], the most comprehensive studies being by Saegusa and his research group (125,154). Ring opening of these monomers yields poly-(N-acylalkyleneimines). [Pg.43]

Saegusa has investigated the cationic homopolymerisation of the six cyclic imino ethers shown below using methyl iodide and methyl p-toluenesulphonate as initiators. [Pg.43]

Table 11. Polymerisation of cyclic imino ethers in CD3CN at 40° C (154)... Table 11. Polymerisation of cyclic imino ethers in CD3CN at 40° C (154)...
Saegusa, T. Polymerisation of cyclic imino ethers. In Encyclopedia of polymer science and technology. Suppl. Vol 1. New York Intersdence 1976, p. 220... [Pg.278]

The first stereoselective total synthesis of AI-77B, a gastroprotective substance, was accomplished by Y. Hamada and co-workers. In the final stages of the synthetic effort, the intramolecular Pinner reaction was utilized to convert the cyano group into the corresponding carboxylic acid. The nitrile substrate was dissolved in 5% HCI in methanol, and excess trimethyl orthoformate was added at 5 °C and the reaction mixture was stirred at this temperature for almost two days. Next, the cyclic imino ether hydrochloride salt was treated with water at room temperature followed by basic hydrolysis. Finally, the pH was adjusted with HCI to obtain the natural product. [Pg.353]

C-7 Side-Chain Cleavage. 7-ACA (1), the key intermediate for the synthesis of a large number of the clinical cephalosporins, cannot be made by fermentation, nor can it be readily obtained by enzymatic removal (187) of the aminoadipic acid side chain from cephalosporin C. Because substantial quantities of 7-ACA are used, an efficient method for the chemical cleavage of the acyl side chain of cephalosporin C was sought. The first efficient method involved diazotization using nitrosyl chloride, followed by hydrolysis or alcoholysis, and gave 7-ACA in 50% yield (22,23,87,188). The reaction proceeds via the formation of the cyclic imino ether (57) which is easily hydrolyzed under very mild conditions. [Pg.33]

Weak cationating agents such as alkyl iodine, benzyl halides, and raethyl- toluenesulfonate are able to initiate the polymerization of strong nucleophilic monomers such as cyclic amines (46. 47) and cyclic imino ethers (48-52). [Pg.101]

Temporary Termination Reversible Recombination with Noncoraplex Anions. Temporary termination was evidenced for the first time in the polymerization of cyclic imino ethers (51). [Pg.108]

Grafting from is based on the use of a macromolecular initiator, that is, a polymer backbone containing dioxolenium salts as precursors of carbenium and oxocarbeniura ions (i.e., labile halides or acylhalides). The last two functional groups can be transformed into a carbenium ion by reaction with a silver salt containing a stable anion. When the monomer used is a strong nucleophile (such a cyclic imino ethers) the labile halide itself can initiate graft copolymerization. [Pg.112]

In systems devoid of chain transfer to polymer, for example, cyclic imino ethers, this method gives rise to pure block copolymers (137. 138). [Pg.114]

The above listed monomers polymerize exclusively by cationic ring-opening polymerization. Polymerization of cyclic imino ethers has been reviewed by Saegusa1,4,). In this section we follow mostly the conclusions of the Kyoto group summarizing the applied synthetic methods. Subsequently we describe initiating systems, peculiarities of chain growth, side reactions, copolymerization systems and possible applications, in this order. [Pg.209]

The polymerization of five- and six-membered cyclic imino ethers including the substituted ones, goes usually to completion (cf. Table 12-1). In addition to the relief of ring strain, the driving force of these polymerizations is the isomerization of the reactive imino ether linkages (—N=[Pg.210]

Cyclic imino ethers polymerize cationically by opening the O-alkyl bond in the onium cation, which is attacked by the most nucleophilic N-atom of the monomer in an SN2 reaction ... [Pg.210]

Table 12.2. Rate constants of polymerization of some cyclic imino ethers in CH3CN extrapolated to 35 °C, counterion OTS (CIO for 2PhOXL)... Table 12.2. Rate constants of polymerization of some cyclic imino ethers in CH3CN extrapolated to 35 °C, counterion OTS (CIO for 2PhOXL)...
Random copolymerization of different oxazolines is described in Section 15.1,2.2. The reactivity ratios increase as expected with monomer basicity 18). Statistical copolymers of cyclic imino ethers with other groups of monomers are not known, although oxazolines and oxazines form readily alternating copolymers with a number of electrophilic monomers by spontaneous zwitterionic polymerization. The mechanism and examples of this process are discussed in Section 15.2.1. [Pg.213]

This chapter will first discuss the living carbocationic polymerization of the three most important monomer classes isobutene, vinyl ethers, and styrenics. The second part of the chapter will focus on living cationic ROP of cyclic ethers, cyclic imines, and cyclic imino ethers. For more detailed discussions on carbocationic polymerizations [8-14] and cationic ROPs [15-18] in general, the readers are referred to previous literature [19]. [Pg.163]

Living cationic ring-opening polymerization (CROP) techniques represent important methods for the polymerization of a wide variety of heterocyclic monomers, such as cyclic ethers, cyclic amines, and cyclic imino ethers [7, 84-87]. The main differences between carbocationic polymerization of vinyl monomers and CROP of heterocyclic monomers arise from the nucleophilic heteroatoms... [Pg.172]

In contrast to the previously discussed cationic ROPs, the nucleophilicity of the cyclic imino ether monomers is much higher compared to the resulting poly(cyclic imino ether)s. This decrease in nucleophilicity is due to the isomerization of the imino ether moiety into an amide during the CROP as depicted in Scheme 8.25. As a result, the CROP of a wide range of cyclic imino ethers can be performed in a living manner since chain transfer to polymer side reactions are less likely to happen. Moreover, the R-group attached to the 2-position of the monomer determines the polyamide side chains and strongly influences the polymer properties. [Pg.178]

The CROP of 2-oxazoline and 2-oxazine cyclic imino ethers was first reported in 1965 by Litt in a patent application [149]. Shortly thereafter, the CROP of various... [Pg.178]


See other pages where Cyclic imino ethers is mentioned: [Pg.182]    [Pg.107]    [Pg.611]    [Pg.114]    [Pg.23]    [Pg.28]    [Pg.296]    [Pg.102]    [Pg.209]    [Pg.209]    [Pg.163]    [Pg.172]    [Pg.178]    [Pg.178]   
See also in sourсe #XX -- [ Pg.353 ]




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