Acetal iminoether

The following monomers have been classified as donors styrene [78, 79], vinyl ethers and vinyl sulphides [78], vinyl acetate [80] vinylcarbazole [81, aziridine [82], 2-oxazoline [83], 2-benzyliminotetrahydrofuran [84], five-and six-membered cyclic iminoethers, cyclic amines, cyclic phospholanes and Schifif bases [85]. Trialkoxyethylenes [86]... 

Some cyclic amines, iminoethers, sulfides, ethers, esten, and acetals were indeed demonstrated to polymerize without appreciable transfer and/or termination. It cannot be excluded that for monomers belonging to other compound classes, e.g. lactams or cyclic esters of phosphoric acid, the conditions for the transfer- and terminationless processes will be found in the near future. 

Thus, we first discuss thermodynamics, paying attention to features that are important for polymer synthesis (e.g., dependence of equilibrium monomer concentration on polymerization variables) then we describe kinetics and thermodynamics of macrocyclization, trying to combine these two related problems, usually discussed separately. In particular we present the new theory of kinetic enhancement and kinetic reduction in macrocyclics. Thereafter, we describe the polymerization of several groups of monomers, namely cyclic ethers (oxiranes, oxetanes, oxolanes, acetals, and bicyclic compounds) lactones, cyclic sulfides, cyclic amines, lactams, cyclic iminoethers, siloxanes, and cyclic phosphorus-containing compounds, in this order. We attempted to treat the chapters uniformly we discuss practical methods of synthesis of the corresponding polymers (monomer syntheses and polymer properties are added), and conditions of reaching systems state and reasons of deviations. However, for various groups of monomers the quality of the available information differ so much, that this attempt of uniformity can not be fulfilled. 

Full details have been given of the iminoether-borohydride-acetic acid method for the transformation of oxindole alkaloids into the corresponding indoles. 

Hydroxy-ester enolates are oxidized by iodine at — 78°C to give the least hindered oxiran. Thus, by generating the /3-hydroxy-ester from a ketone and acetate enolates, the overall conversion represents a stereoselective Darzens condensation. Glycidic esters can also be obtained from the corresponding nitriles via iminoether derivatives prepared by alkoxide-catalysed addition of alcohols to the nitrile group. 

For example, treatment of imino chloride 144 derived from 7p-(2-phenyl-2-bromo) acetamido-3-methyl 3-cephem benzhydryl ester (143) and phosphorus pentachloride, with an excess of methanolic lithium methoxide in THF at -78°C for 20 min, followed by quenching with acetic acid, afforded 7 -phenylketenimino-7a-methoxy- -lactam (146) in 60% yield. This material was reasonably stable to silica gel chromatography and, when treated with trifluoroacetic acid followed by aqueous quenching, quantitatively afforded 7p-phenylacetamido-7a-methoxy-3-methyl-3-cephem-4-carboxylic acid. Similar treatment of imino chlorides (144) or ketenimines (146) with lithium methoxide at -20 C provided iminoethers (147) in good yield. In the case of the imino chloride formed from 7p-dichloroacetamido-7-deacetoxycephalosporanic acid methyl ester, the corresponding iminoether (147) was obtained in 80% yield with lithium methoxide, even at — 78°C. The same imino chloride reacted... 

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