Cyclic Imino Ethers Research Articles

Synthesis of Polyamine Alkaloids by the Condensation of a Chiral β-Lactam with a Cyclic Imino Ether. (S)-Dihydroperiphylline and Its Derivatives

Abstract The synthesis of 13-membered polyamine alkaloid, (S)-dihydroperiphylline, was achieved by the condensation of a chiral β-lactam, (S)-4-phenyl-2-azetidinone, with a cyclic imino ether of a 9-membered lactam, followed by reductive ring expansion. Both of these reactions proceeded with retention of configuration around the chiral center to give the optical pure 13-membered alkaloids.

Synthesis, characterization and polymerization of acetylacetate, acetylacetamide or acetylacetanilide substituted cyclic imino ethers, new metal chelating monomers and polymers

New cyclic imino ether monomers, functionalized with acetylacetoxy, acetylacetamide, or acetylacetanilide moieties are described for the first time. These monomers readily form metal complexes. Also, it is shown that these monomers may be cationically homo- or copolymerized with other cyclic imino ethers, to provide polymers having metal complexing ability. The monomers have potential applications in a wide variety of applications.

Sequence control on the ring‐opening oligomerization of cyclic imino ethers

AbstractSequence‐controlled oligomers of cyclic imino ethers were synthesized by the one‐pot multi‐stage feeding method. Selective formation of the sequence was clearly demonstrated by equimolar reactions between the monomers and 1:1 adducts of an initiator with the monomers. Efficiency of the sequence control is determined by the difference of reactivities of the active ends. A new general prerequisite to synthesize a well‐defined sequence by multi‐stage oligomerization was proposed.

Alternating copolymerization of cyclic imino ethers with aryl α,β‐unsaturated carboxylates: A new method for synthesis of poly(ethyleneimine‐co‐acrylic acid)

AbstractThis paper describes an alternating copolymerization of cyclic imino ethers with aryl α,β‐unsaturated carboxylates, which occurs without added catalyst. In the combinations of 2‐methyl‐2‐oxazoline (1a) with phenyl acrylate derivatives (2a‐c), 1:1 alternating copolymers were produced. In other systems examined, 1:1 copolymers were not produced except for the combination of 2‐methyl‐5,6‐dihydro‐4H‐1,3‐oxazine (1b) with p‐cyanophenyl or p‐nitrophenyl acrylate (2b or c). The copolymerization mechanism was explained by the zwitterion intermediates. The present copolymerization let to a new synthesis of poly(ethylenamine‐co‐acrylic acid), a poly(amino acid) derivative, via the alkaline hydrolysis of the copolymer.

Ring‐opening‐closing alternating copolymerization of 2‐methyl‐2‐oxazoline with N‐methyldiacrylamide

AbstractThis paper describes a new ring‐opening‐closing alternating copolymerization (ROCAC) of 2‐methyl‐2‐oxazoline (five‐membered cyclic imino ether, 1) with N‐methyldiacrylamide (2). The reaction of a 1 : 1 monomer feed ratio proceeded without any added catalyst to give an alternating copolymer 3 having two structural units formed by ring‐opening and ring‐closing (cyclization). The structure of copolymer 3 was determined by 1H, 13C NMR, and IR spectroscopies. The extent of cyclization was at most 65%. The copolymerization was reasonably explained by a mechanism of propagation via zwitterion intermediates.

Retention of configuration in the ritter-type substitution reaction of chiral β-arylthio alcohols through the anchimeric assistance of the arylthio group

In chiral alcohols bearing a phenylthio group at the β carbon atom. the hydroxy group is replaced by nitriles through the anchimeric assistance of the phenylthio group to afford chiral amides with retention of configuration. This stereospecific Ritter-type reaction has been utilized in the conversion of chiral glycidol derivatives to chiral cyclic imino ethers such as oxazolines bearing an arylthio group.

Preparation of 2-(Perfluoroalkyl)-5,6-dihydro-4H-1,3-oxazines and Their Ring-Opening Polymerization Initiated by Sulfonates

Two monomers of 6-membered cyclic imino ethers having 2-perfluoroalkyl substituent, i.e., 2-(pentafluoroethyl)-5,6-dihydro-4H-1,3-oxazine (1a) and 2-(heptafluoropropyl)-5,6-dihydro-4H-1,3-oxazine (1b), were prepared for the first time, whose ring-opening polymerization initiated by sulfonate esters were examined. With methyl p-toluenesulfonate as initiator, the polymerization of 1 proceeded via a covalent propagating species. On the other hand, with methyl trifluoromethanesulfonate, the propagating species was of the structure of 1,3-oxazinium cation. The above mechanisms were confirmed by the in situ 1H and 19F NMR spectra of the polymerization systems as well as the isolation of the 1:1 adducts of 1 with each of the initiators. The polymerizability of 1 was discussed on the basis of the results of an equimolar reaction between the adducts and some cyclic imino ether monomers. The surface energies of the resulting polymers were evaluated by the measurement of contact angles of the polymer film against water and methylene iodide, which were found to be quite low.

Polymerization chemistry of the family of cyclic imino ethers

Characteristics of the polymerization mechanisms of the family of cyclic imino ethers are described. The variety of the mechanism of propagation has been systematized on the basis of the nature of propagating species, i.e., cationic or electrophilic covalent (dipole) species. In the polymerizations of 2-alkyl cyclic imino ethers (5- and 6-membered), propagation mechanism via one of these two different species has been established, which is dependent upon the relative nucleophilic reactivities of the monomer and the counter anion derived from initiator. The polymerization of cyclic pseudoureas having a cyclic amine substituent at 2-position proceeds in two different ways. Ionic propagation leads to the single isomerization/ring-opening polymerization involving only the cyclic imino ether ring. On the other hand, covalent propagation gives rise to the double isomerization ring-opening polymerization involving the two rings of cyclic imino ether and cyclic amine. Polymerization of 5-membered cyclic iminocarbonate with a sulfonate initiator proceeds through the isomerization/ring-opening of 2-oxazoline ring. The same monomer was isomerized to the corresponding cyclic urethane when it was treated with benzyl bromide.

Block copolymerization of vinyl ether with cyclic imino ether: synthesis of a new cleavable, nonionic polymer surfactant

Preparation par copolymerisation cationique sequentielle des n-butyl, i-octyl et n-cetyl vinyl ethers avec la 2-methyl ou la 2-ethyl-2-oxazoline. La tension superficielle minimale mesuree pour les solutions aqueuses des copolymeres ether vinylique/N-acyl ethyleneimine obtenus atteint 27,6 dyn/cm. La liaison C−N separant les sequences est facilement coupee en milieu acide pour donner les homopolymeres correspondants

Block copolymerization of tetrahydrofuran with cyclic imino ether: synthesis of a new nonionic polymer surfactant

Block copolymerization of tetrahydrofuran with cyclic imino ether: synthesis of a new nonionic polymer surfactant

Synthesis of a nonionic polymer surfactant from cyclic imino ethers by the terminator method

Synthesis of a nonionic polymer surfactant from cyclic imino ethers by the terminator method

Reactivity of cyclic imino ether salts having vinyl group

3-Methyl-2-p-styryl-2-oxazolinium trifluoromethanesulfonate (2) consisting of a polymerizable styryl group and a highly electrophilic oxazolinium ring was prepared by the N-alkylation of 2-p-styryl-2-oxazoline. The radical homo- and copolymerizations of 2 with styrene proceeded successfully. The copolymerization parameters (monomer reactivity ratio) were determined; 1.2 (for 2) and 0.25 (for styrene). This salt functions also as an initiator for the oxazoline polymerization. Poly[(N-acetyl)iminoalkylene] macromonomers with quite narrow molecular weight distributions were easily prepared by the ring-opening polymerization of 2-methyl-2-oxazoline and of 2-methyl-5,6-dihydro-4H-1, 3-oxazine by using 2 as the initiator.

Reactivity of N-alkylated cyclic imino ether salts having vinyl group

Two copolymers of 2-isopropenyl-2-oxazolinium tetrafluoroborate with methyl methacrylate and with methyl acrylate were prepared, from which the polymerization of 2-oxazolines (2-methyl and 2-t-butyl) was initiated to prepare graft copolymers.

ChemInform Abstract: Syntheses and Properties of Some Polymethylene‐Bridged Adenines.

AbstractSyntheses of novel polymethylene‐bridged derivatives (VI), (VII), (IX) of adenine are performed.

Polyaddition between 2-alkenyl cyclic imino ether and mercaptocarboxylic acid

A new polyaddition reaction between 2-alkenyl cyclic imino ether 1 and mercaptocarboxylic acid 2 was discovered. This polyaddition consists of two steps. The first reaction is the addition of a mercapto group of 2 to an activated carbon-carbon double bond of 1, which takes place at room temperature to produce the adduct 3. The second reaction is an intermolecular reaction between the carboxy group and the cyclic imino ether group with ring-opening which produces poly (amide-thioether-ester) 4.

Syntheses and properties of some polymethylene-bridged adenines

Syntheses of novel 1,2-, 2,N(6)-, and 2,9-polymethylene-bridged derivatives of adenine (7)–(9) are described. Cyclization of the intermediate 2,N(4)-bridged 4,6-diamino-5-formamidopyrimidines (6) gives a mixture of isomeric, 2,N(6)- and 2,9-bridged adenines in a ratio controlled by the number (n) of methylene groups in the chain; when n= 7, the first type (8) predominates, when n= 11, the second type (9) predominates, and when n= 9, both are formed in almost equal amounts. The structures (8) are confirmed by independent syntheses from appropriate cyclic iminoethers (2) and 5-aminoimidazole-4-carbonitrile (5) to give the 1,2-bridged adenine derivatives (7), most of which undergo spontaneous Dimroth rearrangement to afford the 2,N(6)-bridged adenines (8).

Syntheses and crosslinking reactions of self‐curable copolymers containing pendant cyclic iminoethers and carboxylic acid groups

AbstractSoluble copolymers containing both pendant cyclic iminoethers such as 4,4‐dimethyl‐2‐oxazoline or 4,4,6‐trimethyl‐4H‐dihydro‐1,3‐oxazine and carboxylic acid were successfully synthesized by radical copolymerizations of 4,4‐dimethyl‐2‐vinyl‐2‐oxazoline, 4,4‐dimethyl‐2‐isopropenyl‐2‐oxazoline, or 4,4,6‐trimethyl‐2‐vinyl‐4H‐dihydro‐1,3‐oxazine with methacrylic acid and styrene, methyl methacrylate, or ethyl acrylate using AIBN as an initiator in benzene or DMF at 60 or 80°C. The crosslinking reaction of the copolymers obtained did not occur by heating at 70°C. However, these copolymers quantitatively produced gel products by heating at 130°C. The rate of crosslinking reaction of the copolymer increased with increasing pendant cyclic iminoether and carboxylic acid groups. The rate of crosslinking was also affected by the molecular motion of the polymer chain.Our results show that the copolymers of more sterically hindered 2‐vinyl‐2‐oxazolines are more stable and so they can be crosslinked in a controlled manner and at higher temperatures than the previously studied polyoxaziline system.

Synthesis and characterization of liquid crystalline poly(N‐acylethyleneimine)s

AbstractThe synthesis of three cyclic imino ethers containing mesogenic groups attached to the heterocyclic unit through flexible spacers is described. Cationic ring‐opening isomerization polymerization of two of them, i.e., 2‐[4‐(4‐methoxy‐4′‐biphenyloxy)butyl]‐2‐oxazoline (MeOBiph‐4‐Oxz) and 2‐[6‐(4‐methoxy‐4′‐biphenyloxy)hexyl]‐2‐oxazoline (MeOBiPh‐6‐Oxz) provided thermotropic liquid crystalline (LC) poly(N‐acylethyleneimine)s, whereas the polymerization of 2‐[4‐(4‐phenylphenoxy)butyl]‐2‐oxazoline (BiPh‐4‐Oxz) led to a crystalline polymer.

Synthesis of a nonionic polymer surfactant from cyclic imino ethers by the initiator method

Preparation d'un poly(N-acyl alkyleneimine) a groupe terminal hydrophobe par polymerisation cationique de la methyl-2 et de la ethyl-2 oxazoline et de la methyl-2 dihydro-5,6 oxazine-1,3 et quenchage de l'extremite vivante avec des dimethyl-4,4 oxazoline-2 substituees en 2 par une chaine alkyl hydrophobe ou avec des amines primaires ou secondaires. Mesure des proprietes de surface des polymeres obtenus

Reactivity of Cyclic Imino Ether Salts Having Vinyl Group V. Spontaneous and Base-Catalyzed Polymerization of N-Protio Salts of 2-Alkenyl-2-oxazolines and 2-Alkenyl-5,6-dihydro-4H-1,3-oxazines

Four derivatives of 2-alkenyl cyclic imino ethers were reacted with fluorosulfonic and with trifluoromethanesulfonic acids. 2-Isopropenyl-2-oxazoline (1b) and 2-isopropenyl-5,6-dihydro-4H-1,3-oxazine (1d) formed the stable N-protonated salts at 0°C. Whereas, 2-vinyl-2-oxazoline (1a) and 2-vinyl-5,6-dihydro-4H-1,3-oxazine (1c) were polymerized on protonation (spontaneous polymerization) at the same temperature to give polymers consisting of two kinds of units; one was formed by the opening of vinyl group and the other was derived by a proton transfer. By a low temperature reaction of 1a with fluorosulfonic acid at −20°C, the N-protonated salt was successfully isolated, but the corresponding salt of 1c was not obtained by the same procedure. For these three salts isolated, base-catalyzed polymerization was examined with pyridine and triethylamine as initiators at a temperature below 20°C. The salt of 1b gave a polymer consisting exclusively of the proton transferred unit. On the contrary, the salt of 1d was not polymerized at all. As a reference salt, the N-methyl salt of 1d, i.e., 3-methyl-2-isopropenyl-5,6-dihydro-4H-1,3-oxazinium salt, was prepared by the reaction of 1d with methyl trifluoromethanesulfonate, which was not polymerized, too. On the basis of these findings the reactivity of N-methyl and N-protio salts of 2-alkenyl cyclic imino ethers were discussed.