Imines ring opening, direction

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

This metal-directed ring-opening of thiazolines, oxazolines and related compounds is a widespread reaction. In many cases, equilibria are set up between the heterocyclic compound and the imine. The position of these equilibria are metal-ion dependent. A typical example is seen in Fig. 5-81. The reaction of 2-(2-pyridyl)benzothiazoline (5.36) with copper(n) salts leads to the formation of complexes of the ring-opened tridentate form. 

An elaboration of this work involves the 3CR between primary a-isocyanoa-mides 67, carbonyl components 6 and primary amines 146, which could be directed towards either 2//-2-imidazolines 153 or M-(cyanomethyl)amides 156 by Ag -catalysis vs. Brpnsted acid mediated reaction, respectively (Scheme 14) [60]. The selective formation of M-(cyanomethyl)amides 156 (also earlier mentioned in the SRR approach. Scheme 7) can be rationalized by the same criteria as the formation of trisubstituted oxazoles 152 (Scheme 13), since the use of a Brpnsted acid, prevents the formation of 2-imidazolines 153 by the decreased pH. By applying a Brpnsted acid, the reaction initially proceeds via the same mechanism as for the oxazole MCR. However, when intermediate 155 is formed, it does not tautomerize to form the 5-aminooxazole 157. Instead, proton abstraction at the exocyclic imine nitrogen and subsequent ring opening gave the corresponding M-(cyanomethyl)amides 156. 

A mechanism which would reasonably explain the formation of 122 would involve the initial ring opening of the oxidation product 118, followed by hydrolysis, to give biphenyl derivative 125 via 124, which would then be reoxidized. Moreover, the formation of quinoline derivative 123 involves oxidative coupling of imine 126, derived from ammonia and propionaldehyde (120), the latter of which could be formed by direct oxidation of starting material 117, followed by dehydrogenation of 127. 

Direction of ring opening of cyclic imines 187. CHg—CHGOOLi... 

ACA is biodegraded differently than proline, which is biodegraded by an initial oxidation reaction to generate an imine and the cyclic imine is then opened hydrolytically [28]. In Pseudomonas sp. A2C, the four-membered azetidine ring of ACA undergoes direct hydrolytic opening to produce 2-hydroxy-4-aminobutyrate (Fig. 3), which is non-toxic. 2-Hydroxy-... 

The immediate product from the reaction of the hydride complex with ketone has been a subject of debate. Some have proposed that an alkoxide complex is formed and that proton transfer between the coordinated amine and the alkoxide then forms the alcohol that is ultimately released. Others have supported a direct transfer to form free alcohol (or amine) and then coordination of this species to the open To accommodate the isotope effect data and the absence of an open coordination site for coordination of the ketone, the formation of the alkoxide from the hydride has been proposed to occur by hydride transfer assisted by hydrogen bonding of the amine in the case of the reactions with [Ru(BINAP)(diamine)(H)j], or by ring slip to allow coordination of the ketone (or imine) in the case of the reactions with the Shvo catalyst. ... 

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