Bis ammonium salts

More recently, Johnson and Sutherland have used bridged monoazacrowns as host molecules for bis-ammonium salts. The intramolecular bis-crown diammonium complex formed when the size relationships are appropriate is shown below as structure 8. 

The nitrogen atom in quinolizidine derivatives behaves as a tertiary amine and hence it can undergo quaternization by reaction with alkyl halides. For instance, berberine derivative 101 was transformed into 102 by treatment with 3-iodopropanol followed by anion exchange. Compound 102 was then transformed into intermediate 103, which was employed as a precursor for the the preparation of bis-ammonium salt 104 (Scheme 10). This compound showed ultrashort curare-like activity in rhesus monkeys <2001JOC3495>. 

Particularly rapid are the quantitative salt formations of gaseous ammonia with 2-furancarboxylic (24), 2-furylacrylic (25), and 3,4-furandicarboxylic acid (26), and maleic (27) or fumaric acid (28) (bis-ammonium salts) (Scheme 3). Applications in removal of ammonia from atmospheric gases appear promising [22,28]. 

Moreover, one of the chiral bis-ammonium salts (i.e., 44b) was used to determine the enantiomeric excess of three mixtures of Mosher s acids by NMR spectroscopy. 

Undecaprenyl monophosphate bis-ammonium salt may be purchased from Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5A, 02-106 Warszawa, Poland. 

Arai et al. also reported another BINOL-derived two-center phase-transfer catalyst 31 for an asymmetric Michael reaction (Scheme 6.11) [8b]. Based on the fact that BINOL and its derivatives are versatile chiral catalysts, and that bis-ammonium salts are expected to accelerate the reaction due to the two reaction sites - thus preventing an undesired reaction pathway - catalyst 31 was designed and synthesized from the di-MOM ether of (S)-BINOL in six steps. After optimization of the reaction conditions, the use of 1 mol% of catalyst 31a promoted the asymmetric Michael reaction of glycine Schiff base 8 to various Michael acceptors, with up to 75% ee. When catalyst 31b or 31c was used as a catalyst, a lower chemical yield and selectivity were obtained, indicating the importance of the interaction between tt-electrons of the aromatic rings in the catalyst and substrate. In addition, the amine moiety in catalyst 31 had an important role in enantioselectivity (34d and 34e lower yield and selectivity), while catalyst 31a gave the best results. 

Gibson et al. recently demonstrated that a pseudorotaxane-like linear assembly can be synthesized from a bis crown ether moiety and a bis ammonium salt... 

Molecular boxes , capable of binding a decanediyldiammonium or dodecanediyl-diammonium ion in their cavities, have been constructed from diazacrown ethers and pendant nucleotide bases. ° For example, structure 25 is based on hydrogen-bonded adenine-diazacrown-adenine and thymine-diazacrown-thiamine monomer units. The bis(ammonium) salt interacts with the oxygen atoms of two azacrown rings contained in each half of the cyclic 1 1 host-guest box . Characterisation of this product was largely performed using H-NMR spectroscopy and vapour... 

The simplest of the diazirines, diazirine itself, has now been obtained by a number of different routes. Perhaps the most convenient prepa ration is from a methylene-bis-ammonium salt by reaction with hypochlorite. Diazirine is a colorless gas, b.p. — 14°C. It is explosive and should always be handled with caution. Schmitz reported that it... 

Triple bonds have been prepared by pyrolysis of l,2-bis(ammonium) salts. ... 

Finally, convergent peptide synthesis imder homogeneous conditions has been demonstrated two supported peptides prepared by inverse and direct peptide synthesis have been successfully coupled to obtain a supported hexapeptide as a bis-ammonium salt (Scheme 5.5-48) [50]. 

In this context, there is a relevant example of a newly designed cinchona-alkaloid derived bis-ammonium salt 105 employed as catalyst in the Michael reaction of cyclic p-ketoesters with methyl vinyl ketone (Scheme 5.12). Excellent yields and moderate enantioselectivities of the corresponding Michael adducts were obtained under the best reaction conditions, which also allowed the use of an organic base (Hiinig base) for the deprotonation of the p-ketoester. However, perhaps the most relevant feature associated to the use of this catalyst is the fact that it can be easily separated from the reaction medium by precipitation in ether, which allowed its recycling for further uses without loss of activity. 

Finally, it should also be pointed out that the dimeric quinidine-based bis-ammonium salt 105 developed by Najera has also been shown to perform quite well in the reaction of cyclic p-ketoesters with acrolein, furnishing the corresponding adducts in good yields and enantioselectivities (Seheme 5.30). As was pointed out earlier, one of the main advantages associated with the use of this catalyst is the possibility of its recycling for further uses in other reaetions without loss of activity after precipitation with diethyl ether. 

Furthering this work, Denmark produced a range of 0x0 bis(ammonium) salts to enhance the electrophilicity of the carbonyl carbon and it was hoped this would eliminate the Baeyer-Villiger reaction. The first two attempts resulted in no formation of epoxide in the oxidation reaction. Oxone decomposition studies revealed that the catalysts were rapidly destroyed by oxone. 

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