In this systematic study six new chiral alkali-metal complexes derived from (S)-α-(methylbenzyl)benzylamine (αmmba) have been synthesized and characterized in the solution state, with five successfully analyzed by single-crystal X-ray diffraction. The reaction products observed are highly dependent on the choice of alkali metal and Lewis donor used, affording either the amido deprotonation complex [Li{PhCH(Me)NCH 2 Ph}•HMPA] 2 (3) when using nBuLi or the aza-allyl complexes [Na{PhC(Me)NCHPh}•TMEDA] ∞ (4), [Na{PhC(Me)NCHPh}•3THF] (5), [Na{PhC(Me)NCHPh}•THF•TMEDA] (6), and [K{PhC(Me)NCHPh}•PMDETA] ∞ (8) via hydrogen elimination reactions. Unexpectedly a co-secondary product is also obtained when tridentate or pseudo-tridentate donor ligands are used in the reaction of α-mbba with either nBuNa or nBuK to give the unexpected 1, 3-diphenyl-2-aza-allyl complexes[M{(PhCH) 2 N}•L] [M = Na, L = 3 THF (5a) or TMEDA/THF (6a); M = K, L = PMDETA (8a)] in various ratios. Reinforcing the experimental findings, formation of the methane elimination complex was confirmed via GC-headspace analysis experiments, while theoretical DTF calculations on model systems reinforce the experimental findings showing that thermodynamic gas elimination pathways trend toward the larger alkali metals with H 2 elimination kinetically favored over CH 4 .
Eight bismuth(III) complexes derived from a variety of α-amino acids covering a range of physico-chemical properties (L-phenylalanine (Phe), L-proline (Pro), L-methionine (Met), L-cysteine (Cys), D,L-serine (Ser), L-tyrosine (Tyr), l-aspartic acid (Asp) and L-glutamic acid (Glu)) have been synthesised, characterised, and evaluated for their activity against Helicobacter pylori. The optimal synthetic procedure utilises [Bi(O(t)Bu)3], giving the complexes [BiL3] (L = Phe 1, Pro 2, Met 3, Ser 5, Tyr 6) and [Bi2L3] (L = Cys 4, Asp 7, Glu 8) cleanly and in good yield. However, the synthesis is sensitive to both temperature and moisture. The solubility and stability of the bismuth(III) complexes was investigated using ESI-MS. Almost all compounds (except for [Bi(Phe)3] and [Bi(Pro)3]) were found to be partially or completely soluble in aqueous solution giving a pH 2.5-5.0, indicating the presence of free α-amino acid and hydrolysis of the bismuth(III) complexes to polynuclear bismuth oxido-clusters. The results of the bactericidal studies against Helicobacter pylori demonstrate that this hydrolysis process impacts significantly on the observed Minimum Inhibitory Concentration (MICs) which are increased substantially, often by many orders of magnitude, when the complexes are initially prepared in water rather than DMSO.
An
unexpected aza-enolate propyl addition complex, [(PhCCH2)(CHC(CH2CH2CH3)CH3)NNa·THF]∞ (1), was isolated
when (S)-N-α-(methylbenzyl)allylamine
reacted in hexane with nBuNa in the presence of THF.
Analytical studies revealed a decomposition of the sodium 1-azaallylamide
to a sodium enamide and propene, identified by solution studies and
a GC-headspace study, respectively. Propene then adds to the carbanion
tautomer of the sodium 1-azaallylamide followed by anionic rearrangements
to later form the aza-enolate propyl addition complex.
A large variety of aryl and heterocyclic chiral and achiral imines can be generated simply, efficiently, and cleanly through the use of microwave irradiation and the use of a small amount of molecular sieve. Reactions are rapid and complete in a matter of minutes, and can be quantitative, reducing significantly the time and amount of solvents used in compound isolation and purification.OMe O ϩ H Scheme 2. The microwave synthesis of 1a, 1b, and 1c.
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