Immonium Salts Research Articles

ChemInform Abstract: Synthesis of Chromeno[2′,3′:4,5]imidazo[2,1‐a]isoquinolines via a Novel Domino Reaction of Isoquinoline‐Derived Immonium Salts. Scope and Limitations.

A one-pot protocol towards chromeno[2′,2′:4,5]imidazo[2,1-a]isoquinoline derivatives via a domino reaction of isoquinoline-derived immonium salts and α-hydroxy aromatic aldehydes is elaborated. The scope and limitations of this reaction is discussed.

Synthesis of chromeno[2′,3′:4,5]imidazo[2,1-a]isoquinolines via a novel domino reaction of isoquinoline-derived immonium salts. Scope and limitations

A one-pot protocol towards chromeno[2′,2′:4,5]imidazo[2,1-a]isoquinoline derivatives via a domino reaction of isoquinoline-derived immonium salts and α-hydroxy aromatic aldehydes is elaborated. The scope and limitations of this reaction is discussed.

ChemInform Abstract: A Novel Cascade Kroehnke Condensation — An Intramolecular Nucleophilic Cyclization Approach Toward Annulated Chromenes.

AbstractA simple one‐pot protocol allows the synthesis of the title compounds via a cascade reaction of immonium salts (I) and α‐hydroxyaromatic aldehydes.

ChemInform Abstract: HOBt and HOAt-Derived Immonium Salts: New and Highly Efficient Coupling Reagents for Peptide Synthesis.

Abstract Novel HOBt- and HOAt-derived immonium type coupling reagents BDMP, BPMP and AOMP were shown to be very efficient for peptide synthesis with high reactivity, low racemization and good yields. X-Ray analysis indicates BOMI exists as the N-substituted form rather than as the O-substituted form assigned previously. A mechanism for amide bond formation mediated by these reagents was proposed and studied.

A novel cascade Kröhnke condensation—an intramolecular nucleophilic cyclization approach toward annulated chromenes

Abstract A one-pot protocol toward previously unreported derivatives of chromeno[2′,2′:4,5]imidazo[2,1-a]isoquinoline via a cascade reaction of isoquinoline-derived immonium salts and α-hydroxy aromatic aldehydes is elaborated.

Microwave irradiation and COMU: a potent combination for solid-phase peptide synthesis

Here we demonstrate the compatibility of Oxyma-based uronium-type coupling reagent COMU with microwave-assisted peptide synthesizers. Consistent with previous reports, COMU displayed higher efficiency than benzotriazole classical immonium salts HATU and HBTU in the demanding synthesis of the Aib derivative of Leu-Enkephalin pentapeptide and did not yield Oxyma-based byproducts. Thus, the combination of microwave irradiation and COMU resulted in a similar performance in considerably shorter time to that achieved by manual synthesis.

Morpholine-Based Immonium and Halogenoamidinium Salts as Coupling Reagents in Peptide Synthesis1

Here we describe a new family of N-form immonium-type coupling reagents that differ in their carbocation skeleton structure. The N-methylpiperazine derivative failed to form immonium salts, while the thiomorpholine derivative did not give better results than the coupling reagents currently used. The presence of the morpholine had a marked influence on the solubility and stability as well as the reactivity of the reagent. Finally, the fluoroamidinium salt performed extremely well in the presence of only 1 equiv of base, thereby confirming the effect of the proton acceptor in the reaction.

Phototransformation products of the alkaloid lappaconitine: Multinuclear NMR study

The NMR technique has been applied to characterize the phototransformation products of the natural alkaloid lappaconitine. It was demonstrated that the photolysis of lappaconitine 1 results in cleavage of the ester bond with elimination of N-acetylanthranilic acid. The final reaction product was found to be an immonium salt 4 of N-acetylanthranilic acid and enamine 3. An equilibrium between the imine cation and the enamine 3 was detected.

Reactions of immonium and telluronium salts of 2-phenylbenzotellurazole

N-methyl-2-phenylbenzotellurazolinium iodide, like other N-methylbenzochalcogenazolium salts, readily undergoes reduction, hydrolysis, and recyclization with hydrazine hydrate and o-phenylene diamine. 1-Methyl-2-phenylbenzotelluronioazole perchlorate is an effective methylating agent in reactions with nucleophiles.

N‐Acetoxyammonium Ions – Reactive Intermediates in the Polonovski Reaction

AbstractWe have synthesized the N‐acetoxyammonium salts 5, 7, 8, 9 and 10 with different counterions (Cl–, Br–, ClO4–, BF4–, FSO3–) as models for the initially formed reactive intermediate in the Polonovski reaction. The perchlorates can be isolated in pure state. The geometries, relative stabilities and 1H and 13C chemical shifts of the N‐acetoxyammonium ions were calculated by DFT methods on the levels B3LYP/6‐311+G(2d,p) and B3LYP/TZVP. Further, the elimination reactions of the N‐acetoxyammonium salts yielding the corresponding immonium salts were studied. The immonium salts were also characterized.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Hydrothiolysis of Carbofunctional α,β‐Unsaturated Sulfides as an Approach to the Synthesis of 1,7‐Dithiocarbonyl Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Hydrothiolysis of carbofunctional α,β-unsaturated sulfides as an approach to the synthesis of 1,7-dithiocarbonyl compounds

Bis(1-N,N-dimethylimmonio-3-phenylprop-2-en-3-yl) sulfide diperchlorate and (1-N,N-dimethyl-immonio-3-phenylprop-2-en-3-yl) (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) sulfide diperchlorate react with hydrogen sulfide giving rise to the corresponding 1,7-thioxoimmonio sulfides. Treating with the hydrogen sulfide (1-N,N-dimethylimmonio-3-phenylprop-2-en-3-yl) (1-oxo-2-phenyl-inden-3-yl) sulfide perchlorate led to preparation of (1-oxo-2-phenylinden-3-yl) (1-thioxo-3-phenylprop-2-en-3-yl) sulfide. The hydrothiolysis of (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) (1-N,N-dimethylimmonio-2-phenylinden-3-yl) sulfide diperchlorate and (5,5-dimethyl-1-morpholiniocyclohex-2-en-3-yl) (1-oxo-2-phenylinden-3-yl) sulfidea perchlorate resulted in products of the sulfide bond cleavage in the initial immonium salts.

Synthesis of cationic zinc complexes from protonated diazadienes and ZnR 2 (R = Et, N(SiMe 3) 2). The crystal structures of [Pr iDADH][H 2N{B(C 6F 5) 3} 2], [{Pr iDADZn(μ-OH)} 2][H 2N{B(C 6F 5) 3} 2] 2, and [Ph*DADZnN(SiMe 3) 2][H 2N{B(C 6F 5) 3} 2

Protonation of ( MeC NC 6 H 3 Pr 2 i - 2 , 6 ) 2 (Pr i DAD) with [H(OEt 2) 2][H 2N{B(C 6F 5) 3} 2] affords the immonium salt [Pr i DADH][H 2N{B(C 6F 5) 3} 2] ( 1) which shows intra- and inter-ionic NH⋯F hydrogen bonding in the solid state. Protolysis of ZnEt 2 with [Pr i DADH][H 2N{B(C 6F 5) 3} 2] gives [(Pr i DAD)ZnEt][H 2N{B(C 6F 5) 3} 2] as a reactive intermediate. Repeated recrystallizations allowed the isolation of the dimeric zinc hydroxo complex [{(Pr i DAD)Zn(μ-OH)} 2][H 2N{B(C 6F 5) 3} 2] 2 ( 2) which shows asymmetric OH-bridges. The analogous reaction of [Ph*DADH][H 2N{B(C 6F 5) 3} 2] [Ph*DAD = (MeC NC 6H 3Ph 2-2,6) 2 with ZnMe 2 or M{N(SiMe 3) 2gives the three-coordinate Zn and Cd compounds [(Ph*DAD)ZnMe][H 2N{B(C 6F 5) 3} 2] ( 5) and [(Ph*DAD)M–N(SiMe 3) 2][H 2N{B(C 6F 5) 3} 2] ( 6, M = Zn; 7, M = Cd). The crystal structures of 1, 2 and 6 are reported.

Novel Route to N‐Alkyl‐ and N,N′‐Dialkylhydrazines by High‐Pressure Alkylation of Azines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Thiocarbonyl Compounds from β‐Substituted Vinylald‐ and ‐Ketimmonium Derivatives

AbstractFor Abstract see ChemInform Abstract in Full Text.

1,5-Hydride shift in products of Stevens 3,2-rearrangement of methyl(alkyl)(alkoxycarbonylmethyl)-(3-phenyl-2- propynyl)ammonium bromides

The products of the Stevens 3,2-rearrangement of ammonium salts containing methyl and other (ethyl, propyl, butyl) alkyl groups along with 3-phenylprop-2-ynyl, under the reaction conditions undergo, roughly by half, intramolecular hydride shift with intermediate formation of immonium salts. The latter convert into enamino esters whose hydrolysis involving alkyl groups at the nitrogen atom gives rise to lower aliphatic aldehydes and the corresponding amino esters. Treatment with dilute hydrochloric acid of the reaction mixture containing enamino esters results in formation of hydrogenated and nonhydrogenated alkyl esters of α-keto acids. This mixture was reacted with concentrated hydrochloric acid to obtain 3-hydroxy-5-methyl-4-phenylfuran-2(5H)-one from the nonhydrogenated keto ester and to isolate pure the hydrogenated keto ester.

Intramolecular 1,5‐Hydride Shift in Products of Stevens 3,2‐Rearrangement of Ammonium Salts Containing 3‐Phenyl‐2‐propynyl Group.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Direct Link Between the Passerini Reaction and α‐Lactams.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel route to N-alkyl- and N,N"-dialkylhydrazines by high-pressure alkylation of azines

Reactions of alkyl halides with azines of p-nitrobenzaldehyde, benzaldehyde, and p-methoxybenzaldehyde at a high pressure (10 kbar) were studied. Hydrolysis of the reaction mixtures gives pure N-monoalkyl- or N,N"-dialkylhydrazines in high yields, depending on the structure of the starting azine and the solvent nature. It was found that non-symmetrical N,N"-dialkylhydrazines can be synthesized without isolating intermediate N-monoquaternary immonium salts. The effect of the phase transition of the solvent on the direction of the alkylation is discussed.

A direct link between the Passerini reaction and α-lactams

α-Lactams (aziridinones) can function to replace two of the three reactants, the oxo-compound and the isonitrile, in the Passerini reaction. Four α-lactams ( 5a- d ) were reacted with mono- and dicarboxylic acids of positive p K a values to give 2-acyloxycarboxamides ( 4 ) and bis-2-acyloxycarboxamide products 12 and 13 , respectively. The same compounds were also prepared via the Passerini reaction. Acids with a negative p K a decarbonylate α-lactams to give immonium salts. The main path of the reaction depends on the p K a of the acid component, the reactivity of the α-lactam, and the reaction conditions.