Thioiminium Salts Research Articles

Synthesis, spectral, and anti-microbial studies of thioiminium iodides and amine hydrochlorides

To avoid the undesired deprotonation during the addition of organolithium and organomagnesium reagents to ketones, the thioiminium salts, easily prepared from lactams and amides are converted into 2,2-disubstituted and 2-monosubstituted amines by reaction with simple nucleophiles such as organocerium and organocopper reagents. The reaction of thioiminium iodides with organocerium reagents derived by transmetalation of corresponding lithium reagents with anhydrous cerium(III) chloride has been investigated. These thioiminium iodides act as good electrophiles and accept alkylceriums towards bisaddition. The newly synthesized amines have been characterized by 1H and 13C NMR, IR and mass spectra. The amines have been converted into their hydrochlorides and characterized by COSY. These hydrochlorides have been subjected to antimicrobial screening with clinically isolated microorganisms, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi and Candida albicans. The hydrochlorides show quite good activity against these bacteria and fungus.

ChemInform Abstract: Thioamides and Thioformamides for Sequential Reactions with Organolithium and Grignard Reagents

AbstractReview: 41 refs.

Thioamides and Thioformamides for Sequential Reactions with Organolithium and Grignard Reagents

Abstract Sequential reactions of thioamides and thioformamides with organolithium and Grignard reagents are described. Thioiminium salts derived from these sulfur isologues of amides readily react with lithium acetylides to lead to several types of products, including α,β-unsaturated ketones, whereas sequential additions of lithium acetylides and Grignard reagents afford propargylamines. The direct addition of organolithium and Grignard reagents to thioformamides proceeds with high efficiency to give a range of tertiary amines.

Conversion of Amides into 2,2-Disubstituted Amines

2,2-Bis-alkylated cyclic amines are widely distributed scaffolds of natural biologically active compounds, as well as important pharmacophores. Thioiminium salts, readily available from lactams and amides, are found to be useful intermediates for the synthesis of this class of amines. Bis-allylation, -benzylation and -alkylation of thioiminium salts with organomagnesium and organocerium reagents proceeds at room temperature with high yields. Ring-closing metathesis of the diallylated products gives useful spiro compounds.

Sequential Addition Reaction of Lithium Acetylides and Grignard Reagents to Thioiminium Salts from Thiolactams Leading to 2,2‐Disubstituted Cyclic Amines.

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Sequential addition reaction of lithium acetylides and Grignard reagents to thioiminium salts from thiolactams leading to 2,2-disubstituted cyclic amines

Abstract The reaction of thioiminium salts derived from γ- and δ-thiolactams with lithium acetylides and Grignard reagents proceeded sequentially to give 2,2-disubstituted pyrrolidines and piperidines in moderate to high yields. In the initial step of the reaction, 2-(methylthio)pyrrolidines and -piperidines may be formed. The use of lithium (trimethylsilyl)acetylide gave the products most effectively. Aryl-, alkyl-, and allylmagnesium halides were used as Grignard reagents. Silylcarbocyclization of N -allyl 2-ethynyl cyclic amines with HSiMe 2 Ph in the presence of a catalytic amount of Rh 4 (CO) 12 was carried out to give trisubstituted hexahydro-1 H -pyrrolizines and octahydroindolizines.

Addition Reaction of Zinc Acetylides to Thioiminium Salts Leading to 3‐Amino‐1‐sulfenyl‐1,4‐enynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Addition reaction of zinc acetylides to thioiminium salts leading to 3-amino-1-sulfenyl-1,4-enynes

The reaction of thioiminium salts with zinc acetylides took place at 60 °C to give 3-amino-1-sulfenyl-1,4-enynes in moderate to good yields. Two molecules of acetylides were incorporated into the products. Nucleophilic attack of zinc acetylides to thioiminium salts may initially occur to form alkynyl S, N-acetals, followed by their [1,3]-rearrangement to give 3-sulfenyl-1-aminoallenes.

Synthesis of Tertiary Propargylamines by Sequential Reactions of in situ Generated Thioiminium Salts with Organolithium and ‐magnesium Reagents.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of tertiary propargylamines by sequential reactions of in situ generated thioiminium salts with organolithium and -magnesium reagents.

Sequential reactions of thioiminium salts generated from thioamides and methyl triflate with organolithium and -magnesium reagents proceed smoothly to give tertiary propargylamines in moderate to high yields. In all cases, two different organometallic reagents are incorporated into the starting thioamides.

Synthesis of alkyl and arylthioglycosides and thiodisaccharides via thioiminium salts in a two-phase system

A novel method was developed for the synthesis of alkyl- and arylthioglycosides and thiodisaccharides via glycosylthioiminium salt in a two-phase system using a phase transfer catalyst (PTC). Tetrabutylammonium thiocyanate and tetrabutylphosphonium bromide show a highest efficiency as a PTC for this method. In general, the phosphonium salt is more effective than the ammonium salt as a PTC, and the effect of counter anions of PTC of tetrabutylammonium type is in the order, SCN −>Br −>HSO 4 −>Cl −. The reactivity of alkyl halide RX is in the order RI>RBr>RCl, independently of the kind of PTC. Using this method, various thioglycosides were prepared in fairly good yields higher than 80%. The reactions proceed easily under mild conditions without a sulfur reagent giving an unpleasant smell.

ChemInform Abstract: Synthesis of Sulfides, Thiol Esters, and Cyclic Polythiaethers from Thioiminium Salts with a Phase‐Transfer Catalyst

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Umpolung of reactivity at the C-5 position of uracil: 1,2 facile nucleophilic reactions of thiolate ions at C-5 of 6-cyano-1,3-dimethyluracil to procure 5-alkyl or 5-aryl-thio-1,3-dimethyluracils

1,3-Dimethyluracil-6-carbonitrile 1 with thiolate ions generated in situ from thioiminium salts or thiols under phase transfer catalytic conditions undergoes umpolung of reactivity at C-5 to give 5-alkyl- or 5-aryl-thio-l,3-dimethyluracils as the major or sole products. However, propane-1,3-dithiol causes reductive decyanation of 1 to 1,3-dimethyluracil.

ChemInform Abstract: Carboxyl‐Modified Amino Acids and Peptides. Part 2. A Convenient Route for the Synthesis of Difunctionalized Enamines from Thioamides via Thioiminium Salts.

ChemInform Abstract: Carboxyl‐Modified Amino Acids and Peptides. Part 2. A Convenient Route for the Synthesis of Difunctionalized Enamines from Thioamides via Thioiminium Salts.

ChemInform Abstract: Carboxyl‐Modified Amino Acids and Peptides. Part 1. An Efficient Method for the Synthesis of Monofunctionalized Enamines and Monofunctionalized Methyl Ketone Derivatives from Thioamides via Episulfides and Thioiminium Salts.

ChemInform Abstract: Carboxyl‐Modified Amino Acids and Peptides. Part 1. An Efficient Method for the Synthesis of Monofunctionalized Enamines and Monofunctionalized Methyl Ketone Derivatives from Thioamides via Episulfides and Thioiminium Salts.

Carboxyl-modified amino acids and peptides: II) A convenient route for the synthesis of difunctionalized enamines from thioamides via thioiminium salts

From thioamides 4, via thioiminium salts 5, various difunctionalized enamines 6 with different electron-withdrawing groups E, E′ (E: CN, CO 2Me, COR, SO 2R, etc; E′: CN, CO 2Me) are prepared. Application of the methodology, the determination of stereochemistry and the degree of racemization of some amino acids are discussed.

Carboxyl-modified amino acids and peptides: I) An efficient method for the synthesis of monofunctionalized enamines and monofunctionalized methyl ketone derivatives from thioamides via episulfides and thioiminium salts

Thioamides 4 were transformed by two convenient routes to various functionalized enamines 7 containing different electron-withdrawing groups E which on subsequent hydrolysis gave the corresponding methyl ketone derivatives 8. Application of this methodology to obtain modified dipeptides at the carboxyl end, the determination of stereochemistry and the degree of racemization are discussed.

Lithio-ketene-S,N-acetals: New Synthesis of Multifunctionalized 2-Pyridones

Lithioketene-S,N-acetal derived from N,N-dimethylthioacetamide reacts with aryl isocyanates to give monothiodiamides, which ware transformed into enaminonitriles by sulfide extrusion of the thioiminium salts with malononitrile. Bislithioketene-O,N-acetals, generated from the enaminonitriles with 2 equivalents n-butyllithium, react with a variety of electrophiles to afford multifunctionalized 2-pyridones.

A Conventent Synthesis of Functonalised Heterocuclic Enamines from Alpha-Thioiminium Salts and Active Methylene Compounds Under Solid-Liquid PTC Conditions

Abstract Functionalised enanines constitute a category of synthetic intermediates useful in carbon, carbon bond formation reactions and have been procured through a variety of condensaticn and extrusion reactions.1 In one approach active methylene compounds have been condensed with lactin thioethers in the presence of a base at relatively higher temperature.2,3 In view of our interest in the synthesis of function alised enamines through sulphur extrusion reactions4, we have studied the title reaction under non-hydrolytic solid-liquid PTC using solid KF(base)/TEBA(catalyst). A recent report5 on the sulphur extrusion of α -thio-iminium salts and their reactions with active methylene compounds prompts us to report our results.