Viehe's Salt Research Articles

Synthesis and solid state structures of 1,3-dihalo-1,3-bis(dialkylamino)propenium salts and related compounds

1,3-dicholoro-1,3- bis(dialkylamino)propenium salts are prepared by condensing N, N,-dialkylamides with dichloromethylene dimethyliminium chloride (“Viehe's salt”). The products are versatile synthons and can be used to make a variety of ligand types. Here, we report the syntheses of a number of new propenium salts and provide comprehensive characterization data for some that have already been described. Additionally, we have prepared a series of related 1,3-dihalo-1,3- bis(dimethylamino)propenium salts via halogen exchange reactions (F through I). Finally, all of the compounds described, including Viehe's Salt and several hydrolysis products, have been characterized in the solid state using single crystal X-ray diffraction. The symmetrical cations [Me2NC(X)CHC(X)NMe2]+ were found to take one of two general structural forms. The first (X = H or F) is planar, presumably maximizing the delocalization within the backbone of the cation, while the second form is markedly twisted (X = Cl, Br or I). Calculations indicate that the latter develop increasingly positive regions of the electrostatic potential on the halide substituents, allowing cation/anion interactions via halogen bonding to dominate in the extended solids. The results of these studies illustrate the importance of the differing interionic interactions in a homologous series of small organic salts.

Synthesis and Characterization of Substituted Pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidines and Related Molecules

An efficient access for the synthesis of substituted pyrazino[2',3':4,5]thieno[3,2-d]pyrimidines and pyrazino[2',3':4,5]thieno[3,2-d]-1,2,3-triazines, heteroaromatic nitrogen ligands, is reported. The title compounds were obtained by functionalization of the corresponding chloro precursors, synthesized by reaction between 7-aminothieno[2,3-b]pyrazine-6-carbonitrile and N,N-dimethyldichloromethyleniminium chloride (Viehe's salt) or sodium nitrite/hydrochloric acid, respectively. Moreover, this procedure provided a convenient synthetic route to bis(pyrazino[2',3':4,5]thieno[3,2-d]pyrimidines), functionalized molecules that are not readily available by other synthetic methods.

ChemInform Abstract: A New Synthetic Approach Towards N-Alkylated 2-epi-Valienamines via Palladium-Catalyzed Coupling Reaction.

Preparation of N-alkylated 2-epi-valienamines was accomplished by the palladium-catalyzed coupling reaction of the allylic chloride 5 with various amines in the presence of trimethylolpropane phosphite (TMPP). The 2-epi-valienamine precursor (i.e. allylic chloride 5) was obtained from the reaction of diol 2 with Viehe's salt and the diol 2 was readily prepared from (−)-quinic acid in 10 steps.

A new synthetic approach towards N-alkylated 2- epi-valienamines via palladium-catalyzed coupling reaction

Preparation of N-alkylated 2- epi-valienamines was accomplished by the palladium-catalyzed coupling reaction of the allylic chloride 5 with various amines in the presence of trimethylolpropane phosphite (TMPP). The 2- epi-valienamine precursor (i.e. allylic chloride 5) was obtained from the reaction of diol 2 with Viehe's salt and the diol 2 was readily prepared from (−)-quinic acid in 10 steps.

Iminiumsalze in quantitativen Gas/Festk�per- und Festk�rper/Festk�rper-Reaktionen

Iminium Salts in Quantitative Gas/Solid and Solid/Solid Reactions Iminium salts that are highly susceptible to hydrolysis are quantitatively prepared and reacted in the solid state without solvents or liquid phases. Atomic force microscopy AFM helps in elucidating the mechanism of these still unusual gas-solid and solid-solid syntheses by recording surface topographies of reacting crystals of L-histidine (10) and triphenylverdazyl (15). Various imines add gaseous HCl or HBr to form stable iminium halides (1, 3, 4, 5, 11) even if frozen liquids of very weak heterocyclic bases are treated at low temperatures. Another way for quantitative yields of iminium salt hydrates (6) starts with solid primary ammonium halides and gaseous acetone. o-Phenylenediamines (7) give quantitatively 1,5-benzodiazepines (9) by solid state cyclization of bis-iminium salt intermediates (8). Crystalline nitroxyls (12) and triphenylverdazyl (15) undergo stoichiometric one-electron transfer with gaseous NO2 or XeF2 to give nitrosonium (14) and azonium salts (17). The solid state chlorination of tetramethylthiuramdisulfide (18) or dimethylthiocarbamoylchloride (20) yields phosgene dimethyliminiumchloride (Viehe salt 21) in quantitative yield. Solid Viehe salt is quantitatively treated with gaseous Cl2 to give the trichloride 19 and solid SbCl5 or PCl5 to produce the hexachloroantimoniates (22), -phosphates (23). Solid brenzcatechol (24), mercaptobenzimidazole (27), p-nitroaniline (30), N-methylbenzothiazolone-2-hydrazone (34) and acetophenone (41) are treated with 21 to give the corresponding chloroiminium salts (25, 28, 31, 35, 43). p-Toluenesulfonamide (37) and 22 give the chloroiminium salt 38. These quantitative solid-solid reactions are most easily run in ball mills with cooling device. The “waste-free” techniques achieve exclusion of moisture in an elegant way. The preparative use of the versatile products with nucleophiles is indicated. The three-step solid-state mechanisms are discussed.

Direct Regioselective Chlorination of Unprotected Hexitols and Pentitols by Viehe's Salt

Viehe's salt allows the transformation of unprotected hexitols and pentitols into linear 1,6 and 1,5 dichloro derivatives in high yields. Usual competitive heterocyclization is minimized.

ChemInform Abstract: Synthesis and Pharmacological Investigation of Novel Substituted Guanidines and 2‐Amino‐2‐imidazolines.

AbstractThe chloroformamidinium salts (III), prepared from the ammonium salts (I) and Viehe's salt (II), react with ethylenediamine (IV) or ammonia (VIII) to give the imidazolines (V) and (VII), the bisguanidines (VI), or the guanidines (IX).

ChemInform Abstract: The Treatment of Some Carbohydrate Alcohols and Diols with N‐Dibromomethylene‐N,N‐dialkylammonium Bromides: A Synthesis of Glycosyl Bromides.

Two analogues of Viehe's salt (Me2N+=CCl2Cl-), namely Me2N+=CBr2 Br- and Et2N+=CBr2 Br-, were prepared and treated with various carbohydrate alcohols and diols. With the diols, the products formed corresponded to those previously obtained with Viehe's salt itself, namely bromo deoxy sugars, cyclic carbonates or carbamates, and depended on the nature of the substrate and the reaction conditions. With the alcohols, mainly free sugars, a useful synthesis of glycosyl bromides was achieved.

The Treatment of Some Carbohydrate Alcohols and Diols With N-Dibromomethylene-N,N-Dialkylammonium Bromides: a Synthesis of Glycosyl Bromides

Two analogues of Viehe's salt (Me2N+=CCl2Cl-), namely Me2N+=CBr2 Br- and Et2N+=CBr2 Br-, were prepared and treated with various carbohydrate alcohols and diols. With the diols, the products formed corresponded to those previously obtained with Viehe's salt itself, namely bromo deoxy sugars, cyclic carbonates or carbamates, and depended on the nature of the substrate and the reaction conditions. With the alcohols, mainly free sugars, a useful synthesis of glycosyl bromides was achieved.

The Synthesis of Some Compounds Containing the Selenocarbonyl Group by Using Viehe's Salt/Sodium Hydrogen Selenide: an Approach to Cyclic Selenocarbonates in the Monosaccharide Series

The treatment of various thiols, phenols and amines with Viehe's salt (Me2N+=CCl2 Cl -), followed by addition to sodium hydrogen selenide in ethanol, can lead to useful syntheses of compounds containing the selenocarbonyl group, namely selenothiocarbamates, selenodithiocarbonates, selenothiocarbonates and selenoureas . As well, the combination of Viehe's salt/sodium hydrogen selenide allows the conversion of some carbohydrate cis vicinal diols into novel cyclic selenocarbonates, and a single-crystal X-ray diffraction structure determination of one of these selenocarbonates is reported. The treatment of these selenocarbonates with methyl iodide and various phosphorus reagents is reported, as well as some unsuccessful attempts towards tellurocarbonates and telluroureas.

Controlled formation of dipyranoside derivatives through C6 and O4. Pyranosidic homologation. VII

A procedure has been developed for pyranosidic homologation of methyl α-D-glucopyranoside via C4 and C6. Reaction of the aldehydo group of compound 2 with the Wittig–Bestmann reagent, Ph3P=CHCH(OEt)2, gave an E/Z mixture of acetals, 4, which cyclizes under the specific catalysis of pyridinium p-toluenesulfonate and in the presence of alcohols to give anomerically pure olefinic bipyranosides, 6a–d. A general procedure for epoxidation of the latter involves osmium tetroxide hydroxylation, followed by reaction with phosgene iminium chloride (Viehe's salt) to give chlorocarbamates 12 and 13, which are then subjected to the action of sodium methoxide. This allows for the formation of a single series of diastereomeric epoxides, 7, and controlled cleavage of the latter with nucleophiles then follows well-established precedents. Selective access to the "ends" of the bipyranosides 7c and d can be obtained by oxidative removal of the activated benzyl glycosides with DDQ.

A new synthesis of 1,2-disubstituted carbazoles. Electrophilic cyanation with Viehe's reagent.

Reaction of 2-ethylindole and 2-benzylindole with methyl vinyl ketone gives 1,2-dimethylcarbazole and 2-methyl-1-phenylcarbazole respectively. On thermolysis of the salt 11 , obtained from the reaction of 2-(2- methylpropenyl)indole ( 7a ) with Viehe's salt ( 10 ), the corresponding nitrite 13 is formed.

ChemInform Abstract: THE REACTION OF N‐(DICHLOROMETHYLENE)‐N,N‐DIMETHYLAMMONIUM CHLORIDE (VIEHE′S SALT) WITH THIOPHENOLS AND PHENOLS: A SYNTHESIS OF UNSYMMETRICAL DIARYL CARBONATES

AbstractViehes Salz (I) wird mit einer Reihe von Thiophenolen und Phenolen umgesetzt.

The reaction of N-dichloromethylene-N,N-dimethylammonium chloride (Viehe's salt) with thiophenols and phenols: a synthesis of unsymmetrical diaryl carbonates

The reaction of N-dichloromethylene-N,N-dimethylammonium chloride (Viehe's salt) with various thiophenols and phenols is reported. The resulting intermediate salts are generally transformed by water or sodium hydrogen sulfide to thiocarbonates and thiocarbamates. An efficient synthesis of unsymmetrical diaryl carbonates is discussed.

ChemInform Abstract: THE REACTION OF N‐(DICHLOROMETHYLENE)‐N,N‐DIETHYLAMMONIUM CHLORIDE WITH SOME CARBOHYDRATE ALCOHOLS AND DIOLS

AbstractDie Titelverbindung (III) ist in verbesserter Synthese ausgehend vom Aminosilan (I) zugänglich.

ChemInform Abstract: THE THERMOLYSIS OF CYCLIC IMINIUM SALTS DERIVED FROM SOME CARBOHYDRATE DIOLS AND N‐(DICHLOROMETHYLENE)‐N,N‐DIMETHYLAMMONIUM CHLORIDE (VIEHE′S SALT)

AbstractReaktion des aus dem β‐L‐Arabinosid (IIa) mit Viehe′s Salz (I) gebildeten cyclischen Iminiumsalzes (III) liefert (durch diaxiale Ringöffnung) das Chlor‐carbamat (IV) [Untersuchung und Diskussion der Konformation von (III) und der daraus sich ergebenden mechanistischen Aspekte].

ChemInform Abstract: THE CONVERSION OF SOME CARBOHYDRATE DIOLS INTO CYCLIC CARBONATES AND THIOCARBONATES BY MEANS OF N‐(DICHLOROMETHYLENE)‐N,N‐DIMETHYLAMMONIUM CHLORIDE (VIEHE′S SALT)

AbstractDie Umsetzung des Diols (II) mit Viehes Salz (I) und nachfolgende Hydrolyse bzw. Behandlung mit NaHS liefert über die Primärstufe (H13) das cyclische Carbonat (III b) bzw. Thiocarbonat (IIIc)‐.Analog werden aus den angegebenen Diolen die Verbindungen (VI), (VIII), (X) bzw. (XIIa) bzw. (XIIb) [daneben (XIb)] dargestellt.

ChemInform Abstract: THE REACTION OF N‐(DICHLOROMETHYLENE)‐N,N‐DIMETHYLAMMONIUM CHLORIDE (VIEHE′S SALT) WITH METHYL 4,6‐O‐BENZYLIDENE‐α‐D‐GLUCOSIDE. AN ALTERNATIVE SYNTHESIS OF METHYL 4,6‐O‐BENZYLIDENE‐α‐D‐ALLOSIDE

AbstractReaktion der Titelverbindungen (I) und (II) in Gegenwart von Triethylamin gibt die Carbamate (IIIa)+(IIIb); in Gegenwart von Pyridin wird dagegen als Hauptprodukt das Carbonat (IIIc) erhalten.

ChemInform Abstract: THE REACTION OF N‐(DICHLOROMETHYLENE)‐N,N‐DIMETHYLAMMONIUM CHLORIDE (VIEHE′S SALT) WITH SOME CARBOHYDRATE DIOLS

AbstractDie Reaktion der Titelverbindung (II) mit den‐ Zukkerdiolen (I) in Gegenwart von Triethylamin liefert nach Hydrolyse die Carbamate g (IIIa) bzw. (IIIb) [ + Nebenprodukt (IVb) (15%)], während in Gegenwart von Pyridin ausschließlich die Carbonate (IV) entstehen.

The reaction of N-dichloromethylene-N,N-dimethylammonium chloride (Viehe's salt) with methyl 4,6-O-benzylidene-α-D-glucoside. An alternative synthesis of methyl 4,6-O-benzylidene-α-D-alloside

The reaction of methyl 4,6-O-benzylidene-α-D-glucoside with N-dichloromethylene-N,N-dimethyl-ammonium chloride (Viehe's salt) in the presence of a base gives a mixture of carbamates (with triethylamine) or the 2,3-carbonate mainly (with pyridine). The treatment of this carbonate with various primary and secondary amines, again to give mixtures of carbamates, and an efficient synthesis of methyl 4,6-O-benzylidene-α-D-alloside from one of the gluco carbamates, are reported.