Georg Ziegler

New Formylating Agents − Preparative Procedures and Mechanistic Investigations

The reactivity of new formylating agents related to formamide has been investigated both experimentally and theoretically. The reaction in 1,2-dichloroethane between tris(diformylamino)methane (2) and several arenes, catalyzed by AlCl3 or BCl3, was shown to proceed in good yields to afford the corresponding para-substituted aldehydes. The nature of the active electrophilic species was also investigated theoretically. Thus, the relative stability of the O- and N-protonated forms, as well as those of AlCl3 adducts, of several formylating agents − diformamide, triformamide, N,N,N′,N′-tetraformylhydrazine, and tris(diformylamino)methane − were determined in the gas phase and in water or DCE by means of DFT calculations at the B3LYP/6-311++G(d,p) level, the solvents being modeled with the IPCM method. The amide oxygen atom in all cases appeared to be the most basic site, both in the Bronsted and Lewis sense, constituting a first step towards the understanding of the mechanism of this reaction.

Eine neue, breit anwendbare Synthese für aromatische Aldehyde

Diformamide (1) reacts with activated aromatic compounds like toluene, anisole, m-xylene, 1,2-dimethoxybenzene in the presence of AlCl3 to give N-(diarylmethyl)-formamides 2a—d, the corresponding aromatic aldehydes 3—6 are formed as by-products in low yields. From N,N-dimethylaniline and 1/AlCl3 the triphenylmethane derivative 7 can be obtained. The reaction of anisole with N-methyl-diformamide (9) affords the formamide 10. The mixture of formamide, P4O10 and AlCl3 reveals to be a reagent which is capable to formylate toluene and anisole, resp. Triformamide (14)/AlCl3 is an effective formylating system which allows the preparation of aromatic aldehydes (e.g.3,4,17—32) from the corresponding aromatic hydrocarbons. Aluminiumchloride can be replaced by borontrichloride. The yields of the formylation reactions depend strongly from the reaction conditions (molar ratio: aromatic hydrocarbon/AlCl3/14; solvent, reaction temperature). The scope of the reaction covers nearly complete those of the Gattermann-Koch-, Gattermann- and Vilsmeier—Haack-reaction.

Orthoamide, LXIII [1]. Tris(dichlormethyl)amin, ein neues breit anwendbares Formylierungsmittel für Aromaten / Orthoamides, LXIII [1]. Tris(dichloromethyl)amine, a New Formylating Reagent for Aromatic Compounds of Wide Scope

The reagent system formed from tris(dichloromethyl)amine (5) and aluminium chloride allows the formylation of aromatic compounds. The scope of the method is comparable with that of the Olah formylation and the Groß-Rieche procedure, since benzene and even chlorobenzene can be formylated. One formyl group is transferred from 5 to the aromatic nucleus. In order to find optimal reaction conditions, the molar amounts of aromatic compounds, 5 and aluminum chloride were varied as well as reaction temperatures and solvents. The activation of 5 with other Lewis acids is also described

Orthoamide, LVII [1]. Lassen sich aromatische Aldehyde nach Fries aus Arylformiaten hersteilen? / Orthoamides, LVII [1]. Can Aromatic Aldehydes be Prepared from Aryl Formates via the Fries Rearrangement?

The aromatic hydroxyaldehydes 3a-3g, 5a-5f, 8 , 10 can be prepared by the action of BCl3, BBr3 or trifluoromethanesulfonic acid, on the aryl formates 1a-1f, 4a-e, 7, 9 via Fries rearrangement. BBr3 is more effective than BCl3. The activating ability of BBr3 can be improved by addition of FeCl3. Rearrangements which are induced by trifluoromethanesulfonic acid can give rise to the formations of regioisomers, which might be different from the products formed when the reaction is performed with Lewis acids. The yields of the aldehydes are lowered by subsequent condensation reactions. This view was confirmed by the isolation of a condensation product, which was characterized as a dibenzo[a,j]xanthene derivative 6 by crystal structure analysis. For the Fries rearrangement of formyl groups a new mechanism is proposed. 2-Hydroxy-1-naphthaldehyde 5c can be obtained in good yield from formic acid, BBr3, and 2 -naphthol.

Orthoamide und Iminiumsalze, LXXXVIII. Synthese N,N,N′,N′,N″,N″-persubstituierter Guanidiniumsalze aus N,N′-persubstituierten Harnstoff/Säurechlorid-Addukten**

Abstract N,N,N′,N′,N″,N″-Hexamethylguanidinium chloride 9c was prepared by treating the reaction mixture formed from N,N,N′,N′-tetramethylurea (1a) and phthaloyl chloride (16) with dimethyltrimethylsilylamine 15. N,N,N′,N′-Tetramethyl-chloroformamidinium chloride (2a) is an intermediate in this synthesis. The chloroformamidinium chloride 2a can also be prepared by treating the urea 1a with thionyl chloride or phosphorus pentachloride, respectively. The guanidinium salt 9c can be obtained from the crude 2a thus prepared and the silylamine 15. From urea/phosphoryl chloride adducts and primary aromatic amines have been prepared guanidines 38, which are converted to N,N′-diaryl-N,N′,N″,N″-tetramethyl-guanidinium iodides 39 on treatment with methyl iodide. The N,N′,N″-trimethyl-N,N′,N″-triphenylguanidinium salt 44a was prepared from the chloroformamidinium salt 43 and N-methylaniline. The guanidinium salt 9c is the reaction product when the urea 1a/POCl3 adduct is treated with the silylamine 15.

Orthoamide und Iminiumsalze, LXXXIV [1]. Die Synthese von starken Formylierungsmitteln im präparativen Großmaßstab: Tris(dichlormethyl)amin / Orthoamides and Iminiumsalts LXXXIV [1]. The Synthesis of Strong Formylating Reagents on a Large Preparative Scale: Tris(chloromethyl)amine

Tris(chloromethyl)amine (4) can be prepared by chloromethylation of urotropin with paraformaldehyde or 1,3,5-trioxane and ethyl-trichlorosilane in good yields. Photochlorination of tris(chloromethyl)amine affords tris(dichloromethyl)amine (2). Both reactions can be performed on large scale. Graphical Abstract Orthoamide und Iminiumsalze, LXXXIV [1]. Die Synthese von starken Formylierungsmitteln im präparativen Großmaßstab: Tris(dichlormethyl)amin / Orthoamides and Iminiumsalts LXXXIV [1]. The Synthesis of Strong Formylating Reagents on a Large Preparative Scale: Tris(chloromethyl)amine

Orthoamide und Iminiumsalze, LXXXIII [1]. Die Synthese von starken Formylierungsmitteln im präparativen Großmaßstab: Triformamid (Triformylamin) / Orthoamides and Iminium Salts LXXXIII [1]. The Synthesis of Strong Formylating Reagents on Large Preparative Scale: Triformamide (Triformylamine)

The preparation of sodium diformamide (7) from formamide and sodium methanolate under azeotropic removal of methanol with cyclohexane, or from formamide and sodium ethanolate in ethanol, is described. Diformamide (8) can be prepared by treatment of sodium diformamide (7) with formic acid. Triformamide (triformylamine) (1) is formed in the reaction of sodium diformamide with inorganic acid halides such as SOCl2, SO2Cl2 or PCl3 in acetonitrile at low temperatures. Triformamide (1) can be prepared on a large scale by the action of methanesulfonyl chloride on finely powdered sodium diformamide (7) in acetonitrile. Tris(diformylamino)methane (4) can be formed as a side product. A procedure was developed for the large-scale preparation of N;N-diformylacetamide (6) from sodium diformamide and acetyl chloride. Triformamide (1) can be prepared from N;Ndiformylacetamide (6) and diformamide with good yields Graphical Abstract Orthoamide und Iminiumsalze, LXXXIII [1]. Die Synthese von starken Formylierungsmitteln im präparativen Großmaßstab: Triformamid (Triformylamin) / Orthoamides and Iminium Salts LXXXIII [1]. The Synthesis of Strong Formylating Reagents on Large Preparative Scale: Triformamide (Triformylamine)

Orthoamide, LXIX [1]. Beiträge zur Synthese N,N,N´,N´,N´´-peralkylierter Guanidine und N,N,N´,N´,N´´䞲,N´´-persubstituierter Guanidiniumsalze / Orthoamides, LXIX [1]. Contributions to the Synthesis of N, N, N´, N´, N´-peralkylated Guanidines and N, N, N´, N´, N´´, N´´-persubstituted Guanidinium Salts

N, N, N´, N´-Tetraalkyl-chloroformamidinium chlorides 6 are prepared from N, N, N´, N´-tetraalkylureas 5 and phosgene in acetonitrile. The iminium salts 6 react with primary and secondary amines in the presence of triethylamine to give N, N, N´, N´, N´´-pentasubstituted and N, N, N´, N´, N´´, N´´- hexasubstituted guanidinium salts 7 and 8, respectively, Treatment of the guanidinium salts 7 with sodium hydroxide in excess affords the N, N, N´N´, N´´-pentasubstituted guanidines 9a - 9aa. Additionally, the N, N, N´, N´, N´´-pentasubstituted and N, N, N´, N´, N´´, N´´-hexasubstituted guanidinium salts 7l´, 7p´ and 8a - c can be obtained from the reaction mixtures by addition of stoichiometric amounts of sodium hydroxide. A modified method is described for the preparation of guanidinium salts possessing dialkylamino substituents consisting of two long-chain alkyl groups (>C14). Some guanidines 9 were alkylated with allyl chloride and bromide, ethyl bromide, butyl bromide, benzyl bromide and chloride, dimethyl sulfate, diethyl sulfate, and methyl methansulfonate to give the corresponding guanidinium salts 11 - 15. By alkylation of the N, N, N´, N´, N´´-pentasubstituted guanidine 9v with triethyloxonium tetrafluoroborate the guandinium tetrafluoroborate 16a is accessible. N-Functionalized guanidinium salts 17 - 18a - c result from the reaction of N, N, N´, N´, N´´-pentasubstituted guanidines with ethyl bromoacetate and bromoacetonitrile, respectively, and subsequent anion exchange with sodium tetraphenylborate. N, N, N´, N´-Tetramethylguanidine (21) adds to ethyl acrylate to give the labile guanidine 22, which forms the guanidinium salt 23a on treatment with methyl iodide. Zwitterionic guanidinium salts 25 result, when N, N, N´, N´, N´´-pentasubstituted guanidines are treated with sultones 24. Graphical Abstract Orthoamide, LXIX [1]. Beiträge zur Synthese N,N,N´,N´,N´´-peralkylierter Guanidine und N,N,N´,N´,N´´䞲,N´´-persubstituierter Guanidiniumsalze / Orthoamides, LXIX [1]. Contributions to the Synthesis of N, N, N´, N´, N´-peralkylated Guanidines and N, N, N´, N´, N´´, N´´-persubstituted Guanidinium Salts

Orthoamide, LXIV [1]. Aromatenformylierungen mit Tris(dichlormethyl)amin und Oligoformylamin-Derivaten in Gegenwart von Supersäuren / Orthoamides, LXIV [1]. Formylation of Aromatic Compounds by Tris(dichloromethyl)amine and Oligoformylamine Derivatives in the Presence of Superacids

Tris(dichloromethyl)amine (4), triformamide (1) and tris(diformylamino)methane (“formylaalen”) (2) can be activated by addition of trifluoromethanesulfonic acid. The formylating systems thus formed transform activated aromatic compounds, such as toluene, anisole or 2,4- dimethoxybenzene to the corresponding aldehydes. The formylating ability of systems from 4 and superacids, such as FSO3H, FSO3H/SbF5, C4F9SO3H, and mixtures of aluminum chloride with C4F9SO3H and chlorosulfonic acid, respectively, is compared. In general, low reaction temperatures (−20 to −10 °C) are necessary to obtain aldehydes with acceptable to good yields. Remarkably, at higher temperatures (~ 100 °C) compound 4 can also act as a formylating agent in the presence of suitable zeolites, as e. g. zeolite HBEA. Reaction mechanisms of the new formylation reactions are proposed.

Orthoamide, LX [1]. N,N,N’,N’-Tetraformylhydrazin – ein breit anwendbares Formylierungsmittel für aromatische Verbindungen / Orthoamide, LX [1]. N,N,N’,N’-Tetraformylhydrazine – a Formylation Agent for Aromatic Compounds of Wide Scope

Keywords The reagent system formed from N,N,N’,N’-tetraformylhydrazine (3) and aluminum chloride allows the formylation of aromatic compounds. The scope of the method is comparable with the Olah formylation and the Groß-Rieche procedure, since benzene and fluorobenzene can be formylated. Two formyl groups are transferred from 3 to the aromatic nuclei when a molar ratio 4:1:4 (aluminum chloride/3/aromatic compound) is chosen.