Tetramethylguanidine Research Articles

ChemInform Abstract: Tetramethylguanidine (TMG)‐Catalyzed Addition of Dialkyl Phosphites to α,β‐Unsaturated Carbonyl Compounds, Alkenenitriles, Aldehydes, Ketones and Imines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tetramethylguanidine (TMG)-catalyzed addition of dialkyl phosphites to α,β-unsaturated carbonyl compounds, alkenenitriles, aldehydes, ketones and imines

Tetramethylguanidine-catalyzed addition of dialkyl phosphites to α,β-unsaturated carbonyl compounds, alkenenitriles, aldehydes and ketones constitutes a practical route to a variety of phosphonate synthons. The very mild conditions employed, together with the short reaction times, make the procedure highly versatile and tolerant to a range of functionalities. The proposed methodology is also convenient for the preparation of α-aminophosphonates.

ChemInform Abstract: Facile Synthesis of 2‐Nitroalkanols by Tetramethylguanidine (TMG)‐ Catalyzed Addition of Primary Nitroalkanes to Aldehydes and Alicyclic Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Facile synthesis of 2-nitroalkanols by tetramethylguanidine (TMG)-catalyzed addition of primary nitroalkanes to aldehydes and alicyclic ketones

Tetramethylguanidine-catalyzed addition of primary nitroalkanes to aldehydes and alicyclic ketones constitutes a practical means to perform the nitro-aldol reaction (Henry reaction). The very mild conditions employed, together with the short reaction times, make the procedure tolerant of a range of functionalities and highly versatile for the synthesis of a variety of 2-nitroalkanols.

SYNTHESIS AND STRUCTURE OF TETRAORGANOGUANIDINYL-SUBSTITUTED PHOSPHORUS-HALOGEN COMPOUNDS AND OF TRIS-N-(N′,N′,N″,N″-TETRAMETHYL) GUANIDINYL-PHOSPHONIUM SALTS

The N-(N′,N′,N′,N′-tetraorgano)guanidine-substituted dichlorophosphines 3a - 3c were prepared by the reaction of phosphorus trichloride with the corresponding guanidine or N-lithiated guanidine. The high-field shift of the α(31P) values of 3a - 3c reflects the strong electron-donating effect of the guanidinyl substituents. Attempts to achieve further substitution of chlorine in PCl3 by N′,N′,N′,N′-tehamethylguanidine (HTMG) 1a (employed as such or as its N-trimethylsilyl derivative, TMSTMG, 2) led to the formation of tris-N-(N′,N′,N′,N′-tetramethyl)guanidinylphosphonium salts such as 4. A salt containing the same cation was obtained from the reaction of bis-N-(N′,N′,N′,N′-tetramethyl)guanidinyltrichlorophosphorane 5 with magnesium. Difluoro-N-(N′,N′,N′,N′-tetramethyl)guanidinylphosphine 6 was obtained from difluorochlorophosphine and HTMG 1a. Hydrolysis of 6 led, depending upon the conditions of the reaction, either to N′,N′,N′,N′-tetramethylguanidinium phosphonofluoridate 7 or tris-N-(N′N,N′,N′-tetramethyl)guanidinylphosphonium pentafluorophosphate 8. A single crystal X-ray structure determination of 8 revealed a disordered anion and a cation with short P-N bonds, attributed to pπ-dπ: interaction. Dimethylamino-bis-N-(N′,N′,N′,N′-tetramethyl)guanidinyl-phosphine 9 and the chloro-diorganoamino-N-(N′,N′,N′,N′-tetramethyl)guanidinyl-phosphines 10 and 11 were obtained from the corresponding dichlorodiorganoaminophosphines and HTMG 1a or N-trimethylsilyl-(N′,N′,N′,N′-tetramethyl)guanidine 2.

Homoconjugated hydrogen bonds with amidine and guanidine bases Osmometric, potentiometric and FTIR studies

Five very strong N bases, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), pK a =23.4; 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),pK a =23.9; tetramethylguanidine (TMG), pK a =23.3; 2-phenyl-tetramethylguanidine (PhTMG), pK a =20.6; and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), pK a =24.97; have been studied by osmometric measurements which showed that they are monomeric in acetonitrile solutions. The constants of the formation of homoconjugated complexes were determined by potentiometric measurements. In the IR spectra of the semi-protonated complexes of DBN, DBU and TMG, the homoconjugated N + –H···NN ···H– + N hydrogen bonds cause broad band complexes in the region 3200–2500 cm -1 instead of the expected continua. This spectral peculiarity is discussed.

Kinetic and equilibrium studies of the proton and deuteron transfer reaction between bis(2,4-dinitrophenyl)methane and strong nitrogen bases in acetonitrile

Abstract Deprotonation of bis(2,4-dinitrophenyl)methane (C-acid) by tetramethylguanidine (TMG), 1,2-bis(dimethyl-aminomethyl) benzene (DMAMB) and 1,8-bis(dimethylamino)naphthalene (DMAN) in acetonitrile was studied by visible, 1 HNMR and FT-IR spectroscopy. The mixture of TMG with C-acid forms a protonated base and a product, which was different when compared with the mixtures of DMAMB or DMAN with C-acid. The spectral feature was explained as a strong electrostatic interaction between the product and the protonated TMG. Kinetic and equilibrium measurements of the reactions of C-acid with TMG, DMAMB and DMAN were completed and the kinetic isotope effects k H / k D are reported.

Methylene blue sensitized dichromated gelatin holograms: a new electron donor for their improved photosensitivity

Tetramethylguanidine (TMG) used as the electron donor in conjunction with methylene blue sensitized dichromated gelatin (MBDCG) can produce bright reflection holograms recorded at 633 nm at an exposure level of 50 mJ/cm(2). Thus DCG hologram recording and some independence from suppliers of proprietary holographic recording materials is now open to all those with low power He-Ne lasers. The high alkalinity of the system allows the unexposed coated material to have an effective lifetime at room temperature of weeks rather than days. Its low dichromate content has an environmental advantage over the usual DCG formulations. Replacement of methylene blue by eosin can produce similar photosensitivity to 514 nm. The superiority of TMG over previously reported electron donors used with MBDCG is discussed.

An improved procedure for the synthesis of DL‐[2‐13C]‐glutamic acid

AbstractA convenient two‐step chemical synthesis of DL‐[2‐13C]‐glutamic acid from methyl acrylate and diethyl acetamidomalonate is described. Synthesis of the Michael adduct (III) was effected in quantitative yield by employing strong amino bases as catalysts. The reactivities of three such catalysts, tetramethyl guanidine (TMG), 1,8‐diazobicyclo [5,4,0]‐undec‐7‐ene (1,5‐5) (DBU) and 1,5‐diazobicyclo [4,3,0] non‐5‐ene (DBN) were compared by 13C NMR and all are shown to catalyse the reaction quantitatively, however at markedly different rates.

Kinetics and mechanisms of the reaction of 2,4,6-trinitrocumene and 2,4,6-trinitroethylbenzene with 1,1,3,3-tetramethylguanidine in N,N-dimethylformamide solvent

The reaction of tetramethylguanidine (TMG) with trinitrocumene (TNC) and trinitroethylbenzene (TNEB) in dimethylformamide solvent has been studied with respect to products and kinetics. For TNC only σ-complex formation with the benzene ring was observed, for which the equilibrium constant, rate constants, and activation parameters were measured. For TNEB, both σ-complex formation and proton transfer from the σ-carbon atom of the ethyl group were observed. The equilibrium constants, rate constants, and activation parameters were separately determined for each reaction and a primary deuterium isotope effect, kH/kD = 13.6 (at 20 °C), was found for the proton transfer. The reaction parameters are compared to those for proton transfer from TNT to tetramethylguanidine in DMF solvent.

Factors influencing kinetic isotope effects in some proton-transfer reactions in aprotic solvents

Kinetic studies have been carried out on the proton-transfer reactions of (i) 4-nitrobenzyl cyanide (4-NBC) with tetramethylguanidine (TMG) and (ii) 4-nitrophenylphenylcyanomethane (4-NPPCM) with 1,8-bis(dimethylamino)naphthalene (DMAN) in acetonitrile.The reaction (i) has a moderate enthalpy of activation (ΔH‡= 25 kJ mol–1) and a negative entropy of activation (ΔS‡=–98 J mol–1 K–1). The deuterium kinetic isotope effect is large.The reaction (ii) of the more hindered molecule 4-NPPCM and DMAN has similar activation parameters (ΔH‡= 26 kJ mol–1, ΔS‡=-140 J mol–1 K–1), but the kinetic isotope effect is considerably larger; also ΔHD‡-ΔHH‡ is large (13 kJ mol–1) and AH/AD is small, indicating a considerable tunnelling effect. Evidence that the large isotope effects are not artefacts of hydrogen exchange is presented. The tunnelling factor is estimated.

Synthese simplifiee de sondes mixtes avec des triazolo-nucleosides

The incorporation of triazolo-nucleosides during the synthesis of a specific sequence yields, after treatment with a mixture of pyridine aldoximate—tetramethyl guanidine— concentrated ammonia, mixed probes oligonucleotides with practically equimolecular amounts of T/ MeC and G/ NH2A at the degenerate sites.

Structural and solvent influences on tunnelling in reactions of 4-nitrophenylnitromethane with nitrogen bases in aprotic solvents

Exceptionally large kinetic isotope effects are observed in the proton-transfer reaction of the carbon acid 4-nitrophenylnitromethane with the strong nitrogen base tetramethylguanidine (TMG) in solvents of low polarity such as toluene; values of kH/kD up to ∼50 and of AD/AH up to ∼100 have been reported. The volume of activation has been determined in several of these solvents and shows only small variations. In solvents of higher polarity, such as THF, dichloromethane or acetonitrile, the isotope effects are smaller. With tertiary amines in place of TMG as base, the isotope effects show a similar solvent-dependence but are all smaller. These effects are interpreted in terms of tunnelling. The factors influencing the tunnelling correction are discussed : (i) the dimensions of the barrier to proton-transfer (ii) possible changes of configuration in the reactant molecules, and (iii) solvent motions coupled to the proton-transfer. The data on other reactions exhibiting tunnelling are considered in the light of this discussion.

Oxidation of Thiols by Molecular Oxygen in Tetramethylguanidine

THE formation of stable alkylammonium thiolate salts from the reaction of benzenethiol with p-, sec-, and tert-aliphatic amines was first observed by Gordy and Stanford1 and further substantiated by Grillot and Brooks2. Subsequent work has demonstrated that: (a) the formation of alkylammonium thiolates from the reaction or aromatic and arakyl thiols with aliphatic amines is a general reaction; (b) that aliphatic amines catalyse the oxidation of thiols by molecular oxygen in hydrocarbon solvents3. The latter suggests that the active species in these oxidations is the thiol anion (RS ⊝). Recent investigations in these laboratories have demonstrated that dipolar solvents markedly accelerate the base-catalysed oxidation of thiols4. This finding coupled with the foregoing results suggested that tetramethylguanidine (TMG) would be capable of functioning simultaneously as both a solvent and a base for thiol oxidations. This was found to be true.