Heteroorganic betaines

A method for the synthesis of a new class of betaines,viz., R₃ ¹P⁺CR²R³SiR⁴R⁵S⁻, was developed. The experimental evidence for the intermediate formation of betaines R₃ ¹P⁺−CR²R³−CR⁴R⁵−S⁻ in the Wittig reaction for a series of thiocarbonyl compounds was obtained. A comparative analysis of the NMR spectra of betaines containing the⁺P−C−Si−S⁻ and⁺P−C−C−S⁻ fragments was performed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 922–930, May, 2000.     

Heteroorganic betaines

The structures of three silicon-containing organophosphorus betaines containing the⁺P−C−Si−S⁻ fragment were established by X-ray diffraction study. Due to the attractive electrostatic interaction between the anionic and cationic centers, the main chain adopts agauche conformation, whereas this chain in theS-ethyl derivative of the phosphonic salt [Ph₃P⁺−CMe₂−SiMe₂SEt]Br⁻ adopts atrans conformation. The changes in the geometric parameters of betaines depending on the substituents at the phosphorus, carbon, and silicon atoms were analyzed. The P−S bond can in principle be formed, resulting in the closure of the four-membered ring provided that additional steric hindrances at the silicon atom occur.     

Heteroorganic betaines

The [Ph₃P⁺−CMe₂−SiMe₂−SEt]Br⁻ salt was prepared by the reaction of betaine Ph₃P⁺−CMe₂SiMeR−S⁻ (1a: R=Me) with EtBr. Acetylation of betaine1a or Et₃P⁺−CHMeSiMe₂−S⁻ (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione      

Heteroorganic betaines

Photolysis and thermal decomposition of betaines R₃P−CR¹R²−SiR³R⁴−S⁻ (1) follows two main pathways: (a) a Corey—Chaykovsky type reaction with elimination of Ph₃P and generation of silathiirane (2) and (b) a retro-Wittig type reaction accompanied by elimination of R₃P=CR¹R² and generation of silanethione R³R⁴Si=S (3). Highly reactive compounds2 and3 undergo subsequent transformations to give derivatives of tetrahydro-1,4-dithia-2,5-disilin, 1,3-dithia-2,4-disilolane, and phosphonium salts ofsymm-tetraorganodisilthiane dithiolates [Ph₃P⁺CHR¹R²]₂[(R³R⁴SiS⁻)₂S]. The structures of the compounds obtained were established by X-ray diffraction analysis and multinuclear NMR spectroscopy. For part 3, see Ref. 1. The betaines Et₃P⁺CHMeSiMe₂S⁻ and Et₃P⁺CHMeSiPh₂S⁻ with alkyl groups at the phosphorus atom are distinguished by high thermal stability; their spectral characteristics do not change during storage of solutions of these compounds in pyridine-d₅ or metastable solutions in benzene-d₆ for 1–2 years at −20°C in sealed evacuated tubes or on heating (150°C) for 15 h. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1594–1603, September, 2000.     

Heteroorganic betaines

The structures of 6,6-dimethyl-6-silafulvene C₅H₄SiMe₂ (3), its donor-acceptor complex with ammonia. C₅H₄SiMe₂·NH₃, dimethylfulvene, a number of cyclopentadienylides, methylenetrimethylphosphorane (6), and silicon-containing organophosphorus betaine⁻C₅H₄SiMe₂CH₂PMe₃ ⁺ (13), the product of nucleophilic addition of6 to3, were calculated using the density functional approach. For compound13, the potential energy minimum corresponds to the conformation withgauche-arrangement of the cyclopentadienyl anionie and trimethylphosphonium cationic centers and a C−Si−C−P dihedral angle of 30.5°, which is due to the Coulomb attraction between these centers. According to calculations, betaine13 is rather stable toward decomposition into3 and6 (ΔH ^o=42 kcal mol⁻¹, ΔG ^Δ=30 kcal mol⁻¹). The main channel of thermal decomposition of compound13 involves an intramolecular nucleophilic substitution, which proceeds with elimination of trimethylphosphine and results in 1,1-dimethyl-1-silaspiro[2,4]hepta-4,6-diene, which then undergoes a ready and irreversible isomerization into 6,6-dimethyl-6-silabicyclo[3.2.0]hepta-1,3-diene owing to the [1.5]-sigmatropic shift of the C−Si bond. For Part 4, see Ref. 1. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1850–1857, November, 2000.     

Novel organosilicon betaines

The structure of organosilicon betaines R₃P⁺CMe₂SiMe₂S^– (R = Ph and Me₂N) was determined by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–340, February, 1994.     

Pseudo-cross-conjugated mesomeric betaines. 1. Synthesis of pseudo-cross-conjugated mesomeric betaines from quinoxaline derivatives

A new method for the synthesis of pseudo-cross-conjugated mesomeric betainic heterocyclic compounds with an angular nitrogen atom has been developed consisting in the reaction of 1,4-dielectrophile — -carbethoxy-2-(3-chloro)quinoxalylacetonitrile with azoles. Experimental regularities have been studied and a reaction mechanism has been proposed including the stage of formation of an ylide from a quaternary azolium salt. A pseudo-crossconjugated mesomeric betainic heterocyclic compound containing a thiazole ring compound has been synthesized for the first time.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1533, November, 1992.     

Pseudo-cross-conjugated mesomeric betaines 2. X-Ray crystallographic investigation of betaines based on quinoxaline derivatives

An x-ray crystallographic investigation of 3-methyl-5-cyanoimidazolio[1,21,6]pyrido[2,3 -b]quinoxalin-4-olate, which is a representative of a previously unknown type of polynuclear heterocyclic pseudo-crossconjugated mesomeric betaine, was undertaken.For Communication I, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1534–1538, November, 1992.     

Photochemistry of N-acylimino-isoquinolinium and -quinolinium betaines

The photochemical behavior of N-acyliminoisoquinolinium and -quinolinium betaines has been investigated. In contrast to pyridinium betaines, the principal course of reaction is the 1,2-migration of N-acylamino groups. Substituent effects as well as solvent effects are observed. The results are rationalized in terms of diaziridine intermediates.     

Determination of betaines as ultraviolet-absorbing esters

A method is described for the estimation of fully N-methylated amino acids (betaines) in plant extracts. After partial purification of aqueous extracts with ion-exchange resins, a crown ether and potassium phosphate buffer are used to facilitate the esterification of betaines with α, p-dibromoacetophenone, p-nitrobenzyl bromide or α-bromo-p-tolunitrile. The esters are isolated with dilute sulphuric acid and chloroform; 10–200 nmol can be determined spectrophotometrically, and smaller amounts by high-performance liquid chromatography.     

Amphiphilic perfluoroalkylated sulfones and sulfonate betaines

Two types of perfluoro alkyl-containing amphiphilic sulfones 7-9 and 13-15, respectively, and sulfonate betaines 23-32 were prepared using 2-[(perfluoroalkyl)methyl]oxiranes (1-3, R_F = C₄F₉, C₆F₁₃, C₈F₁₇) or 3-(perfluoroalkyl)propyl iodides (16 and 17, R_F = C₆F₁₃, C₈F₁₇) as the starting compounds. The overall yields of two-step syntheses were above 90%. The compounds 7-9 were prepared by the reaction of oxiranes 1-3 with 2-sulfanylethan-l-ol and subsequent oxidation of intermediate sulfides. Similarly, the amphiphiles 13-15 were obtained by analogous reaction of oxiranes 1-3 with thiomorpholine and subsequent oxidation of the sulfur atom in the morpholine ring. In the syntheses of betaines 23-32, the starting compounds 1-3 or 16 and 17 were first reacted with dimethylamine followed by the ring-opening reaction of the intermediate fluoroalkyl(dimethyl)amines with propane-1,3- or butane-1,4-sultones.     

Synthesis of highly symmetric mesomeric triazaphenalene betaines

The synthesis of seven mesomeric triazaphenalene betaines 4a‐g by condensation reaction of hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine 1 with diethyl malonates 2a‐g or with bis(2,4,6‐trichlorophenyl)malonates 3c,f has been achieved. The guanidine 1 forms in benzene solution a salt with trimethyl methanetricarboxylate 5 which upon heating produces 4a.     

Isocyanide-based four-component synthesis of 1,3-indandionylamidinium betaines

An efficient approach for the synthesis of novel 1,3-indandionylamidinium betaines via four-component reaction of 1,3-indandione, aldehydes, amines, and isocyanides, without assistance of any catalyst and under mild reaction conditions has been reported. The structures of these compounds were confirmed by IR, mass spectroscopic, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies.     

The mass spectra of N-acyliminopyridinium and isoquinolinium betaines

The mass spectral fragmentation behaviour of N-acyliminopyridinium and isoquinolinium betaines has been investigated. Major fragmentations of the pyridinium betaines can be rationalized in terms of charge localization on the pyridinium nitrogen. The most prominent process is α-cleavage followed by loss of NCO to furnish a pyridine ion. The electron-impact induced fragmentation of N-benzoyliminopyridinium betaine (I) was compared with that of thermolysis. The completely analogous behaviour has been observed in the corresponding isoquinolinium betaines.     

Trigonelline and other betaines in species of Laminariales

A collection of Laminariales species was made with examples in each of the presently recognized families of the order. Extracts of each species were examined for betaines, using primarily 'H NMR spectroscopy for their identification. Glycinebetaine was detected in all species tested and would appear to be a consistent feature of the Laminariales. Gamma-Aminobutyric acid betaine was found in all species of Laminaria examined and in three of the five Saccharina species (family Laminariaceae), but was not detected in species of either other genera of the family or in those of other Laminariales families. Trigonelline was found in some Laminaria and Saccharina species, as well as in the north Pacific species Postelsia palmaeformis (Laminariaceae), Pseudochorda nagaii (Pseudochordaceae) and Akkesiphycus lubricus (Akkesiphycaceae).     

Novel betaines from a micronesian sponge Dysidea herbacea

Three new betaines, dysibetaine PP (1), dysibetaine CPa (2), and dysibetaine CPb (3), were isolated from an aqueous extract of the marine sponge Dysidea herbacea collected in Yap state, Micronesia. The structure of 1 was determined by spectral methods as well as chemical degradation to be a novel dipeptide betaine, and those for 2 and 3 were determined to be unprecedented cyclopropane betaines. Compounds 2 and 3 showed weak affinity toward the N-methyl-D-aspartic acid-type and the kainic acid-type glutamate receptors, respectively, in a radioligand binding assay.     

Synthesis and structure of novel 1,2-dihydro-phthalazine containing betaines

1,2-Dihydro-2-(4,5-dihydroimidazol-2yl)phthalazin-1-ol 1 reacts exothermically with dialkyl acetylenedicarboxylates to give 3-[2-(4,5-dihydro-1H-imidazol-3-iurn-2-yl)-1,2-dihydro-1-phthalazin]-1,4-dialkoxy-1,4-dioxo-2-buten-2-olates 7 and 8 . Enolic ester compounds underwent further transesterification reactions with formation of the betaines 9 and 10 . The unequivocal structural assignement of these compounds was achieved by spectroscopic ¹H and ¹³C nmr methods as well as X-ray analysis of 7 .