Steric effects on forming different by-products in the formylation reaction of 2,4-dialkylphenol (dialkyl = t-Bu/t-Bu, t-Bu/Me and Me/Me) proved by their structural and spectral characterizations

In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-products, namely 2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3). These three compounds are fully characterized and single-crystal structures of 1 and 3 are further elucidated.     

Synthesis and X-ray single crystal structure of first aromatic ortho-di-tert-butyl azolo[1,2,4]triazine

Oxidation of 3,4-di-tert-butyl-8-methyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine with NBS/K₂CO₃ furnished 3,4-di-tert-butyl-8-methylpyrazolo[5,1-c][1,2,4]triazine, a mildly strained heteroaromatic compound. X-Ray single crystal diffraction analysis indicated that the conjugated 1,2,4-triazine ring adopts a twist-boat configuration, while the two t-Bu substituents are located on the opposite sides of the azole plane. The related 3-tert-butyl-4-(o-C-carboranyl)-8-methyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine was also synthesized, however, its oxidative aromatization was unsuccessful.     

Photolysis of 2,6 di-tert-butyl-4-tert-butylperoxy-4-methyl-2,5-cyclohexadienone

The photolysis of a heptane solution of 2,6-di-tert-butyl-4-tert-butylperoxy-4-methyl- 2,5-cyclohexadienone (1) with light of 360–480 nm in the presence of 2,6-di-tert-butyl-4-methylphenol or 2,4,6-tri-tert-butylphenol gives rise to their corresponding phenoxyls in a reaction with the tert-butoxyl arising in the photolysis. Direct evidence of the formation of t-BuO^. by the photolysis of 1 was provided by the ESR characterization of spin-adducts of this radical with nitrosobenzene and nitrosodurene. Evidence of the photolysis of the peroxide bond in 1 is important for the mechanism of reaction of phenolic chain-breaking antioxidants.     

Déplacements Chimiques induits en RMN par un Réactif Lanthanidique: II—Analyse Conformationnelle de Sulfinamates Cycliques: Oxo-2 Oxathiazannes-1,2,3 et Oxo-2 Benzo-5,6 Dihydro-3,4 Oxathiazines-1,2,3

Re-examination of recent results in the literature about 2-r-substituted 5-c-tert-butyl-1,3,2-dioxaphosphorinanes and 3,3-dimethyl-1-oxothiethan made us select, under the indicated conditions, the static model because it is easier to use than the dynamic one. Its application to 17 cyclic sulphinamates belonging to two series—the 2-oxo-1,2,3-oxathiazans (I) and the 5,6-benzo-3,4-dihydro-2-oxo-1,2,3-oxathiazins (II)—confirms, in the presence of Eu(fod)₃, the structures established without the shift reagent, from chemical shifts and coupling constants only, and shows their conformational diversity. For the series (I) the following conformations are found: (i) standard chairs with an axial S?O group (CA) when the molecule is not substituted in the 4 and 6 positions or when the substituents are equatorial (with the exception of 3-tert-butyl-4-t-methyl-2-r-oxo-1,2,3-oxathiazan); the substituents R?Me, iPr or tBu on the nitrogen atom are preferentially axial; (ii) strained chairs with axial Me-4 and S?0 groups (CA); in this conformation R?Ph may be partially conjugated and R?Me or tBu may prefer the more favourable axial orientation; (iii) twist conformations with a 1,4-axis and an axial S?O group (COA) for the two 4-c,6-c- and 4-t,6-c-di-tert-butyl-2-r-oxo-3-phenyl-1,2,3-oxathiazans; (iv) the twist conformation with a 3,6-axis and an axial S?O group (CNA) for trans-3-tert-butyl-4-methyl-2-oxo-1,2,3-oxathiazan because of the 4-methyl—3-tert-butyl 1,2-interaction. For the series (II) half-chair forms with an axial S?O group are proposed.     

Regio-selective synthesis of novel 1-tert-butyl-4-nitro-1H-pyrrole-3-carboxylic acid building block

A convenient, regio-selective synthesis of novel 1-tert-butyl-4-nitro-1H-pyrrole-3-carboxylic acid was developed, utilizing the bulky tert-butyl moiety of 1-tert-butyl-1H-pyrrole to direct selective, un-symmetrical substitutions to the desired 3 and 4 positions.     

3-Hydrazino-1,2,4-triazin-5(2H)-ones in Reactions with Compounds Containing Carbonyl and Active Methylene Groups

Boiling of ethyl cyanoacetate with 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one in alkalinemedium yielded 6-tert-butyl-3-(5-hydroxy-3-oxo-2'3-dihydro-1H-pyrazol-1-yl)-1'2'4-triazin-5(2H)-one.Acylation of 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one with benzoyl chloride furnished 3-benzoyl-hydrazido-1'2'4-triazine that cyclized when treated with POCl₃ providing a derivative of[1'2'4]triazolo[4'3-b][1'2'4]triazine. Boiling of 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one in glacialacetic acid gave rise to diacetylated derivative whereas the boiling with acetic anhydride in an inert solventafforded monoacetylated product.     

Synthesis oftert-butyl substituted polymethine 1-benzothiopyrylium dyestuffs

A series of polymethine thiopyrylium dyestuffs of symmetrical and unsymmetrical structure, containing one to fourtert-butyl groups, has been synthesized from 6-tert-butyl-2-(p-tert-butylphenyl)-4-methyl-, 4,6-di(tert-butyl)-2-methyl-, and 6-tert-butyl-2,4-dimethyl-1-benzothiopyrylium perchlorates.     

Synthesis of 8-alkylthio- and 8-selanyl-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines

Abstract

Interaction of 8-lithio-3-tert-butyl-4-oxopyrazolo[5,1-c][1,2,4]triazin-1-ide with elemental sulfur or selenium in THF with further in situ alkylation at –97?°C followed by warming to room temperature furnished a series of 3-tert-butyl-8-X-pyrazolo[5,1-c][1,2,4]triazin-4(6H)-ones (X?=?n-BuS, n-BuSe, MeSe, PhCH₂S) in good yields. 8,8'-Diselanediylbis(3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4(1H)-one) was also isolated as a by-product in these reactions. One-pot interaction of the n-BuSe substituted derivative with diborane/boron trifluoride led to reduction of the 1,2,4-triazine core and partial elimination of the alkylselanyl moiety. The structures of the synthesized products were established on the basis of IR, ¹H, 13C, 2D HMBC ¹H–⁷⁷Se NMR and high resolution mass spectra, as well as X-ray single crystal diffraction analyses. Two of the prepared compounds were also tested for antimicrobial and antifungal activities.     

Synthese und Struktur von Tetrachloro[4-tert-butyl-2(diphenylphosphanyl-κP-methyl)phenolato-κO]tantal(V), ein neuartiger TaV-Komplex mit einem chelatisierenden Aryloxyphosphanliganden

Synthesis and Structure of Tetrachloro[4- tert -butyl-2(diphenylphosphanyl-κP-methyl)phenolato-κO]tantalum(V), a Novel Ta^V Complex with a Chelating Aryloxy Phosphane Ligand 4-tert-Butyl-2-(diphenylphosphanylmethyl)anisol ( 1 ) is prepared from 2-chlormethyl-4-tert-butylanisol and potassium diphenylphosphide in very good yields as a novel oxygen-phosphorus compound with potentially hemilabile ligand properties. Compound 1 reacts with tantalum pentachloride under cleavage of methylchloride revealing the complex tetrachloro[4-tert-butyl-2-(diphenylphosphanyl-κP-methyl)phenolato-κO]tantalum(V) ( 2 ) with a distorted octahedrally coordinated tantalum atom and a chelating aryloxy phosphane ligand. Complex 2 crystallizes in the tetragonal, chiral space group P4₁2₁2 with a = 11.719(5), c = 37.95(5) Å, V = 5171(7) ų, Z = 8. ³¹P NMR spectroscopic studies of 2 establish the coordination of the phosphane unit to the Ta^V center in solution.     

Conformational and Configurational Determination in 1,1,4,4-Tetrafluoro-2-Propylidene-3-Methyl-6-Tert-Butyl-1,4-Disila-5-Cyclohexene

A complete assignment of the ¹H, ¹³C and ¹⁹F NMR spectra of 1,1,4,4-tetrafluoro-2-propylidene-3-methyl-6-tert-butyl-1,4-disila-5-cyclohexene 3, the product of the cycloaddition reaction between tetrafluorodisilacyclobutene 1 and cis, trans-2,4-hexadiene mediated by (n⁵-C₅H₅)Mn(CO)₃, has been made by means of various 2D NMR chemical shift correlation methods and selective heteronuclear decoupling techniques. An analysis of the three bond ¹³C-¹H coupling constants and two bond ¹³C-¹⁹F coupling constants and the molecular modeling results enabled the determination of the conformation and configuration of compound 3. The conformation of 3 provides insight into mechanistic details of the Mn-mediated cycloaddition.     

Interactions intramoléculaires. XXVI—Constantes de couplage et hétérogénéités conformationnelles dans une série de R-3 et R-5 cyano-4 cyclohexènes deutériés (R=méthyl ou t-butyl)

For trans-3-R- and 5-R-1-acetoxy-4-cyanocyclohexene-6,6-d₂ the molar fractions of diequatorial conformers are 0.83 (3-methyl), 0.68 (5-methyl), 0.57 (3-tert-butyl) and 0.55–0.69 (5-tert-butyl). For the last two compounds the values of the coupling constants are in agreement with the hypothesis of an ee?aa equilibrium. For the cis isomers, the molar fractions of equatorial alkyl conformers are 0.76 (3-methyl and 5-methyl) and 1.0 (3-tert-butyl and 5-tert-butyl). The cis-1-acetoxy-3-tert-butyl-4-methoxycarbonyl-cyclohexene presents a conformational heterogeneity. The conformational free energy of the methyl group in position 4 has been evaluated as ?0.6 kcal mol^?1 (2.5 kJ mol^?1).     

Synthesis of Halomethyl Derivatives of 3- and 4-(Dialkoxyphosphorylmethyl)-5-tert-butylfuran-2-carboxylic Acid and Their Reactions with Nucleophilic Agents

5-tert-Butyl-4-chloromethyl-, 5-tert-butyl-4-(diethoxyphosphorylmethyl)-3-methylfuran-2-carboxylates are effectively brominated with N-bromosuccinimide by the 3-methyl group. The bis(halomethyl)derivative is phosphorylated under conditions of the Arbuzov reaction to give the corresponding chloromethylphosphonate. The obtained organophosphorus derivatives of bromomethyl- and chloromethylfuran-2-carboxylic acid react with secondary amines and sodium butanethiolate to form the corresponding substitution products. Alkyl 5-tert-butyl-4-chloromethyl-3-(diethoxyphosphorylmethyl)-furan-2-carboxylate reacts with sodium acetate in acetic acid to give a 4-acetoxymethyl derivative. It is the first example of a facile reaction with O-nucleophiles of halomethyl derivatives of phosphonomethylated furans.     

Heterocyclization of 6-tert-Butyl-3-hydrazino-2,5-dihydro-1,2,4-triazin-5-one with Benzoyl Chloride and Formic Acid

Reaction of 6-tert-butyl-3-hydrazino-2,5-dihydro-1,2,4-triazin-5-one with excess benzoyl chloride or formic acid afforded 6-tert-butyl-[1,2,4]triazolo[4,3-b][1,2,4]triazin-7(8H)-ones.     

Determination of the configuration in six-membered saturated heterocycles (N,P, S,Se) and their oxidation products using experimental and calculated NMR chemical shifts

The six-membered saturated heterocycles—4-tert-butyl-1-methylpiperidine, 4-tert-butyl-1-methylphosphine, 4-tert-butyl-tetrahydro-2H-thiopyran, and 4-tert-butyl-tetrahydro-2H-selenopyran—were prepared as suitable model compounds with well-defined geometry for an NMR study of their oxidation products. The corresponding epimeric N-oxides, phosphinoxides, sulfoxides, and selenoxides were obtained by standard chemical preparation and also by in situ oxidation with meta-chloroperbenzoic acid directly in the NMR tube. The experimental ¹H and ¹³C chemical shifts were compared with corresponding calculated data obtained by GIAO approach with DFT, MP2, and HF methods and various basis sets. The correlation of experimental versus calculated data showed the possibility to determine the stereochemistry of the epimeric oxidation products using fast DFT B3LYP/6-31G* method for both geometry optimization and NMR chemical shifts calculation.     

Beiträge zur Chemie des Phosphors. 87. 1,2-Di-tert-butyl-3-iso-propyl-cyclotriphosphan,ein stabiles gemischt-substituiertes Cyclotriphosphan

Contributions to the Chemistry of Phosphorus. 87. 1,2-Di-tert-butyl-3-iso-propyl-cylclotriphosphane, a Stable Mixed-substituted Cyclotriphosphane The first kinetically stable mixed-substituted cyclotriphosphane, 1,2-di-tert-butyl-3-iso-propyl-cyclotriphosphane, (PBu^t)₂(PPrⁱ) ( 1 ), was synthesized by [2+1]-cyclocondensation of K(Bu^t)P–P(Bu^t)K with PrⁱPCl₂ in n-pentane. Mainly (PBu^t)₄ as well as mixed-substituted cyclotetra- and cyclopentaphosphanes are formed as by-products. 1 could be isolated in a pure state by high vacuum distillation and was thoroughly characterized. It forms two diastereomers, the more stable of which with a cis-standing tert-butyl and iso-propyl group can be stored without decomposition under inert conditions at room temperature for several days. Through thermolysis of 1 beside other alkylcyclophosphanes the mixed-substituted cyclotetraphosphanes (PBu^t)₂(PPrⁱ)₂ ( 2 ) and (PBu^t)₃(PPrⁱ) ( 3 ) are formed and their ³¹P NMR parameters are reported.     

1H NMR Study of Quaternization of 2,4-Di-tert-butyl-6-dimethylaminomethylphenol

The possibility was revealed for exhaustive protonation of 2,4-di-tert-butyl-6-dimethylaminomethylphenol with participation of lone electron pairs on both nitrogen and oxygen atoms. The reaction of the title compound with alkyl halides includes concurrent and consecutive processes leading to formation of the corresponding hydrohalides and quaternization products. The latter undergo spontaneous oxidation with atmospheric oxygen to give quaternary 6,8-di-tert-butyl-3-methyl-2H-3,4-dihydro-1,3-benzoxazine derivatives which were detected by ¹H NMR spectroscopy.     

Polarographic and voltammetric behaviour of 2-hydroxy-3-tert-butyl-5-methylazobenzene

The polarographic and voltammetric behaviour of 2-hydroxy-3-tert-butyl-5-methylazobenzene has been studied in aqueous-ethanol mixtures of different pH using DCP and DPP polarographic and CV and SWV voltammetric methods. The reduction of the azo linkage takes place via two electrons at pH > 7, but four electrons at pH < 7 in aqueous-ethanol mixtures. It has been determined that there is a linear relationship between the current and concentration and the lowest detection limit has been found as 1 × 10^–7 M (for SWV).     

Synthetic and structural study of 4-phosphacyclohexanones and 3-aza-7-phosphabicyclo[3.3.1]nonan-9-ones

The synthesis of bicyclic phosphorus–nitrogen (PN) compounds containing the rigid bicyclo[3.3.1]nonan-9-one framework was attempted using the Mannich condensation reaction of four different phosphorinanone classes with amines and aldehydes. Three different isomers of 4-tert-butyl-2,6-di(methoxycarbonyl)-3,5-bis(p-dimethylaminophenyl)-4-phosphacyclohexanone were obtained from the Michael addition reaction of tert-butylphosphine with 2,4-di(methoxycarbonyl)-1,5-bis(p-dimethylaminophenyl)penta-1,4-dien-3-one. The reaction of the all-equatorial isomer with methylamine and formaldehyde produced the bicyclic PN compound 7-tert-butyl-1,5-di(methoxycarbonyl)-6,8-bis(p-dimethylaminophenyl)-3-methyl-3-aza-7-phosphabicyclo[3.3.1]nonan-9-one. The identical Mannich reaction of the enol tautomer also yielded the same product, as well as the PN compound 4-tert-butyl-6-methoxycarbonyl-5-(p-dimethylaminophenyl)-2-methyl-2-aza-4-phosphacyclohexanone and the E/Z isomers of 3-(p-dimethylaminophenyl)methyl-2-propenoate. The newly synthesised 3-aza-7-phosphabicyclo[3.3.1]nonan-9-one PN compound adopts a chair–chair conformation both in solution and the solid state.     

Synthesis and Structure of 1-tert-Butyl-3-R-tetrazolium Salts

An effective method was developed for the synthesis of 1,3-disubstituted tetrazolium salts by the quaternization of 2-monosubstituted tetrazoles, including functionally substituted compounds, with tert-butanol in 72% perchloric acid. An X-ray diffraction investigation of examples of this series of salts - 1-tert-butyl-3-(1-methylvinyl)- and 1,3-di-tert-butyltetrazolium perchlorates - was carried out.     

3-Phenylpropylamines,A New Class of Systemic Fungicides

The biological activity of 3-phenylpropylamines is not exclusively determined by their structure. It could be demonstrated that the fungicidal activity of partially hydrogenated compounds of this class of substances is also substantially influenced by the conformation. An optimization of the conformational criteria—illustrated by many examples, yet constituting only a small number of those actually examined—afforded compounds with excellent properties, e.g. N-[3-(4-tert-butyl-1-cyclohexenyl)-2-methylpropyl]-cis-2, 6-dimethylmorpholine.