Photostabilizing activity of N-acylated hindered amine

The influence of the acyl groups of N-acylated hindered amine on the photostabilization of polymers was discussed. The effects of the N-acyl derivatives of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine ( 6 ) in the photostabilization of polypropylene were compared. Although the stabilizing effects of all the N-acyl derivatives were lower than that of the N-oxyl derivative ( 7 ), N-acryloyl ( 4 ) and N-benzoyl ( 5 ) derivatives showed higher effects than that of parent N? H 6 . To discuss the stabilizing mechanism of N-acylated hindered amine, the reaction of N-acylated hindered amine with model hydroperoxide (tert-butyl hydroperoxide) was carried out at an elevated temperature (132°C). N-Acylated hindered amine decomposed tert-butyl hydroperoxide more rapidly than corresponding secondary hindered amine, and changed into the parent secondary amine.     

Approaches to primary tert-alkyl amines as building blocks

Primary tert-alkyl amines include analogues of amantadine, a fragment commonly linked to pharmacophoric groups to enhance biological activity. The preparation of primary tert-alkyl amines is considered to be a difficult problem. Four synthetic procedures, some of which have been previously reported for the synthesis of amines with primary (RCH₂NH₂) or secondary (RR'CHNH₂) alkyl and/or aryl groups, were tested for the synthesis of primary tert-alkyl amines (RR′R″CNH₂) in aliphatic series including adamantane adducts. These procedures included the formation and reduction of tert-alkyl azides, the Ritter reaction in standard and modified conditions, the addition of organometallic reagents to N-tert-butyl sulfinyl ketimines and one-pot reactions between nitriles and organometallic reagents in the presence of a Lewis acid, Τi(iPrO)₄ or CeCl_3. These synthetic routes are unexplored for primary tert-alkyl amines. Studies on the synthetic routes for primary tert-alkyl amines are currently lacking. The reaction conditions and substrate limitations were studied for each procedure, with the first procedure being the most general and applicable also for compounds bearing bulky adducts.     

Synthesis of N-Sulfonylformamidines by tert-butyl Hydroperoxide–Promoted,metal-free,direct oxidative dehydrogenation of aliphatic amines

A direct and convenient metal-free method to prepare sulfonyl amidines in the presence of aqueous tert-butyl hydroperoxide (T-HYDRO) has been developed. Different tertiary and secondary amines were tested for compatibility with the oxidative conditions and could be coupled with sulfonyl azides to form the corresponding amidines in moderate to good yields.     

Amide bond synthesis via silver(I) N-heterocyclic carbene-catalyzed and tert-butyl hydroperoxide-mediated oxidative coupling of alcohols with amines under base free conditions

We present a base free method for amide bond construction via oxidative coupling of alcohols with amines catalyzed by Silver(I) N-heterocyclic carbenes (Ag(I)-NHCs) and mediated by tert-butyl hydroperoxide (TBHP) in ethanol. The results of controlled experiments suggest that the oxidative coupling proceeds through the formation of aldehyde, then subsequent attack by amine to give hemiaminal, which can then be oxidized to amide.     

Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and <Emphasis Type="Italic">tert</Emphasis>-Butyl Isocyanide in the Presence of Primary or Secondary Amines

Summary. 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrums acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N-tert-butyl-2,2-dimethylbutyramide derivatives and/or 1-tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.     

Synthesis and thermal properties of azo-peroxyesters

Abstract  

New azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained in reactions of azo acid chlorides with hydroperoxides in the presence of an inorganic base. Obtained azo-peresters possess two kinds of the labile functional groups: the azo group and also the perester group. The data from DSC experiments indicate that in the case of azo-perester derivatives of tert-amyl hydroperoxide, the perester group decomposes at a somewhat lower temperature than in the case of tert-butyl derivatives, whereas azo groups decompose at somewhat higher temperature in the case of derivatives with tert-amyl substituent.     

A direct functionalization of tertiary alkyl bromides with O-, N-, and C-nucleophiles

Silver oxide used in stoichiometric amounts promoted the direct functionalization of tert-alkyl bromides and provided the desired adducts in 39-96% isolated yield. Reaction of tert-bromides with carboxylic acids yielded esters, with alcohols and phenols yielded alkyl and aryl ethers, with amines and anilines yielded selectively mono-alkylated amines and anilines, and with a C-nucleophile yielded an all-carbon quaternary hydrocarbon. The method was applied to a sequential alkylation of a primary amine with two different alkyl bromides yielding selectively a tertiary amine with three different substituents in one-pot.     

Methyl‐Selective α‐Oxygenation of Tertiary Amines to Formamides by Employing Copper/Moderately Hindered Nitroxyl Radical (DMN‐AZADO or 1‐Me‐AZADO)

Methyl‐selective α‐oxygenation of tertiary amines is a highly attractive approach for synthesizing formamides while preserving the amine substrate skeletons. Therefore, the development of efficient catalysts that can advance regioselective α‐oxygenation at the N‐methyl positions using molecular oxygen (O₂) as the terminal oxidant is an important subject. In this study, we successfully developed a highly regioselective and efficient aerobic methyl‐selective α‐oxygenation of tertiary amines by employing a Cu/nitroxyl radical catalyst system. The use of moderately hindered nitroxyl radicals, such as 1,5‐dimethyl‐9‐azanoradamantane N‐oxyl (DMN‐AZADO) and 1‐methyl‐2‐azaadamanane N‐oxyl (1‐Me‐AZADO), was very important to promote the oxygenation effectively mainly because these N‐oxyls have longer life‐times than less hindered N‐oxyls. Various types of tertiary N‐methylamines were selectively converted to the corresponding formamides. A plausible reaction mechanism is also discussed on the basis of experimental evidence, together with DFT calculations. The high regioselectivity of this catalyst system stems from steric restriction of the amine‐N‐oxyl interactions.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature

Commercially available copper(II) tetrafluoroborate hydrate was found to be a highly efficient catalyst for chemoselective N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions and at room temperature. Various aromatic amines were protected as their N-tert-butyl carbamates in high yields and in short times. No competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation was observed. Chemoselective N-tert-butoxycarbonylation was achieved with substrates bearing OH and SH groups. Chiral α-amino acid esters afforded the corresponding N-t-Boc derivatives in excellent yields.     

Macromolecular antioxidants based on polysaccharides and 2,6-diisobornyl-4-methylphenol derivatives

New macromolecular antioxidants that were conjugates of dextran or hydroxyethylated starch with functionalized derivatives synthesized from 2,6-diisobornyl-4-methylphenol were prepared. Their antiradical activity compared with derivatives of 2,6-di-tert-butyl-4-methylphenol was studied in a model reaction with 2,2-diphenyl-1-picrylhydrazyl. The studied conjugates exhibited greater activity than sterically hindered phenols not bonded to a polymer chain. The synthesized isobornyl derivatives were more active than previously studied tert-butyl analogs.     

Synthesis and thermal properties of azo-peroxyesters

Abstract  New azo-perester derivatives of tert-butyl and tert-amyl hydroperoxides were obtained in reactions of azo acid chlorides with hydroperoxides in the presence of an inorganic base. Obtained azo-peresters possess two kinds of the labile functional groups: the azo group and also the perester group. The data from DSC experiments indicate that in the case of azo-perester derivatives of tert-amyl hydroperoxide, the perester group decomposes at a somewhat lower temperature than in the case of tert-butyl derivatives, whereas azo groups decompose at somewhat higher temperature in the case of derivatives with tert-amyl substituent. Graphical abstract        

Studies in tertiary amine oxides. III—carbon-13 NMR assignment of N-alkynyl cyclic amines

Carbon-13 NMR spectra of 24 N-alkynyl cyclic amines were analysed. The effect of substituting the acetylenic proton by n-butyl, tert-butyl and phenyl groups was determined.     

Organocatalytic conjugate addition of α-nitroacetates to β,γ-unsaturated α-keto esters and subsequent decarboxylation: synthesis of optically active δ-nitro-α-keto esters

Organocatalytic asymmetric conjugate addition of tert-butyl nitroacetates to β,γ-unsaturated α-keto esters has been developed. The subsequent in situ hydrolysis-decarboxylation of the adducts provided 5-nitro-2-oxopentanoates. A pyrrolidine-based thiourea-tertiary amine was identified as the best catalyst. A number of γ-aryl, γ-alkyl, and γ-heteroaryl β,γ-unsaturated α-keto esters and α-substituted tert-butyl nitroacetates were examined in the transformation. Generally 5-nitro-2-oxopentanoates were obtained in good yields (up to 97%) and enantioselectivities (up to 94% ee). The products were readily transformed to chiral proline derivatives by catalytic hydrogenation.     

Adamantylazoles: XIV. Acid-catalyzed alkylation of 5-aminotetrazoles with tertiary alcohols

Alkylation of 5-aminotetrazole with tert-butyl alcohol or adamantan-1-ol in sulfuric acid gave a mixture of isomeric N ¹- and N ²-alkyl derivatives, as well as 1,3-dialkyl-5-aminotetrazolium salt. Adamantylation of 1-substituted 5-aminotetrazoles led to the formation of mixtures of 1,3- and 1,4-disubstituted 5-aminotetrazolium salts which can be converted into the corresponding free bases.     

Synthesis and Structure–Activity Correlation Studies of Secondary‐ and Tertiary‐Amine‐Based Glutathione Peroxidase Mimics

In this study, a series of secondary‐ and tertiary‐amino‐substituted diaryl diselenides were synthesized and studied for their glutathione peroxidase (GPx) like antioxidant activities with H₂O₂, cumene hydroperoxide, or tBuOOH as substrates and with PhSH or glutathione (GSH) as thiol cosubstrates. This study reveals that replacement of the tert‐amino groups in benzylamine‐based diselenides by sec‐amino moieties drastically enhances the catalytic activities in both the aromatic thiol (PhSH) and GSH assay systems. Particularly, the N‐propyl‐ and N‐isopropylamino‐substituted diselenides are 8–18 times more active than the corresponding N,N‐dipropyl‐ and N,N‐diisopropylamine‐based compounds in all three peroxide systems when GSH is used as the thiol cosubstrate. Although the catalytic mechanism of sec‐amino‐substituted diselenides is similar to that of the tert‐amine‐based compounds, differences in the stability and reactivity of some of the key intermediates account for the differences in the GPx‐like activities. It is observed that the sec‐amino groups are better than the tert‐amino moieties for generating the catalytically active selenols. This is due to the absence of any significant thiol‐exchange reactions in the selenenyl sulfides derived from sec‐amine‐based diselenides. Furthermore, the seleninic acids (RSeO₂H) derived from the sec‐amine‐based compounds are more stable toward further reactions with peroxides than their tert‐amine‐based analogues.     

Synthesis of Alkyl 2-Bromomethyl-4-(diethoxyphosphorylmethyl)-5-tert-butylfuran-3-carboxylates and Their Reactions with Nucleophilic Agents

Alkyl 2-methyl-4-(diethoxyphosphorylmethyl)-5-tert-butylfuran-3-carboxylates are selectivelybrominated with N-bromosuccinimide at the methyl group in position 2 of the ring. The resulting bromo-methyl derivatives react with secondary amines to form tertiary amines, with sodium butylthiolate inmethanol to form the corresponding sulfide. The reaction with potassium thiocyanate in DMF at 80°C givesa mixture of thiocyanate and isothiocyanate. When treated with phenolate or alcoholate ions, the bromomethylfurans decompose.     

Effect of alcohols on the gamma-radiation-induced polymerization of ethylene

Gamma-radiation-induced polymerization of ethylene in alcohols such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl alcohols was carried out under a pressure of 400 kg./cm.²at 30°C. at a dose rate of 1.4 × 10⁵ rad/hr. in a batch reactor of 100 ml. capacity. The yield and molecular weight of polymer formed in the alcohols (except tert-butyl alcohol) were much lower than those of the bulk polymerization under the same conditions, whereas the addition of tert-butyl alcohol increased the yield and reduced the molecular weight. From the infrared spectra of the polymers and those of the bromination products it was concluded that only primary OH exists in the polymer formed in methyl alcohol and that both primary and secondary OH are in the polymer formed in other primary alcohols. Both secondary and tertiary OH were observed in the polymer when the secondary alcohols were used, and only tertiary OH in the case of tert-butyl alcohol. These polymers were found to contain small amounts of vinylidene unsaturation and methyl group. On the basis of these results the roles of the alcohols in the polymerization are discussed.     

A new synthetic approach to phenothiazine-2-amines

Elaboration of a Buchwald-Hartwig protocol for the introduction of amino functions to position 2 of the phenothiazine ring system has opened a new access to various N-alkyl and N-dienyl phenothiazines bearing secondary amines, tertiary amines, and amide moieties. Hydrolysis of the amido derivatives gave unsubstituted phenothiazine-2-amines. This protocol provides an easy access to phenothiazine-2-amines starting from the commercially available starting compounds.     

New method for the synthesis of β-tropolones: Structures of condensation products of o-quinones with 2-methylquinolines and the mechanism of their formation

A new method was developed for the synthesis of functionalized β-tropolones based on acid-catalyzed condensation of 2-methylquinoline derivatives with 3,5-di(tert-butyl)-1,2-benzoquinone and 4,6-di(tert-butyl)-3-nitro-1,2-benzoquinone (14). The mechanism of the multistep reaction giving rise to β-tropolones and their tautomerism were studied by quantum chemical methods (DFT B3LYP/6-31G**). The reaction of 2-methylquinoline derivatives containing the tertiary amino group at position 4 with quinone 14 is accompanied by the formation of derivatives of a new heterocyclic system, viz., 4,6-dioxo-2-azabicyclo[3.3.0]octa-2,7-diene N-oxide. The molecular and crystal structures of two 5,7-di(tert-butyl)-3-hydroxy-2-(quinolin-2-yl)tropolones and two dioxoazabicyclooctadiene N-oxides, as well as of the preparatively isolated intermediate of the first condensation step and of the by-product of the reaction were established by X-ray diffraction. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1956–1977, November, 2006.     

Functionalization of sterically hindered <Emphasis Type="Italic">o</Emphasis>-benzoquinones: amino-substituted 3,6-di(<Emphasis Type="Italic">tert</Emphasis>-butyl)-<Emphasis Type="Italic">o</Emphasis>-benzoquinones

New sterically hindered functionalized o-quinones were synthesized by the 1,4-nucleophilic addition of secondary cyclic amines to 3,6-di(tert-butyl)-o-benzoquinone. The ability of these o-quinones to form o-semiquinone complexes with transition and main-group metals was studied by ESR spectroscopy in solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1786–1793, September, 2007.