Neutral pi-associated porphyrin [2]catenanes

A series of neutral porphyrin-containing catenanes has been synthesised, consisting of a zinc porphyrin strapped by a polyethylene glycol chain containing four or six ethylenoxy-units and incorporating a central naphthoquinol unit, interlinked with a naphthalene diimide macrocycle. The napthalene diimide precursor units exhibit only weak binding with the strapped porphyrins (Ka between 8 and 0.02 M(-1)), but good yields of the catenanes were obtained by Glaser coupling of the alkynyl napthalene diimide precursors in the presence of the porphyrins. Structures and solution conformations were determined by mass spectral and detailed 1H NMR studies. For the longer strapped porphyrins, the diimide macrocycle rotates around the central naphthoquinol unit at 420-450 times per second, while rotation is virtually prevented in the tighter strapped derivatives. A second dynamic process occurring in both sets of catenanes and described as 'yawing' leads to inequivalence in the naphthalene moieties. UV-Visible spectra indicate charge transfer interactions and electronic communication between the two components of the catenane.     

A Synthesis of Exiguaquinol Dessulfate

A concise and stereoselective synthesis of exiguaquinol dessulfate is described. Sequential application of a Diels–Alder cycloaddition, a desymmetrizing aldol addition, and a reductive Heck cyclization established most of the architecture of exiguaquinol, and a carefully choreographed introduction of the polar substituents afforded the title compound; unfortunately, naphthoquinol sulfation could not be achieved to deliver exiguaquinol. Our hypothesis regarding the configurational preference of the N‐acyl hemiaminal, which was based upon an analysis of internal hydrogen‐bonding interactions with polar functional groups, was proven correct. A late‐stage intermediate did not demonstrate bactericidal activity against H. pylori cultures.     

Photostabilizing activity of tertiary hindered amines

The influence of the N-alkyl group of tertiary hindered amines on the photostabilization of polymers was studied. The photostabilizing effects of the tertiary amine derivatives of 4-benzoyloxy-2,2,6,6-tetramethylpiperidine ( 1a ) in polypropylene were compared. All tertiary amine derivatives having α-H to hindered N showed higher effectiveness than 1a . Model liquid phase photoxidations were carried out by irradiating (UV-lamp) the solutions of tertiary hindered amines containing tert-butyl hydroperoxide as a photoinitiator. The tertiary hindered amines were oxidized more easily than corresponding parent hindered amine and converted to the parent amine, which was identified as its salt, resulting from the carboxylic acid produced from the N-alkyl group by oxidation. The thermal reaction of the tertiary hindered amines with tert-butyl hydroperoxide was also studied in the liquid phase. The tertiary hindered amines decomposed tert-butyl hydroperoxide more rapidly than the parent secondary hindered amine, and generated the parent amine. It was also found that the photostabilizing effects of tertiary hindered amines for polyolefins were higher than that of the parent secondary hindered amine.     

Kinetic and Dynamic Kinetic Resolution of Racemic Tertiary Bromides by Pentanidium‐Catalyzed Phase‐Transfer Azidation

We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium‐catalyzed kinetic resolution (KR) of racemic tertiary bromides under base‐free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a S_N2X pathway.     

Transalkylation of N-methyl tertiary amines with 3, 4-dibromobutenolides

The selective transalkylation of N-methyl tertiary amines with 3,4-dibromobutenolides is described.The N-methyl group of the parent tertiary amines was replaced by alkenyl units of the butenolides;and a series of butenolide-containing tertiary enamines were obtained in moderate to good yields.Interestingly,the product 2b has shown a promising anticancer activity against HeLa cell lines(IC50=0.19 mmol/L).     

Kinetic and Dynamic Kinetic Resolution of Racemic Tertiary Bromides by Pentanidium-Catalyzed Phase-Transfer Azidation

We have developed a method to afford enantiomerically enriched tertiary azides and bromides through pentanidium-catalyzed kinetic resolution (KR) of racemic tertiary bromides under base-free conditions. We found that the absence of water is crucial to attain a high selectivity factor (s). On the other hand, new experimental observations and DFT modeling led us to propose that enantioconvergent azidation of tertiary bromides proceeded through dynamic kinetic resolution (DKR). The investigations particularly identified the crucial roles of base and water in the enantioconvergent process, thus supporting the proposal that the tertiary bromide isomerizes in the presence of base and water through a S_N2X pathway.     

Polymers of tertiary amines

Polymers of tertiary amines and their hydrochlorides of molecular weights in the range 300–2000 have been prepared, starting from trans-1,4-dichlorobutene-2, and primary amines. The polymers present interesting solubility properties. Variation of the reaction conditions leads to crosslinked insoluble polymers. Reaction of the soluble tertiary amine polymers with organic acid dichlorides leads to polymers of tertiary amine–amides, a new type of polymer.     

Cross‐Coupling of Secondary Amides with Tertiary Amides: The Use of Tertiary Amides as Surrogates of Alkyl Carbanions for Ketone Synthesis

In recent years, exciting progress has been made in the field of direct transformation of amides, nevertheless, the condensation between two amides remains rare and restricted to homo‐coupling reactions. Herein, we report the cross‐coupling of secondary amides with tertiary amides, which provides a synthesis of ketones under mild conditions, and features the use of tertiary amides as surrogates of alkyl carbanions. The method relies on the coupling of enamines, generated from tertiary amides by catalytic partial reduction of tertiary amides with Vaska's catalyst, with nitrilium ions, formed in situ from secondary amides via activation with trifluoromethanesulfonic anhydride, and on the subsequent deformylation.     

A facile method for the rapid and selective deprotection of methoxymethyl (MOM) ethers

We describe a rapid and efficient method for selective deprotection of methoxymethyl (MOM) ethers using ZnBr₂ and n-PrSH, which completely removed MOM from diverse MOM ethers of primary, secondary, and tertiary alcohols or phenol derivatives. The deprotection takes less than ten minutes with both high yield and selectivity in the presence of other protecting groups. In addition, the rapid deprotection of MOM ethers of tertiary hydroxyls in high yield with no epimerization allows MOM to be a suitable protecting group for tertiary alcohols.     

Three component ketocoumarin, amine, maleimide photoinitiator I

An N-substituted maleimide has been used in conjunction with ketocoumarins and a tertiary amine to initiate the polymerization of 1,6-hexanedioldiacrylate in both the UV (365/366 nm) and visible region (436 nm) of the electromagnetic spectrum. The rate of polymerization of three ketocoumarin/tertiary amine combinations are significantly increased by the addition of a N-substituted maleimide, presumably due to oxidation of the coumarin ketyl radical formed by interaction between the triplet state of the ketocoumarin and the tertiary amine.     

Light-Mediated Formal Radical Deoxyfluorination of Tertiary Alcohols through Selective Single-Electron Oxidation with TEDA2+.

The synthesis of tertiary alkyl fluorides through a formal radical deoxyfluorination process is described herein. This light-mediated, catalyst-free methodology is fast and broadly applicable allowing for the preparation of C−F bonds from (hetero)benzylic, propargylic, and non-activated tertiary alcohol derivatives. Preliminary mechanistic studies support that the key step of the reaction is the single-electron oxidation of cesium oxalates—which are readily available from the corresponding tertiary alcohols—with in situ generated TEDA^2+. (TEDA: N-(chloromethyl)triethylenediamine), a radical cation derived from Selectfluor®.     

Regioselective Insertion of o‐Carborynes into the α‐C?H Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines

o‐Carboryne can undergo α‐C H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes.     

Restricted rotation in amides. VII—methods of resonance assignment in tertiary amides—an evaluation

Examination and evaluation of various methods for resonance assignments in amides reveals that only three of these are reliable: (a) the nuclear Overhauser effect, which leads to unequivocal results in tertiary amides; (b) the aromatic solvent induced shift, which is rapid and accurate for tertiary amides without polar substituents; (c) the lanthanide-induced shift, which although easy, can be applied only to tertiary amides with substituents that do not complex lanthanides.     

nBu4NI-catalyzed oxidative amidation of aldehydes with tertiary amines

An efficient oxidative coupling protocol for amide formation has been developed. Various tertiary amines and aromatic aldehydes were oxidized to their corresponding tertiary amides in moderate to good yields in the presence of a simple nBu₄NI-catalyst.     

Direct arylation of tertiary amines via aryne intermediates using diaryliodonium salts

With a strategy by using diaryliodonium salts as the precursors of benzynes, direct N-arylation of tertiary amines with diaryliodonium salts was reported. Thus, the desired aromatic tertiary amines with a wide range of substituents were synthesized in moderate to excellent yields of 55–91%.     

Regioselective Insertion of o‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines

o‐Carboryne can undergo α‐C? H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C? H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes.     

Kinetics and mechanism of tertiary amine‐catalyzed cleavage of N′‐morpholino‐N‐(2′‐methoxyphenyl)phthalamide: Kinetic evidence for the presence of a reactive intermediate on the reaction path

Pseudo‐first‐order rate constants (k_obs) for tertiary amine (DABCO and Me₃N) buffer‐catalyzed cyclization of N′‐morpholino‐N‐(2′‐methoxyphenyl)phthalamide ( 1 ) to N‐(2′‐methoxyphenyl)phthalimide ( 2 ) reveal saturation (nonlinear) plots of k_obs versus [Buf]_T (total tertiary amine buffer concentration) at a constant pH. Such plots at different pH have been attributed to the presence of a reactive intermediate (T^?) formed by tertiary amine buffer‐catalyzed intramolecular nucleophilic addition of the secondary amide nitrogen to the carbonyl carbon of the tertiary amide group of 1 . © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 263–272, 2010     

Electron Capture Gas Chromatography of Tertiary Amines After a Demethylation Reaction to Secondary Amines

Abstract

A gas chromatographic method for the determination of tertiary amines in micro- and nanogram amounts is presented. The tertiary amine is reacted with ethyl chloroformate to form a urethan, which is cleaved to a secondary amine. This is transformed to heptafluoro-butyramide, which makes quantitative determination with electron capture detection possible. The yields of the secondary amines for two tertiary amines were 60 and 75%. By use of internal standard technique in the entire reaction recoveries of 97.6 ± 2.2% at the 100 μg level and 100 ± 4% at the 200 ng level were obtained.     

A C=O⋅⋅⋅Isothiouronium Interaction Dictates Enantiodiscrimination in Acylative Kinetic Resolutions of Tertiary Heterocyclic Alcohols

A combination of experimental and computational studies have identified a C=O???isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. This discrimination was exploited in the isothiourea‐catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols (38 examples, s factors up to >200). The reaction proceeds at low catalyst loadings (generally 1 mol %) with either isobutyric or acetic anhydride as the acylating agent under mild conditions.     

Sulfinylnitriles: Sulfinyl–Metal Exchange–Alkylation Strategies

Adding organolithiums, Grignard reagents, or zincates to sulfinylnitriles triggers a facile sulfinyl–metal exchange to afford N‐ or C‐metalated nitriles. Sulfinyl–magnesium exchange–alkylations efficiently install quaternary and tertiary centers, even in the case of tertiary sulfinylnitriles that contain a highly acidic methine proton. α‐Sulfinylalkenenitriles afford moderately nucleophilic magnesiated nitriles, and the reactivity can be dramatically increased by conversion to the corresponding magnesiates. The sulfinyl‐metal exchange is extremely fast, proceeds efficiently with quaternary, tertiary, and vinylic α‐sulfinylnitriles, and exhibits an exceptional functional group tolerance in nitrile alkylations.