Alkali Metal and Organo Group‐14 Element Ferrocenecarbo­selenoates: Synthesis and Structures

Lithium, sodium, and potassium ferrocenecarboselenoates were synthesized in good yields by the reaction of ferrocenoyl chloride with the corresponding metal selenides. In air, the saltsquickly oxidized to give diferrocenoyl diselenide. The salts readily reacted with alkyl and organo‐germanium, ‐tin and ‐lead halides to give the corresponding Se‐alkyl and Se‐organo Group‐14 element ferrocenecarboselenoates [(FcCOSe)_xMPh_4–x (M = Ge, Sn, Pb; x = 1–3) in moderate to good yields. In contrast, the reaction of the sodium and potassium salts with trimethylsilyl chloride led to O‐trimethylsilyl ferrocenecarboselenoate FcCSeOSiMe₃. Treatment of the O‐silyl ester with RbF and CsF led to rubidium and cesium ferrocenecarboselenoates, respectively, in good yields. The structures of FcCOSetBu, (FcCOSe)₂SnPh₂, and FcCOSePbPh₃ were revealed by X‐ray molecular structure analysis.     

Synthesis and some Reactions of Alkali Metal Carbamotelluroates

Sodium and potassium carbamotelluroates [M(R₂NCOTe), M = Na, K, Rb, Cs] were synthesized in moderate to good yields by reacting carbamoyl chloride with the corresponding alkali metal tellurides. The salts readily reacted with trimethylsilyl chloride to form O‐trimethylsilyl carbamotelluroate (R₂NCTeOSiMe₃), which further reacted with RbF and CsF to lead to the corresponding heavy alkali metal carbamotelluroates. These salts reacted with alkyl iodide and carbamoyl chlorides to give the corresponding Te‐alkyl carbamotelluroates and dicarbamoyl tellurides in moderate yields.     

Synthesis and reaction of selenocarbamic acid sodium and potassium salts and organo-germanium, -tin,and -lead esters

Sodium 2 and potassium selenocarbamates 3 were found to be synthesized in moderate to good yields by the reaction of carbamoyl chlorides with sodium and potassium selenides. The salts 2 and 3 reacted with alkyl halides and organo-germanium, -tin, and -lead chlorides to give the corresponding esters 7–9 in good yields.     

Carbon-carbon bond formations at the benzylic positions of N-benzylxanthone imines and N-benzyldi-1-naphthyl ketone imine

Two N-benzyl imines are designed to allow for carbon-carbon bond formations at the aminated benzylic positions. Direct benzylic arylation reactions of N-benzylxanthone imine with aryl chlorides proceed under palladium catalysis in the presence of cesium hydroxide, yielding the corresponding benzhydrylamine derivatives. Alkylation reactions of N-benzyldi-1-naphthyl ketone imine with alkyl halides in the presence of potassium tert-butoxide afford the corresponding 1-phenylalkylamines in high yields. Conjugate addition of N-benzyldi-1-naphthyl ketone imine is also described.     

O‐Triorganosilyl Carbamoselenoates – Synthesis and Reactions

A series of O‐triorganosilyl carbamoselenoates were isolated in good yields from the reaction of sodium or potassium carbamoselenoates with triorganosilyl chlorides. The O‐silyl carbamoselenoates readily reacted with RbF and CsF and with organo‐germanium, ‐tin, and ‐lead halides and gave the corresponding heavy alkali metal and Se‐substituted Group 14 organometal and carbamoselenoates in moderate to good yields.     

Cleavage of immobilized disubstituted triazenes with electrophiles: solid-phase synthesis of alkyl halides and esters

An efficient, selective cleavage of polymer-bound disubstituted triazenes with trimethylsilyl halides produces alkyl chlorides, bromides and iodides in good to excellent purities and yields. Similarly, alkyl esters are formed upon cleavage with carboxylic acids.     

Photoredox-Catalyzed Decarboxylative Bromination,Chlorination and Thiocyanation Using Inorganic Salts

Decarboxylative halogenation reactions of alkyl carboxylic acids are highly valuable reactions for the synthesis of structurally diverse alkyl halides. However, many reported protocols rely on stoichiometric strong oxidants or highly electrophilic halogenating agents. Herein, we describe visible-light photoredox-catalyzed decarboxylative halogenation reactions of N-hydroxyphthalimide-activated carboxylic acids that avoid stoichiometric oxidants and use inexpensive inorganic halide salts as the halogenating agents. Bromination with lithium bromide proceeds under simple, transition-metal-free conditions using an organic photoredox catalyst and no other additives, whereas dual photoredox-copper catalysis is required for chlorination with lithium chloride. The mild conditions display excellent functional-group tolerance, which is demonstrated through the transformation of a diverse range of structurally complex carboxylic acid containing natural products into the corresponding alkyl bromides and chlorides. In addition, we show the generality of the dual photoredox-copper-catalyzed decarboxylative functionalization with inorganic salts by extension to thiocyanation with potassium thiocyanide, which was applied to the synthesis of complex alkyl thiocyanates.     

Efficient synthesis of β-halogeno protected l-alanines and their β-phosphonium derivatives

Ring opening of oxazolines, prepared from l-serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of triphenylphosphine by the bromo or iodo derivatives led to the phosphonium salts bearing a free acid function in 95% yield, without racemization. The efficiency of this synthesis was demonstrated by the preparation of these phosphonium salts in excellent overall yields, by a one-pot procedure starting from the oxazoline.     

Solid‐State Emissive Aroyl‐S,N‐Ketene Acetals with Tunable Aggregation‐Induced Emission Characteristics

N‐Benzyl aroyl‐S,N‐ketene acetals can be readily synthesized by condensation of aroyl chlorides and N‐benzyl 2‐methyl benzothiazolium salts in good to excellent yields, yielding a library of 35 chromophores with bright solid‐state emission and aggregation‐induced emission characteristics. Varying the substituent from electron‐donating to electron‐withdrawing enables the tuning of the solid‐state emission color from deep blue to red.     

An Efficient Friedel–Crafts/Oxa‐Michael/Aromatic Annulation: Rapid Access to Substituted Naphtho[2,1‐b]furan,Naphtho[1,2‐b]furan,and Benzofuran Derivatives

Substituted naphthofurans and benzofurans are easily accessible by treatment of naphthols/substituted phenols with nitroallylic acetates through a substitution–elimination process promoted by cesium carbonate. Reactions between naphthols and aromatic/heteroaromatic‐substituted nitroallylic acetates gave the desired functionalized naphthofurans in high to excellent chemical yields (14–97 %). On the other hand, treatment of phenol derivatives (i.e., 3‐dimethylamino‐, 3‐methoxy‐, and 3,5‐dimethoxyphenol) with various nitroallylic acetates afforded the corresponding benzofurans in moderate to good chemical yields (24–91 %). The reaction proceeded through an interesting Friedel–Crafts S_N2′ process followed by intramolecular oxa‐Michael cyclization and subsequent aromatization. A plot of log (k/k_H) against Hammett constants σ_p showed satisfactory linearity with a positive ρ value, indicating that the initial Friedel–Crafts‐type S_N2′ process constituted the rate‐determining step. This methodology has been applied to the synthesis of various novel C₂ and C₃ symmetric bis‐ and trisfurans by using catechol and phloroglucinol as the nucleophilic partners. The reactivity decreased when alkyl‐substituted nitroallylic acetate systems were used. This might be related to the decreased electrophilic character of these substrates.     

Synthesis of a new palladium salt using N‐benzyl DABCO chloride and its application in Suzuki reaction

A palladium catalyst was synthesized using N‐benzyl DABCO chloride and palladium chloride. The structure of this catalyst was characterized and then the catalyst was used in Suzuki cross‐ coupling reaction of different aryl halides with arylboronic acids. All substrates afforded the corresponding products in good to high yields in the presence of low amounts of the catalyst. Under the heating conditions employed, cheaper and more available aryl chlorides gave relatively high yields in the Suzuki reaction. Copyright © 2012 John Wiley & Sons, Ltd.     

Expedient Iron‐Catalyzed Coupling of Alkyl,Benzyl and Allyl Halides with Arylboronic Esters

While attractive, the iron‐catalyzed coupling of arylboron reagents with alkyl halides typically requires expensive or synthetically challenging diphosphine ligands. Herein, we show that primary and secondary alkyl bromides and chlorides, as well as benzyl and allyl halides, can be coupled with arylboronic esters, activated with alkyllithium reagents, by using very simple iron‐based catalysts. The catalysts used were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)₃] with no added co‐ ligands. In the former case, preliminary mechanistic studies highlight the likely involvement of iron(I)–phosphine intermediates.     

Lewis Acid Induced α-Alkylation of Carbonyl Compounds

Carbonyl compounds undergo α-alkylation via the corresponding silyl enol ethers using S_N1 active alkyl halides or acetates in the presence of Lewis acids. This methodology extends the scope of carbonyl chemistry considerably, since S_N1 active alkylating agents are generally base sensitive and therefore unsuitable for reactions with enolate anions or nitrogen analogs. A prime example is the α-tert-alkylation of aldehydes, ketones and esters.     

Retro-ene reaction I: Reaction of N-hydroxymethylsaccharin with benzoyl chlorides and alkyl halides

N-Benzoylsaccharins, N-(saccharinylmethyl) benzoates and N-alkylsaccharins were synthesized from N-hydroxymethylsaccharin and the corresponding benzoyl chlorides or alkyl halides under different conditions. The reaction mechanisms are also discussed.     

Potential N‐Heterocyclic Carbene Precursors in the Palladium‐Catalyzed Heck Reaction

A novel 1‐(cyclobutylmethyl)‐substi‐tuted imidazolidinium/benzimidazolium salts as N‐heterocyclic carbene (NHC) precursors were successfully synthesized and characterized by ¹H NMR, ¹³C NMR, IR, and elemental analysis techniques. These compounds were easily prepared from the reaction of N‐alkyl imidazoline/N‐alkyl benzimidazole with bromomethylcyclobutane in high yields. The in situ formed catalytic system derived from the NHC precursor and Pd(OAc)₂ was used in the Heck reaction between aryl halides and styrene with potassium hydroxide in water. The corresponding Heck products were obtained in good yields. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:77–83, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21065     

Design and synthesis of some new thiophene and 1,3,4-thiadiazole based heterocycles

Abstract

The reaction of 3-oxopropanenitriles with phenyl isothiocyanate in DMF containing KOH afforded the corresponding potassium salts. The latter salts were converted into ketene N,S-acetals upon acidification with hydrogen chloride. The reaction of the ketene N,S-acetals with 2-bromo-1-[5-methyl-1-(p-tolyl)-1H-1,2,3-triazol-4-yl]ethan-1-one or 3-(2-bromoacetyl)-2H-chromen-2-one gave novel thiophenes in good yields. Treatment of the ketene N,S-acetals with hydrazonyl halides afforded 1,3,4-thiadiazoles in good yields. The stereochemistry of the synthesized compounds was studied.     

Studies on pyrrolidinones. Synthesis of N-benzhydrylpyroglutamic acids and esters

Catalyzed N-alkylation of N,O-bistrimethylsilyl pyroglutamic acid with trimethylsilyl benzhydryl ethers yields trimethylsilyl N-benzhydrylpyroglutamates. Hydrolysis of these compounds or saponification of the methyl esters gives the corresponding acids.     

Efficient synthesis of 3,5‐functionalized isoxazoles and isoxazolines via 1,3‐dipolar cycloaddition reactions of 1‐propargyl‐ and 1‐allylbenzotriazoles

3‐Aryl‐5‐(benzotriazol‐1‐ylmethyl)‐ 10a‐f and 3‐p‐methoxyphenyl‐5‐(α‐benzotriazol‐1‐yl‐α‐ethoxymethyl)‐isoxazole (13) were prepared in high yields by 1,3‐dipolar cycloadditions of 1‐propargyl‐benzotriazole (5) and (α‐ethoxypropargyl)benzotriazole (8), respectively, with nitrite oxides 3a‐f (prepared in situ from benzohydroximoyl chlorides 2a‐f). The benzotriazol‐1‐ylmethyl moiety was further elaborated by sequential lithiation and reaction with aldehydes, alkyl halides and Michael acceptors. Similar 1,3‐cycloadditions using 1‐allylbenzotriazole (6) and 1‐(α‐ethoxyallyl)benzotriazole (7) afforded 3,5‐substituted isoxazolines 11b, f and 12 in excellent yields.     

The reaction of acetic acid 2‐selenoxo‐2H‐pyridin‐1‐yl esters with benzynes: A convenient route to Benzo[b]seleno[2,3‐b]pyridines

Benzyne and its 3,4,5,6‐tetraphenyl, 3‐ and 4‐methyl, 3‐methoxy and 4,5‐difluoro derivatives react with acetic acid 2‐selenoxo‐2H‐pyridin‐1‐yl esters 4a‐e to give benzo[b]seleno[2,3‐b]pyridines 10–15 in modest yields. The benzynes were generated by one or more of the following methods: diazotization of anthranilic acids 5a‐g with isoamyl nitrate; mild thermal decomposition of 2‐diazoniobenzenecarboxylate hydrochlorides 6a‐d treatment of (phenyl)[o‐(trimethylsilyl)phenyl]iodonium triflate (7) with tetrabutylammonium fluoride; and treatment of 2‐trimethylsilylphenyl triflates 8a‐c with cesium fluoride. In all the reactions, the corresponding 2‐(methylselenenyl)pyridines 16a‐d were also obtained suggesting that these reactions may involve selenium addition to benzyne via a SET (single electron transfer).     

New Low‐Molecular‐Mass Gelators Based on L‐Lysine: Amphiphilic Gelators and Water‐Soluble Organogelators

The new L ‐lysine alkali‐metal salts 1 – 5 (M⁺=Na⁺ and K⁺) with different alkyl groups at the N^α‐position were easily synthesized, and their hydro‐ and organogelation properties were investigated. All compounds were H₂O‐soluble, and some salts, especially the potassium salts, functioned as a hydrogenator that could gel water below 2 wt‐%. These salts also had organogelation abilities for many organic solvents.