Iridium catalysed alkylation of tert-butyl cyanoacetate with alcohols under solvent free conditions

Ir-catalysed alkylation of tert-butyl cyanoacetate with a range of substituted benzyl and heteroaryl alcohols under solvent free conditions afforded the corresponding monoalkylated products in moderate to high yields.     

Stereoselective cycloaddition of 1-glucosyl-1,3-butadienes with tert-butyl 2H-azirine-3-carboxylate, glyoxylates and imines

Glucosyl dienes 1 have been reacted with the achiral 2H-azirine 4 and with glyoxylates, forming fused structures of type 5 and disaccharide-like compounds 7 with good to excellent selectivity. Glucosyl dienes 1 participated as dienophiles in reactions with Schiff bases derived from anilines forming isoquinolines 10 and 11. The diastereoselectivity of this reaction is poor.     

CuCl catalyzed oxidation of aldehydes to carboxylic acids with aqueous tert-butyl hydroperoxide under mild conditions

Oxidation of aldehydes to the corresponding carboxylic acids can be performed highly efficiently at room temperature with 70% tert-butyl hydroperoxide (in water) in the presence of a catalytic amount of easily available ligand free CuCl in acetonitrile as solvent under very mild conditions. This oxidation protocol works well for various aldehydes including aliphatic aldehydes and aliphatic dialdehydes.     

A new and highly efficient water-soluble copper complex for the oxidation of secondary 1-heteroaryl alcohols by tert-butyl hydroperoxide

The water-soluble copper complex generated in situ from CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), has been revealed as a highly efficient and selective catalyst for the oxidation of secondary 1-heteroaryl alcohols to the corresponding heteroaromatic ketones with aqueous tert-butyl hydroperoxide, under mild conditions. The catalytic system is compatible with different heterocycles such as pyridines, pyrroles, indoles, thiophens, furans, thiazoles, and imidazoles.     

Homo and block copolymers of tert-butyl methacrylate by atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) of tert-butyl methacrylate (tBMA) was investigated using cuprous bromide with different ligands, solvents, deactivators, etc. The polymerization in bulk and diphenyl ether solvent system performed using Cu(I)Br complexed with N, N, N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) catalyst in conjunction with 2-bromopropionitrile as an initiator at room temperature showed a curvature in the first-order kinetic plot. The controlled polymerization in methanol solution resulted in slower rate of polymerization and lower molecular weights. Well-defined diblock copolymers of PSt-b-PtBMA synthesized by polystyrene bromo macroinitiator (PSt-Br) with Cu(I)Cl/PMDETA catalyst system yielded predetermined molecular weights and lower polydispersities. Otherwise, the Cu(I)Br/PMDETA catalytic system showed an inefficient polymerization of tert-butyl methacrylate with lower molecular weights and higher polydispersities. Subsequent hydrolysis of the homopolymer refluxed in dioxane with addition of HCl afforded well-defined poly(methacrylic acid).     

Boron trichloride as an efficient and selective agent for deprotection of tert-butyl aryl sulfonamides

A fast, mild and selective method for deprotection of tert-butyl aryl sulfonamides utilizing BCl₃ as deprotection reagent has been developed. A variety of tert-butyl aryl sulfonamides used under these conditions gave the corresponding primary sulfonamides in high yields. The method does not cleave methoxy groups and prevents incorporation of tert-butyl groups onto electron-rich aromatic rings.     

Solution behavior of 4-arm poly(tert-butyl acrylate) star polymers

This paper reports the synthesis of 4-arm poly(tert-butyl acrylate) stars of different molar masses up to 10⁶ g/mol by the “core-first” method using ATRP. All obtained stars have a monomodal and narrow molar-mass distribution (<1.2).The dilute-solution properties of these star polymers were investigated in good solvents (tetrahydrofuran and acetone). Gel permeation chromatography and dynamic and static light scattering were used to measure the hydrodynamic properties including intrinsic viscosity [η], radius of gyration R_g, hydrodynamic radius R_h, second virial coefficient A₂ and diffusion coefficient D₀. These data were used to establish relationships between these parameters and the molar mass of 4-arm poly(tert-butyl acrylate) stars. The branching parameters g and g′ and the shape factor ρ were calculated for all obtained star polymers.     

Alkylation of 4-picolinium salts under phase transfer conditions

Alkylation of 1-ethyl-4-methylpyridinium bromide by allyl, benzyl and propargyl chlorides has been effected under conditions of phase transfer catalysis in a solid phase-liquid system (K₂CO₃-CHCl₃). Using the example of alkylation by allyl chloride, the effect of the concentration and the nature of the catalyst, the concentration of the base, and the temperature on the yield of mono-, di-, and trisubstituted products has been studied. The reactivity of the alkyl chlorides increases in the order allyl < benzyl < propargyl. When the reaction is carried out in a liquid—liquid system (25% aqueous NaOH-CHCl₃) the Br- anion of the starting material is replaced by Cl^–, in contrast to the K₂CO₃-CHCl₃ system.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 520–524, April, 1989.     

A novel practical cleavage of tert-butyl esters and carbonates using fluorinated alcohols

Thermolytic cleavage of t-butyl esters and t-butyl carbonates was accomplished using TFE (2,2,2-trifluoroethanol) or HFIP (hexafluoroisopropanol) as solvent. Thus, a practical method to cleanly convert t-butyl esters and carbonates into the corresponding carboxylic acids, decarboxylated products, or alcohols in nearly quantitative yields was developed. The product is recovered by a simple solvent evaporation. The practicality of this methodology was demonstrated on alkyl, aryl, and heteroaromatic esters.     

CuCl catalyzed selective oxidation of primary alcohols to carboxylic acids with tert-butyl hydroperoxide at room temperature

Direct oxidation of primary alcohols to the corresponding carboxylic acids is performed highly efficiently at room temperature with anhydrous tert-butyl hydroperoxide in the presence of a catalytic amount of easily available CuCl under ligand free conditions in acetonitrile. Benzylic alcohols are more reactive than aliphatic alcohols, and these benzylic alcohols are selectively oxidized to the corresponding acids in the presence of aliphatic alcohols such as 1-octanol and 1-decanol.     

Gold-catalyzed cyclization of 1-alkynyl cyclopropyl tert-butyl carbonate to construct multifunctionalized vinyl cyclopropane derivatives

A convenient new method was developed to prepare two types of vinyl cyclopropane derivatives through gold-catalyzed cyclization of 1-alkynyl cyclopropyl tert-butyl carbonates 2. Different from the previous reported 5-exo-dig route, the 6-endo-dig addition is the preferred pathway to provide six-membered cyclized carbonates. Two factors, including stereoelectronic effect and steric effect might affect the regioselectivity. Therefore, low steric aliphatic substrates afforded only six-membered isomers. The synthetic utility of compound 3 was also explored to afford a series of β-carbonyl cyclopropanol derivatives.     

Autooxidation of methylheterocycles under phase transfer catalysis conditions

The autooxidation of methyl- and dimethyl-substituted N-, S-, and O-heterocyclic compound derivatives has been studied in 1,2-dimethoxyethane—t-BuOK in the presence of 18-crown-6. Mono- and dicarboxylic acid derivatives of pyrazine, pyridine, pyrimidine, and thiophene have been synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 959–962, July, 1991.     

Benzyl and tert-butyl carbamate derivatives of 1,ω-amino acids as simple yet efficient gelators

We report the synthesis and a study of the gelation properties of a series of N-protected long-chain amino acids. Especially, benzyl and tert-butyl carbamate derivatives of 11-aminoundecanoic acid in their deprotonated form can gelate polar organic solvents and water at very low concentration (less than 5 mM). This is explained by the contribution of multiple forces—H-bond, van der Waals and ionic interactions—in the gel aggregate formation and stabilization, which is confirmed by the experimental data. Among the series of compounds investigated, only a dimer of 11-aminoundecanoic acid is capable of gelating toluene, which stems from the increased number of hydrogen bonding sites in the main aliphatic chain.     

Synthesis of phenoxypyridines under phase transfer catalysis conditions

Reactions of halopyridines with alkali metal phenoxides in a two phase liquid-solid catalytic system, rather than in a liquid-liquid phase transfer catalytic system, make it possible to prepare 2-, 3-, and 4-phenoxypyridines from unactivated bromo- or chloropyridines and 2-chloropicolines. In polyhalogenated pyridines only - and -halogen atoms undergo substitution. 7, 8-Dibromo-6-azaphenoxane has been prepared by the reaction of 2,3,5,6-tetrabromopyridine with the dipotassium salt of pyrocatechol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 24, No. 3, pp. 356–360, March, 1988.     

Reactions of metal tert-butoxides with aromatic sulfonyl chlorides. A new synthesis of di-tert-butyl ether

Di-tert-butyl ether was synthesized in good yields by the S_N reactions of lithium tert-butoxide with tosyl and p-bromobenzenesulfonyl chlorides under mild conditions.     

Ring contraction in 2,2,6,6-tetramethylpiperidin-4-one with dichlorocarbene under phase transfer conditions

The preparation of a 5-membered lactam via a postulated dichlorooxirane intermediate is described.     

A mild,copper-catalysed amide deprotection strategy: use of tert-butyl as a protecting group

Mild methods for the deprotection of organic substrates are of fundamental importance in synthetic chemistry. A new room temperature method using a catalytic amount of Cu(OTf)₂ is reported. This allows use of the tert-butyl group as an amide protecting group. The methodology is also extended to Boc-deprotection.     

Molybdenum hexacarbonyl supported on functionalized multi-wall carbon nanotubes: Efficient and highly reusable catalysts for epoxidation of alkenes with tert-butyl hydroperoxide

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)₆ supported on amines modified multi-wall carbon nanotubes, MWCNTs, is reported. The prepared catalysts were characterized by elemental analysis, scanning electron microscopy, FT-IR and diffuse reflectance UV-Vis spectroscopic methods. These new heterogenized catalysts, [Mo(CO)₆@amines-MWCNT], were used as highly efficient catalysts for epoxidation of alkenes with tert-BuOOH. These robust catalysts could be reused several times without loss of their catalytic activities.