Chemoselective hydrolysis of terminal isopropylidene acetals in acetonitrile using molecular iodine as a mild and efficient catalyst

A simple, mild and efficient method for deprotection of acetonides in the presence of molecular iodine is described. Acid labile protecting groups such as PMB, OMe, OBn, allyl and propargyl are compatible with the reaction conditions, while TBS, TBDPS, TMS and THP ethers were unstable under the same conditions.     

Convenient preparation of tert-butyl esters

A general method is presented for the preparation of tert-butyl esters by the gentle warming of the carboxylic acid in the presence of excess of tert-butyl acetoacetate and a catalytic amount of acid. This method generates only low pressures, and is therefore suitable for laboratory scale pressure glassware.     

Direct conversion of aldehydes to acyl azides using tert-butyl hypochlorite

A general method, for the direct conversion of aldehydes to acyl azides using tert-butyl hypochlorite and sodium azide is described. The method is simple and occurs under mild conditions.     

Efficient indoles and anilines syntheses employing tert-butyl sulfinamide as ammonia surrogate

tert-Butyl sulfinamide is an ammonia equivalent for the palladium-catalyzed amination of aryl bromides and aryl chlorides. Using these amine derivatives, it has been observed that indoles and anilines with sensitive functional groups can be readily prepared. This surrogate has also been used for the synthesis of indoles from 2-halophenols using palladium catalyzed cross coupling reaction as the key step.     

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.     

Direct conversion of tert-butyl 2-hydroxyalkyl sulfides to 1,3-oxathiolanes

tert-Butyl 2-hydroxyalkyl sulfides, prepared by reaction of epoxides with 2-methylpropane-2-thiol, are converted directly to 1,3-oxathiolanes upon treatment with pivalaldehyde and boron trifluoride diethyl etherate in the presence of thioanisole.     

Efficient cleavage of carboxylic tert-butyl and 1-adamantyl esters, and N-Boc-amines using H2SO4 in CH2Cl2

A new procedure for the deprotection of carboxylic tert-butyl and 1-adamantyl esters, and N-Boc-amines using H₂SO₄ in CH₂Cl₂ is described. The proposed method is simple, cheap, eco-friendly and represents a valid alternative to existing ones, with special significance in large scale applications.     

Reversal of diastereoselection in the addition of Grignard reagents to chiral 2-pyridyl tert-butyl (Ellman) sulfinimines

Addition of Grignard reagents to chiral tert-butyl sulfinimines derived from pyridine 2-carboxaldehyde affords protected 2-pyridyl amines in high yields and diastereoselectivities. The sense of chiral induction is opposite to that predicted via a chelation-controlled transition state.     

An efficient protocol for the synthesis of quinoxaline derivatives at room temperature using molecular iodine as the catalyst

The use of molecular iodine as the catalyst for a one-pot synthesis of quinoxaline derivatives at room temperature is reported.     

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).     

Phase equilibrium measurements for systems containing propanenitrile with tert-butyl ethyl ether and C4-hydrocarbons

A static total pressure apparatus was used to measure isothermal VLE for systems containing propanenitrile +n-butane (322.02 K), +1-butene (312.55 K), +2-methylpropane (307.85 K) and +2-methylpropene (312.59 K). Vapour liquid equilibrium (VLE) for propanenitrile + tert-butyl ethyl ether (ETBE) was measured both with the static total pressure apparatus at 312.85 K and 358.32 K and with a glass circulation still apparatus at 102.6 kPa and 65.2 kPa. The system of propanenitrile + ETBE evidenced azeotropic behaviour.     

A mild, efficient, and selective deprotection of tert-butyldimethylsilyl (TBDMS) ethers using dicationic ionic liquid as a catalyst

Selective deprotection of alkyl TBDMS ether in the presence of phenolic TBDMS ether using dicationic ionic liquid [tetraEG(mim)₂][OMs]₂ as a homogeneous catalyst showed significant catalytic activity in methanol at ambient temperature to produce respective alcohol in excellent yield. The present environmentally benign catalytic system is found to be very convenient, fast, high yielding, and clean method for selective desilylation of alkyl silyl ethers even in the existence of other sensitive organic functional groups such as aldehyde, methoxy, and acetate were also achieved.     

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.     

Reaction of tert-butyl isocyanide and dialkyl acetylenedicarboxylates in the presence of 2-acetylbutyrolactone. Synthesis of functionalized α-methylene-γ-butyrolactones

Reaction of tert-butyl isocyanide with dialkyl acetylenedicarboxylates in the presence of 2-acetylbutyrolactone leads to the formation of dialkyl (E)-2-{(tert-butylamino)[2-oxo-4,5-dihydro-3(2H)-furanylidene]methyl}-2-butenedioates.     

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.     

A one-pot synthesis of 1,2,4,5-tetraarylimidazoles using molecular iodine as an efficient catalyst

Molecular iodine is a cheap, nontoxic catalyst, which acts as an efficient catalyst for the synthesis of 1,2,4,5-tetraarylimidazoles using benzoin, an aromatic aldehyde and an amine in the presence of ammonium acetate. The advantage of this method is the direct use of benzoin, which is transformed into benzil in situ and condenses further to generate the imidazole in a one-pot sequence.     

tert-Butyl isocyanide revisited as a convertible reagent in the Groebke-Blackburn reaction

tert-Butyl isocyanide can serve as the convertible reagent in Groebke-Blackburn multi-component reactions. The effective removal of the tert-butyl group from the resulting imidazo[1,2-a]azines and -azoles is achieved on a gram scale in two steps without chromatographic purification.     

Phosphine-catalyzed [3+3] annulation reaction of modified tert-butyl allylic carbonates and substituted alkylidenemalononitriles

A phosphine-catalyzed [3+3] annulation reaction of modified tert-butyl allylic carbonates with various alkylidenemalononitriles to form cyclohexenes was developed. The use of protic solvent is crucial in this reaction. When non-polar solvent, toluene or xylene, was used, only non-cyclized product was obtained.     

An unprecedented highly efficient solvent-free oxidation of alkynes to α,β-acetylenic ketones with tert-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC) was found to be highly efficient for the selective α-oxidation of internal alkynes to the corresponding α,β-acetylenic ketones, with aqueous tert-butyl hydroperoxide under mild conditions. For the first time, full conversions of alkynes were reached with excellent selectivities, and propargylic tert-butylperoxy ethers were observed and suggested as the reaction intermediates. In the case of terminal alkynes, the oxidations are sluggish and low yields ranging from 32% to 40% were obtained.     

Sulfide oxygenation by tert-butyl hydroperoxide with mononuclear (Me3TACN)Mn catalysts

Mononuclear (Me₃TACN)MnX₃ compounds, where X is Cl⁻, Br⁻, or N₃⁻, and Me₃TACN is 1,4,7-N,N′,N″-trimethyl-1,4,7-triazacyclononane, have been tested for catalyzing both sulfide oxygenation and styrene epoxidation by tert-butyl hydroperoxide (TBHP) and display turnover frequencies (TOF) up to 200 h⁻¹ at room temperature. Sulfoxides or sulfones may be produced selectively by varying reaction conditions. Product distribution from the oxygenation reactions of ethyl phenyl sulfide, 2-chloroethyl phenyl sulfide, and styrene is consistent with a mechanism involving an early single-electron transfer (SET) step.