Cobalt(II) catalyzed tosylation of alcohols with p-toluenesulfonic acid

Cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) has been found to catalyze the tosylation of both aliphatic and aromatic alcohols with p-toluenesulfonic acid (p-TsOH) in high yields in 1,2-dichloroethane under reflux (ca. 80 °C). In the case of aliphatic alcohols, secondary alcohols undergo tosylation chemoselectively in the presence of primary hydroxy groups.     

Chemoselective and scalable preparation of alkyl tosylates under solvent-free conditions

The improved method for the efficient tosylation of alcohols has been reported using two procedures (A and B). Procedure A: methanol, ethanol, benzyl alcohols, and valuable ethylene glycols can be converted into their corresponding alkyl tosylates in very fast, simple, and efficient grinding method using potassium carbonate as solid base. Other primary and secondary alcohols need to add potassium hydroxide to reaction mixture (procedure B). High selectivity of tosylation was observed for these two procedures. Scale up ability was found in this method even in 100 mmol of substrate. The present method is the example of solid-state tosylation using tosyl chloride, and is a green chemical process due to solvent-free conditions.     

Selective aerobic oxidation of allylic and benzylic alcohols catalyzed by N-hydroxyindole and copper(I) chloride

In the presence of copper(I) chloride, tert-butyl 1-hydroxy-2-methyl-6-trifluoromethyl-1H-indole-3-carboxylate acted as a catalyst for the chemoselective aerobic oxidation of allylic and benzylic alcohols. A variety of primary and secondary allylic and benzylic alcohols were oxidized into the corresponding α,β-unsaturated carbonyl compounds in good yields without affecting non-allylic alcohols.     

Treatment of alcohols with tosyl chloride does not always lead to the formation of tosylates

Treatment of substituted benzyl alcohols with tosyl chloride resulted in the formation of the corresponding chlorides, not the usual tosylates. A series of experiments demonstrated that it was possible to predict whether chlorination or tosylation would occur for substituted benzyl alcohols and pyridine methanols. Treatment of electron withdrawing group-substituted benzyl alcohols with tosyl chloride gave the corresponding chlorides in moderate yields under mild conditions, which provided a simple way to directly prepare chlorides from alcohols.     

Copper complex catalyzed asymmetric monosulfonylation of meso-vic-diols

Asymmetric desymmetrization of meso-vic-diols was performed by tosylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst. The method was successfully applied to asymmetric desymmetrization of cyclic and acyclic meso-vic-diols in high enantioselectivity with up to >99% ee.     

Facile removal of tosyl chloride from tosylates using cellulosic materials,e.g., filter paper

Excess tosyl chloride used in the tosylation of alcohols is quickly and easily removed by reacting it with cellulosic materials, e.g., filter paper, and filtering.     

Divergent synthesis of fully substituted isoxazoles and spiro-fused pyrazolin-5-ones from cyclopropyl oximes

Efficient and divergent synthesis of fully substituted isoxazoles and spiro-fused pyrazolin-5-ones is developed from cyclopropyl oximes based on selection of reaction conditions. Under Appel conditions (PPh₃/CBr₄), substituted isoxazoles were synthesized from cyclopropyl oximes via a ring-opening and intramolecular cyclization process, whereas by treatment of cyclopropyl oximes with p-toluenesulfonyl chloride in the presence of potassium hydroxide, spiro-fused pyrazolin-5-ones were obtained via tandem ketoxime tosylation and intramolecular cyclization.     

Quaternized amino functionalized cross-linked polyacrylamide as a new solid-liquid phase transfer catalyst in reduction of carbonyl compounds with NaBH4

Poly[N-(2-aminoethyl)acrylamido]trimethyl ammonium chloride resin was developed as a new polymeric phase transfer catalyst. This quaternized polyacrylamide catalyzed the chemoselective reduction of aldehydes and ketones by NaBH₄ to give corresponding alcohols in high yields under mild conditions.     

An efficient total synthesis of (−)-anamarine

An efficient synthesis of (−)-anamarine is described using d(+)-mannitol and (R)-epichlorohydrin. The synthesis is achieved starting from easily accessible d(+)-mannitol using a selective benzoylation, regioselective epoxide ring opening, a selective acetonide deprotection, tosylation and cross metathesis reaction.     

Polystyrylsulfonyl-3-nitro-1H-1,2,4-triazolide-resin: a new solid-supported reagent for the esterification of amino acids

We describe the application of the polystyrylsulfonyl-3-nitro-1H-1,2,4-triazolide-resin, readily available from the corresponding commercially available polystyryl sulfonyl chloride resin, to the solution-phase synthesis of esters from protected α-amino acids and alcohols in high yields and purity with a low level of racemisation of the amino acids. All by-products can be removed by filtration and extraction.     

A novel reaction of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) to form 2-fluoro-2-trifluoromethyl-4-alkenamide

Treatment of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) afforded N,N-diethyl-2-fluoro-2-trifluoromethyl-4-alkenamides which were formed by the Claisen rearrangement of intermediary 2-alkenyl-1-diethylamino-2,3,3,3-tetrafluoro-1-propenyl ethers. Although (E)-allylic alcohols gave two diastereomeric products in about 1:1 ratio, (Z)-allylic alcohols gave the corresponding product as a single diastereomer.     

Regio- and stereoselective synthesis of Z-vinylic tellurides from propargylic alcohols: a route to chiral Z-enynes

tert-Butyldimethylsilyl ethers of propargylic alcohols are hydrotellurated regioselectively to give 1,2-Z-vinylic tellurides. Enantiomerically pure propargylic alcohols give enantiomerically pure vinylic tellurides, which are coupled with alkynes under Pd catalysis to give enantiomerically pure allylic enynols.     

Gold-catalyzed transesterification of ortho-alkynylbenzoic acid esters: a novel protecting group for alcohols and phenols

Treatment of ortho-alkynylbenzoic acid esters with excess amounts of EtOH in the presence of a gold catalyst results in the liberation of alcohols or phenols in high yields under mild conditions. The protection of alcohols and phenols proceeds smoothly by use of ortho-alkynylbenzoic acid or ortho-iodobenzoyl chloride. Highly chemoselective deprotections are described.     

Synthesis of enantiopure azetidines: a route to new β-amino alcohols

β-Amino alcohols possessing an E vinylsilane moiety were cyclized in the presence of N-bromosuccinimide to afford diastereoisomerically pure polyfunctional azetidines. These azetidines were then transformed into enantiopure β-amino alcohols with a Z vinylic bromide moiety.     

Systematic study for the stereochemistry of the Atherton–Todd reaction

Under the Atherton–Todd reaction conditions, the stereochemistry on the reaction of H-phosphinates with different nucleophiles (e.g., amines, alcohols, phenols) was investigated. All reactions took place stereospecifically with inversion of configurations at the phosphorus centers. The reaction might proceed via a phosphoryl chloride intermediate with retention of configuration at phosphorus, followed by the attack of nucleophiles from the backside of Cl to give the substitution products with inversion of configuration at the phosphorus center. A plausible mechanism was proposed for these reactions.     

Efficient synthesis of carbonyl compounds: oxidation of azides and alcohols catalyzed by vanadium pentoxide in water using tert-butylhydroperoxide

Catalytic amount of vanadium reagent with tert-butylhydroperoxide as the oxidant was found to be an excellent oxidizing agent in aqueous medium. Vanadium pentoxide with aq tert-butylhydroperoxide readily oxidizes primary benzylic azides to the corresponding acids and secondary benzylic azides to the corresponding ketones in excellent yields. Further, vanadium pentoxide and aq tert-butylhydroperoxide combination turned out to be an effective catalyst for the oxidation of alcohols. Using vanadium pentoxide and aq tert-butylhydroperoxide primary alcohols were oxidized to the corresponding acids, whereas secondary alcohols underwent a smooth transformation to furnish corresponding ketones in excellent yields. All the oxidations are performed in water.     

One-pot synthesis of N-alkyl purine and pyrimidine derivatives from alcohols using TsIm: a rapid entry into carboacyclic nucleoside synthesis

A convenient and efficient one-pot N-alkylation of nucleobases from alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, treatment of alcohols with a mixture of purine or pyrimidine nucleobase, TsIm, K₂CO₃, and triethylamine in refluxing DMF regioselectively furnishes the corresponding N-alkyl nucleobases in good yields. This methodology is highly efficient for various structurally diverse primary alcohols.     

Halogenative kinetic resolution of β-amido alcohols: chiral BINAP-mediated SN2 displacement of hydroxy groups by chlorides with inversion of stereochemistry

A series of optically active cyclic trans-β-amido alcohols were obtained by the non-enzymatic kinetic resolution of the corresponding racemic amido alcohols using commercially available (S)-BINAP and NCS by S_N2 halogenation of the hydroxy group. The product, cis-β-amido chloride, was also obtained in optically active form with an inversion of stereochemistry.     

A simple one-pot procedure for the direct conversion of alcohols into azides using TsIm

A facile and efficient method for one-pot conversion of alcohols into azides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of NaN₃, TsIm and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF affording the corresponding alkyl azides in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.     

Diastereoselective formation of 2-fluoro-2-trifluoromethyl-3,4-alkadienamides from propargyl alcohols and hexafluoropropene-diethylamine adduct (PPDA)

Treatment of propargyl alcohols (1) with hexafluoropropene-diethylamine adduct (PPDA) affords N,N-diethyl-2-fluoro-2-trifluoromethyl-3,4-alkadienamides (2) that are produced by the Claisen rearrangement of intermediary 2-alkynyl 1-(N,N-diethylamino)-2,3,3,3-tetrafluoro-1-propenyl ethers. Starting from propargyl alcohols bearing a triple bond at the terminal position, the corresponding products (2) were formed with a high stereoselectivity.