Synthesis of azamacrocycles via a Mitsunobu reaction

Reaction of pernosylated diethylenetriamine and 2-substituted propane-1,3-diols in dry THF in the presence of triphenylphosphine and diisopropyl azodicarboxylate gives the corresponding protected 9-substituted 1,4,7-triazacyclodecanes. The Mitsunobu reaction was also used in the preparation of 3-substituted 1,5,9-triazacyclododecanes and macrocyclic pyridine derivatives.     

Desilylation procedure via a naphthalene-catalysed lithiation reaction

The reaction of silyl protected alcohols, amines and thiols with lithium powder and a catalytic amount of naphthalene, in THF, at 0 °C led, after hydrolysis, to the recovery of the free alcohols, amines and thiols in very good yields. At least a phenyl group was required in the silyl protecting group for the success of the reaction. Some polyfunctionalised starting materials have successfully been deprotected. The stereochemical outcome of the deprotection of a silylated chiral secondary alcohol has also been studied and no racemization was observed. The process has shown to be a good alternative to the acid-catalysed desilylation procedures, the latter being not useful for the deprotection of some silylated tertiary alcohols.     

Isoquinolone derivatives via a furan recyclization reaction

A new approach to the synthesis of isoquinolone derivatives has been developed. It is based on the protolytic recyclization of amides of 2-carboxybenzylfurans. It was shown that the reaction proceeds via formation of allylic alcohols of isoquinolone series, which under acidic conditions undergo isomerization into the corresponding ketones. A new condensed heterocyclic system of furo[2′,3′:3,4]cyclohepta[1,2-c]isoquinolin-8(6H)-one has been synthesized.     

Desymmetrisation of a meso-N-hydroxyimide via a chiral Lossen reaction

N-[(1S)-10-Camphorsulphonyloxy]norborn-5-ene-endo-2,3-dicarboximide 2 underwent a Lossen type reaction with dicyclohexylmethylamine to furnish endo-2-methoxycarbonyl-endo-3-(methoxycarbonylamino)norborn-5-ene 3, in 84% yield and 33% e.e. (by NMR).     

Synthesis of stable ketenimines via a four-component reaction

Abstract  

An efficient one-pot synthesis of ketenimine derivatives is described. It involves a four-component reaction between benzylamines, 2,2-dichloroethanoyl chloride, alkyl isocyanide, and dialkyl acetylenedicarboxylates under mild conditions at ambient temperature.     

Synthesis of epothilones via a silicon-tethered RCM reaction

[reaction: see text] A short synthesis of epothilone B and D is reported. The key step for generating the C12-13-trisubstituted Z-double bond uses a ring-closing metathesis reaction of a disiloxane to form a nine-membered silicon-tethered ring.     

Asymmetric synthesis of naproxen via a pinacol-type reaction

An asymmetric pinacol-type rearrangement was used in the synthesis of (S)-naproxen. The pinacol-type reaction of a vicinal diol provided an -aryl ketone which was oxidized with sodium hypochlorite in the presence of methanol to the methyl ester of naproxen.     

Efficient C-C double-bond formation reaction via a new synthetic strategy: a self-sorting tandem reaction

[reaction: see text] A novel and efficient carbon-carbon double-bond formation reaction via coupling of aryl or heteroaryl methyl ketones has been developed. A dimethyl sulfoxide-iodine-CuO system was proven to be efficient for this reaction and afforded the expected products in good yields. A new synthetic strategy, a self-sorting tandem reaction, was involved in this type of reaction and was presented for the first time.     

Synthesis of S-linked carbohydrate analogues via a Ferrier reaction

In this work, the synthetic utility of the Ferrier reaction to access S-linked disaccharides and S-linked glycoamino acids has been probed. Significantly, entry to a range of 1,4- and 1,6-S-linked disaccharides has been achieved using glycals derived from glucose and galactose, and sulfur containing coupling partners derived from methyl α-d-glucopyranoside. Access to S-linked glycoamino acids and glycopeptides has also been achieved using protected cysteine and homocysteine coupling partners within the Ferrier reaction. Functionalisation of the Ferrier products, for example, via dihydroxylation using OsO₄ or amino acid coupling, and deprotection of the targets have also been achieved. In this way, entry to materials of interest as mimics of biologically interesting disaccharides and glycopeptides has been realised, including targets derived from rare sugars such as talopyranose and gulopyranose.     

Synthesis of substituted thiacrown ethers via a bromoalkoxylation reaction

A variety of alkyl- or phenyl-substituted thia-crown ethers were prepared in two or three steps via bromoalkoxylation reactions of olefins. Dialkyl- and phenyl-substituted mono-and dithia-crown ethers were obtained as single compounds, whereas monoalkyl-substituted derivatives were a mixture of two positional isomers reflecting the isomeric mixture formation in the bromoalkoxylation reaction.     

One-step labelling of sphingolipids via a scrambling cross-metathesis reaction

The alkyl chain in the backbone of sphingosine derivatives can be exchanged with functionalised (labelled) side chains in a single step under cross-metathesis reaction conditions.     

Stereospecific synthesis of dienones via a torquoselective retro-Nazarov reaction

[reaction: see text] Enol ethers are cleaved via a three-step sequence involving cycloaddition with dichloroketene, ring expansion with diazomethane, and a base-mediated retro-Nazarov reaction. The latter conrotatory process proceeds torquoselectively and stereospecifically in accord with theoretical predictions.     

N-Heterocyclic carbene-catalyzed synthesis of acetyltributylcitrate via a transesterification reaction

A new methodology for the synthesis of a green plasticizer acetyltributylcitrate through a transesterification reaction was developed. Under the catalysis of alkyl-substituted imidazol-type N-heterocyclic carbenes, tributyl citrate can react with vinyl acetate smoothly to give ATBC in high yield.     

Synthesis of aliphatic isocyanates via a two-phase Hofmann reaction

A convenient method of preparing aliphatic isocyanates via a two-phase Hofmann reaction using a phase transfer catalyst is described.     

Rearrangement in the mass spectrometer via a 3,3,1-bicyclic reaction path

The fragmentation of some azoacylals showed a 3,3,1 bicyclic rearrangement which could be demonstrated by a deuterium labelling study.     

Arylation of pyridine N-oxides via a ligand-free Suzuki reaction in water

We report a practical and highly efficient protocol for the arylation of pyridine N-oxides with arylboronic acid through palladium-catalyzed Suzuki reaction in water.This ligand-free Suzuki reaction is performed in the presence of diisopropylamine and gives 2-or 3-arylated pyridyl N-oxide derivatives in good to excellent yields within 1 h.