Letters in Organic Chemistry - Volume 3, Issue 11, 2006

An asymmetric Horner-Wadsworth-Emmons (HWE) reaction of σ-symmetric 4-methylcyclohexanone (6c) and a novel HWE reagent 4a bearing O-benzylisomannide was investigated by employing Sn(OSO2CF3)2 and N-ethylpiperidine. As a result, α-methyl-a,β-unsaturated ester 7c, a tetrasubstituted alkene with an axis of chirality, was obtained in > 99% de.

An efficient and flexible asymmetric synthesis of chiral ferrocenylamines 3a-c via diastereoselective addition of organolithium compounds to chiral imines is described. High diastereoselectivity(93% de) was observed with ferrocenecarboxaldehyde imine 2b in the presence of the Lewis acids BF3oOEt2.

The first total synthesis of (+)-deoxytylophorinine has been accomplished in 6 linear steps and with 39.6% overall yield. An important feature of this synthesis is that Friedel-Craft acylation of (S)-1- benzyloxycarbonylpyrrolidine-2-acetyl chloride with phenylmethylether catalyzed with fresh anhydrous aluminum chloride to provide 2-(4-methoxyphenacyl)pyrrolidine and cleavage of the Cbz group have been proceeded in one Read More

The synthesis of six new esters derivatives of p-tert-butylcalix[4]arene in cone conformation is described. The preliminary complexing study of new compounds in the membranes of ion selective electrodes (ISEs) indicated Na+ selectivity for compounds 6, 7 and 8. The X-ray crystal structure of compound 6 is presented.

A novel method for a synthesis of N-methyl 2-substituted indole was developed by a palladium catalyzed cross-coupling reaction of an enol triflate derived from the N-methyl-2-indolone with (alkenyl)tributylstannanes and acetylenes in good to excellent yields. In addition, the enol triflate derived from lactam exhibited less reactivity with respect to cross-coupling reactions as compared with those of the enol triflates of 2-coumaran Read More

A simple and efficient approach to the synthesis of the new chiral hexahydropyrrolo [1',2',5':3,4,5]thiazolo[3,4-c]oxazol-1-one ring system is reported. Infrared spectroscopy, quantum-chemical calculations and X-ray analysis allowed the stereochemistry assignment of (2aS,4aR,6aR)-2a,3,4,4a,6,6ahexahydropyrrolo-[ 1',2',5':3,4,5]thiazolo[3,4-c]oxazol-1-one.

The base-mediated heterocyclization of alkyl N-(c-3,t-4-dibromocyclohex-1-yl)carbamates (5, 7, 10), or N-(c-3,t-4-dibromocyclohex-1-yl)-2,2,2-trifluoroacetamide (12) is a convenient method for the synthesis of the 7-azabicyclo[2.2.1]heptane derivatives. For instance, the reaction of t-butyl N-(c-3,t-4-dibromocyclohex-1- yl)carbamate (5) with sodium hydride in DMF at room temperature provided (1RS,2SR,4SR)-2-bromo-7-[(t Read More

Six AChE reactivators with propane linker were synthesized using modification of currently known synthetic pathways. Their potency to reactivate AChE inhibited by nerve agent tabun and insecticide paraoxon was tested in vitro. The reactivation efficacies of pralidoxime, HI-6, obidoxime and six synthesized reactivators were compared. According to the results obtained, three reactivators seem to be promising against paraox Read More

N-Alkyl and N-aryl 5-substituted oxazolidinones 12-19 were prepared in good to excellent yields by reaction of N-alkyl and N-aryl 1,2-amino alcohols 3-10 with S,S-dimethyldithiocarbonate (11) in the presence of solid NaOH under SL-PTC conditions. The procedure is particularly suitable for scale-up the process involving the use of cheap and ecosafe reagents under mild reaction conditions.

The oxidation of hydrobenzoins to the corresponding benzils was carried out in CH2Cl2 by CrO3- NH4Cl in excellent yield at room temperature under ultrasound irradiation.

A novel procedure is described for the formation of methyl and vinyl substituted oxacycle fused uracil derivatives. Ring closing metathesis and enyne metathesis of dienes and enynes respectively proceeded smoothly under nitrogen atmosphere at room temperature in the presence of well defined catalyst (first generation Grubbs' catalyst) to afford the substituted oxepin derivatives in good yields. The substrates were prepa Read More

A series of multicomponent reactions has been carried out using HClO4-SiO2 as a versatile catalyst. A series of medicinally important heterocyclic core structures have been prepared under solvent-free reaction conditions. In all cases, the reaction conditions were very simple and high yielding.

Electrochemical reduction of diselenides allows the formation of selenide anions which react with different chloroformates yielding the corresponding selenocarbonates in moderate to very high yields. The reaction is general and prevents the use of further reagents or drastic reaction conditions. Moreover the use of labile or air sensitive precursors such as selenides is avoided.

An efficient and straightforward approach towards the synthesis of a-amino acid-derived cyclic amides was developed. A series of cyclic amides of various natural amino acids were obtained in excellent yields under mild conditions. The obtained compounds could be efficiently used as ligands for affinity chromatography of enzymes.

The palladium(0)-catalyzed heteroannulation of 2,2'-diphenol and the biscarbonate of butenediol afforded quantitatively rac-(SA,6R)-6-vinyl-6,7-dihydrodibenzo[e,g][1,4]dioxocine. The use of chiral ligands gave this unique stereoisomer with ee up to 30%.

In this communication a convenient and novel method for the synthesis of tetrathiafulvalenecarbohydrate (TTF) derivatives from anhydro triflyl-, iodo- and bromo-sugars is described.

Application of microwave irradiation to Meldrum's acid and aryl aldehydes, both adsorbed on neutral alumina, furnished efficiently the corresponding Knoevenagel condensation products remarkably fast.

FeCl3·6H2O and Fe(NO3)3·9H2O supported on silica gel efficiently catalyze deprotection of bisulfite addition products to their corresponding aldehydes and ketones at room temperature under solvent-free conditions. Chemoselective deprotection of bisulfite addition products can be successfully achieved in the presence of trimethylsilyl ethers, oximes, acylals and acetals.