Letters in Organic Chemistry - Volume 3, Issue 4, 2006

Formation of an aryl-carbon bond by a nucleophilic substitution is limited to activated substituted aromatics and strong nucleophiles (SN2Ar path) or to good electron donors (SRN1 process). Aryl SN1 reactions forming new Ar-C bonds have now emerged as a convenient alternative and can be easily accomplished by reaction of phenyl cations (in their triplet state) with various nucleophiles (olefins, (hetero)arenes). These cations Read More

We prepared anion receptors based on acyclic phenol-formaldehyde oligomer bearing thiourea groups. The dimer (1b) and trimer (1c) showed the binding selectivity toward chloride (Cl-) and hydrogen sulfate (HSO4 -), respectively. This selectivity will be attributed to the fit size and shape of anionic species, which favor formation of a stable host-guest complex through the multiple intermolecular hydrogen bonding.

Silphos [PCl3-n(SiO2)n], a heterogeneous phosphine reagent provides a facile and efficient method for the dehydration of aldoximes and Beckmann rearrangement of ketoximes in CH3CN at room temperature without occurrence of any deprotection reaction. Silphos also deprotects oximes in the presence of catalytic amounts of molecular bromine in excellent yields. The separation of the produced Silphos oxide is chromatogr Read More

A mild and efficient procedure for chemoselective and regioselective hydrolysis of acetonide with SbCl3 in the presence of other frequently used hydroxy protecting groups, TBDMS, TBDPS, Bz, Bn, Ac, Ts and Tr, was described. The mechanism was examined and proposed.

LiCl efficiently catalyzes cyanosilylation of various hetero-substituted ketones. α,α-Dialkoxy ketones are completely converted to silylated cyanohydrins with a substrate-to-catalyst molar ratio of 100,000 at room temperature. Acetophenones substituted by an electron-attracting group at the ortho or para position show higher reactivity than substrates with an electron-donating function.

Titanium trichloride in H2O can be reduced by Al to the corresponding low valent titanium complexes, which can reduce some aromatic aldehydes and ketones to the corresponding pinacols in 15-83% yields within 25-100 min at r.t.under ultrasound irradiation.

An immobilization of copper(I) in organic-inorganic hybrid materials catalyzed Sonogashira coupling reaction was developed. Terminal alkynes reacted with aryl iodides and aryl bromides in the presence of 3-(2-aminoethylamino)propyl functionalized silica gel immobilized copper(I) catalyst, triphenylphosphine and potassium carbonate in DMF. The reactions generated the corresponding cross-coupling products in good to exc Read More

A variety of 5-substituted-1,3,4-oxadiazole-2(3H)-thiones were prepared using microwave irradiation as energy source under solvent-free conditions. Reaction times were reduced from 5-14 h to 3-7 min affording high yields from corresponding acyl and aroyl hydrazides.

Poly-substituted quinolines are readily prepared in excellent yields via a Friedlander reaction of oaminoarylketone or o-aminoarylaldehyde with α-methylene ketones in the presence of BiCl3 under solventfree and thermal heating conditions.

Alcohols and trimethylsilyl and tetrahydropyranyl ethers are efficiently converted to their corresponding carbonyl compounds with KBrO3 in the presence of Fe(HSO4)3 and wet SiO2 in solution and under solvent free conditions.

A high yielding and fast method of Knoevenagel condensation of malononitrile and ethylcyanoacetate with various aldehydes using sodium pyruvate in aqueous media is described.

A simple and efficient synthetic method of obtaining pyridinyl substituted indeno[2,1-c]quinoline derivatives has been developed. This method involves a three-component imino Diels-Alder cycloaddition between anilines, pyridinecarboxyaldehydes and indene as the key ring forming step and subsequent treatment of obtained 5,6,6a,11b-tetrahydroindeno[2,1-c]quinolines with powdered sulfur to give corresponding indeno[ Read More

SiO2/N2O4 system was used as an efficient oxidant for the conversion of cyclic dioxalanes and dithianes to parent carbonyl compound in CH2Cl2 at room temperature. We also found Fe(NO3)3.9H2O/H3PMo12O40.xH2O could be used as a powerful oxidation complex for similar transformations at room temperature under solvent free conditions.

Reaction of allyltriphenylphosphonium bromide and Garner's aldehyde in basic media provided β- hydroxy-1,3-dienes. Similar results are described for other aliphatic and aromatic aldehydes.

Potassium iodide supported on natural phosphate in HMDS was used as a promotor in the condensation of 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose with trimethylsilylated nucleobases, under mild conditions, to provide several D-ribonucleosides.

β-Amino alcohols possessing an alkynyl functionality were converted into bicyclic compounds via a 5-exo-dig radical cyclization. One of this bicyclic product was transformed in three steps into the (2R,3S,5S)- 3-methyl-5-iso-propyl proline.

A series of 1,4- dihydropyridines derivatives have been obtained by the reaction of chalcones with dimedone in the presence of ammonium formate under solvent-free conditions. Each title compound was formed in good yield. The structure of these compounds has been thoroughly studied by X-ray crystallographic analysis.

A microwave-assisted amination reaction involving aryltrifluoroborates has been developed. This solvent-free coupling reaction is noteworthy for its experimental simplicity .

Aza-Michael additions are an easy way to prepare β-aminoesters. This reaction was investigated in the presence of catalytic amounts of bismuth (III) triflate under conventional and microwave irradiation conditions. It was shown that combination of both the catalyst and microwave irradiation under solvent-free conditions enhances the conjugate addition of amines to α,β-unsaturated esters.