Letters in Organic Chemistry - Volume 3, Issue 1, 2006

Acetylenic coupling reactions allow for construction of a wide variety of redox-active extended tetrathiafulvalenes (TTFs) from simple acetylenic dithiafulvene building blocks. This highlight covers the synthesis of such acetylenic TTF scaffolds with oligoyne, di-, tri-, or tetraethynylethene cores.

The formation of 1-acetyl-6-methyl-8-hydroxy-5,6,7,8-tetrahydroindolizine (3) from 3-methyl-4-(3- acetylpyrrol-1-yl)butanal (2), coming from the rhodium catalyzed hydroformylation of 2-methyl-3-(3- acetylpyrrol-1-yl)prop-1-ene (1), is reported. Evidences for both the complete diastereoselective cyclization of 2 and the configuration determination in 3 via 1H, 13 C and IR spectra are reported.

An efficient method for selective cleavage of silyl ethers mediated by SbCl3 in the presence of a number of function groups was described and the primary silyl ethers were hydrolized in the presence of the secondary ethers. The desilyl reaction took much longer time in dry solution than in wet.

We describe an easy and convenient procedure for palladium-catalyzed Heck arylation of disubstituted olefins via microwave irradiation. This method of synthesis produces trisubstituted olefins under phosphane-free conditions and in very short times.

The synthesis of pyrrole-based semipeptidic mimic of neuropeptide neurotensin (8-13) [NT(8-13)] is described. The design of this NT mimic is based on substitution of indole by a pyrrole nucleus.

Aluminumdodecatangstophosphate (AlPW12O40 ) as a highly water tolerant, recyclable green Lewis acid has been applied as an efficient catalyst for the synthesis of esters from long chain aliphatic and aromatic acids and alcohols in high yields. This catalyst is also selective for the esterification of primary alcohols in the presence of secondary ones.

Aryl halides and aryl triflates (triflate = trifluoromethanesulfonyl) are coupled with N-compounds to give the corresponding arylamines or arylhydrazines in the presence of a palladium catalyst, a suitable ligand, and a base. Catalyst systems consisting of palladium (II) and BINAP or triphenylphosphine are generally effective for the amination of a wide range of aryl halides and aryl triflates with anilines and hydrazines.

The regioselective 1-O-deacetylation of peracetylated carbohydrates with ammonium acetate in DMF (or a mixed solution of tetrahydrofuran and methanol) is described. It offers a facile and efficient way to prepare O-acetylpyranosides presenting one free hydroxyl group at the anomeric position.

Several chalcones are reduced directly to the corresponding saturated alcohols, in a catalytic transfer hydrogenation process, by use of the ammonium formate/palladium on carbon system in very good yields.

1,2-O-Isopropylidene-α-D-xylofuranose has been used as a chiral protecting group of the formyl group of 2-bromobenzaldehyde, in which it acts as a resolving agent leading to separable diastereoisomers when a new stereocenter is created by substitution of bromine by a 2,3-dihydroxypropyl chain. These separated diastereoisomers were cyclised to furnish the target nucleoside analogues of d4T as an isochroman.

We report herein a new and efficient four-step method for the stereoselective conversion of (-) diethyl (D)- and (+) diethyl (L)-tartrate into diethyl (2S,3S)-(+)-2,3-epoxysuccinate and diethyl (2R,3R)-(-)-2,3- epoxysuccinate respectively. We also applied this synthetic method to prepare a C-2 symmetric epoxide, a key chiral intermediate, employed in the total synthesis of natural products.

The molecular recognition properties of a novel calix[4]arene receptor fixed in a 1,3-alternate conformation bearing two dipyridyl moieties towards organic molecules containing hydroxylic (phenolic or alcoholic) or amino functionalities have been investigated by 1H NMR spectroscopy in CDCl3. The novel receptor selectively recognizes by hydrogen bonding only molecules having two OH phenolic groups.

A facile synthesis of the title compound has been developed starting from a homoallylic alcohol that can be conveniently prepared from (R)-cyclohexylidene glyceraldehyde. The key features of the synthesis were its operational simplicity and the use of inexpensive compounds.

A one-pot solvent free Wittig procedure was suggested for fast and high efficient preparation of alkyl oxindolideneacetates a-h by reaction of isatin derivatives, triphenylphosphine, alkyl bromoacetate and morpholine.

Induced circular dichroism (ICD) was observed in binaphthyl amides of chiral primary amines. The CDs changed to split curves centered at 225 nm after N-methylation. The calculated screw senses of the two naphthyl groups accorded with those expected from their exciton chiralities, indicating a possible application for determination of absolute configuration.

Methyl prolinate and benzyl prolinate were used as secondary amine nucleophiles in palladium catalysed aminocarbonylation of iodo-aromatics and iodo-alkenes. A mixture of 2-oxo-carboxamide and carboxamide type derivatives or pure carboxamides can be obtained by using iodo-benzene or iodo-alkenes as substrates, respectively. The aminocarbonylation of iodo-alkenes in [bmim][PF6] ionic liquid was also carried out.

A survey of bases for inducing a Dieckmann cyclization of 2-acylaminobenzoates to give 4- hydroxy-2-quinolinones revealed that hindered non-nucleophilic bases were optimal. However, for sterically demanding substrates sodium hydride performed better. A tandem Michael-Dieckmann reaction for the construction of 4-hydroxy-2-quinolinones is also presented. This methodology is utilized as a key step in the synthesis of Read More

We described, herein, the preparation of new vinyldiazoacetic acid esters of carbohydrate acetonides (5b-g) in good to moderate yields. The key step of this procedure is the elimination reaction performed with α- diazo-β-hydroxy esters 4a-h by using trifluoroacetic anhydride and triethylamine as reagents. This methodology has some advantages over that one described in the literature (POCl3) for the preparation Read More