One-pot synthesis of amides from aldehydes and amines via C-H bond activation.

A one-pot synthesis of amides from aldheydes with N-chloroamines, prepared in situ from amines, has been developed. Both aliphatic and aromatic aldehydes and many types of mono- and disubstituted amines are tolerant in this transformation. This cross-coupling reaction appears simple and convenient, has a wide substrate scope and makes use of cheap, abundant, and easily available reagents.

Some recent approaches to the synthesis of 2-substituted benzofurans.

In their structural multiplicity and in the extent to which they occur in nature the derivatives of benzofuran are significantly lesser than the isoelectronic analogue indoles. However, these heterocyclic compounds show a variety of pharmacological properties, and change of their structure offers a high degree of diversity that has proven useful for the search of new therapeutic agents. The broad spectrum of pharmacological activity in individual benzofurans indicates that this series of compounds is of an undoubted interest. From this point of view, synthetic methods may be of very useful aid in the production of specific structures characterized by given pharmacological qualities. Moreover from a drug discovery perspective, synthesis of chiral functionalized substituted benzofurans could be more interesting because they might constitute starting materials for the production of biologically active compounds. Taking into account the actual tendency directed toward the development of enantiomerically pure drugs, indeed there is a limited number of papers related to the preparation of enantiomers of benzofuran containing compounds, likely because of difficulties in their preparation with conventional methods. In this context, new approaches seem to expand the potentiality of the synthesis of substituted benzofurans, providing also convenient routes to enantiopure 2-substituted benzofurans.

Parallel synthesis of trisubstituted formamidines: a facile and versatile procedure.

A focused library of formamidines having several diversity points has been prepared. The use of isocyanate resin as scavenger may offer several practical advantages over conventional procedures, such as the ease of workup and availability. The technique described herein was performed in a parallel synthesis format. The whole protocol has potential use in high throughput synthesis for the preparation and purification of libraries of unsymmetrical formamidines containing sets of different aliphatic substituents.

Synthesis of substituted benzofurans via microwave-enhanced catch and release strategy.

A microwave-enhanced procedure for the synthesis of substituted benzofurans starting from 2-(1-hydroxyalkyl)-phenols and using triphenylphosphine polystirene resin is reported. The benzofurans are isolated in good to high yields and purities by simple workup. The procedure can be applied to chiral alpha-alkyl-2-benzofuranmethanamines too.

An easy microwave-assisted synthesis of sulfonamides directly from sulfonic acids.

An easy and handy synthesis of sulfonamides directly from sulfonic acids or its sodium salts is reported. The reaction is performed under microwave irradiation, has shown a good functional group tolerance, and is high yielding.

A facile approach to the synthesis of chiral 2-substituted benzofurans.

An effective route to chiral optically active 2-substituted benzofurans directly from carboxylic acids is reported. This procedure, which allows the preparation of alpha-alkyl-2-benzofuranmethanamines from N-protected alpha-amino acids without sensible racemization phenomena, proceeds in good yields under mild conditions with the help of microwave irradiation.

Angeli-Rimini's reaction on solid support: a new approach to hydroxamic acids.

Angeli-Rimini's reaction has been performed for the first time on solid phase. A convenient one-step procedure for the synthesis of hydroxamic acids starting from aldehydes and solid-supported N-hydroxybenzenesulfonamide is reported. The hydroxamates are isolated in good to high yields and purities by simple evaporation of the volatile solvents, after treatment of the crude reaction mixture with sequestering agents.

Synthesis of 1-alkyl-4-imidazolecarboxylates: a catch and release strategy.

The novel alkyl N-methyl-N-polystyreneamino-2-isocyanoacrylate was used for the synthesis of 1-substituted imidazole-4-carboxylates utilizing a "catch and release" methodology. The reactions were performed under microwave irradiation, affording the title compounds in both high yields and chemical purity directly to solution, from the solid phase support.

Peptide nucleic acids (PNAs), a chemical overview.

Peptide nucleic acid (PNA) is a nucleic acid analogue and a fully synthetic DNA/RNA-recognising ligand with a neutral peptide-like backbone. In spite of the large change on the backbone structure, PNA molecules bind strongly to complementary DNA and RNA sequences. Originally conceived as ligand for the recognition of double stranded DNA, the unique physico-chemical properties of PNAs have led to the development of a variety of research and diagnostic assays. The extraordinary properties of PNA may advance routine clinical tests and environmental analyses that will utilise the PNA technology. PNAs may also have an impact on in situ hybridisation, cytogenetics and industrial microbiology. This paper presents some recent achievements on peptide nucleic acids and discusses, from the viewpoint of literature, what the potential is and what the limitations of such compounds are. This review, which is not intended to be exhaustive, is mostly aimed at the current progress in PNA chemistry, structure, and hybridisation, highlighting some applications too.

Microwave-assisted synthesis of isonitriles: a general simple methodology.

[reaction: see text] A facile conversion of formamides to isonitriles under very mild conditions and microwave irradiation is described. This simple and efficient method has been applied for the synthesis of both aliphatic and aromatic isonitriles in high yields.

New cellulose-supported reagent: a sustainable approach to guanidines.

[reaction: see text] A new cellulose-supported reagent for the synthesis of guanidine in aqueous medium is reported starting from commercially available functionalized cellulose beads. Primary and secondary amines, anilines, and amino acids were transformed to the corresponding guanidines in high yields and under very mild conditions.

A "catch and release" strategy for the parallel synthesis of 2,4,5-trisubstituted pyrimidines.

A resin capture and release strategy for making a combinatorial array of 2,4,5-trisubstituted pyrimidines is demonstrated by capturing beta-ketoesters and beta-ketoamides on a solid-supported piperazine. Through a cyclocondensation reaction, the solid-supported enaminone is reacted with several guanidines under heating or microwave irradiation affording the corresponding pyrimidines in good yield and chemical purity directly on solution. After this final step, the support can be effectively recycled.

Cellulose beads: a new versatile solid support for microwave- assisted synthesis. Preparation of pyrazole and isoxazole libraries.

The synthesis of libraries of substituted pyrazoles and isoxazoles has been developed via in situ generation of polymer-bound enaminones. The synthetic protocol makes use of commercially available aniline cellulose, a low-cost and versatile biopolymer, under very mild conditions. This new support allowed us to carry out reactions in polar solvents under both conventional heating and MW irradiation without degradation of the polymer. The reaction between cellulose-bound enaminone and hydroxylamine or hydrazines to afford the target heterocycles in high yields directly in solution is the key step. The support can be conveniently recycled.

Simple one-flask method for the preparation of hydroxamic acids.

[reaction: see text] A one-step conversion of carboxylic acids to hydroxamic acids under very mild conditions is described. This simple and efficient method has been applied for the synthesis of enantiopure hydroxamate of alpha-amino acids and peptides.

Trichloroisocyanuric/TEMPO oxidation of alcohols under mild conditions: a close investigation.

Efficient oxidation of primary alcohols to the corresponding carboxylic acids can be carried out at room temperature and in acetone/water, using trichloroisocyanuric acid (TCCA) in the presence of catalytic TEMPO. The mild conditions of this procedure and the total absence of any transition metal make this reaction suitable for safe laboratory use. A possible mechanism is presented and discussed.

Beckmann rearrangement of oximes under very mild conditions.

A variety of ketoximes, easily prepared from the corresponding ketones, undergo the Beckmann rearrangement upon treatment with 2,4,6-trichloro[1,3,5]triazine in N,N-dimethylformamide at room temperature in excellent yields. This procedure can be applied to aldoximes for obtaining the corresponding nitriles.

Mild and highly selective formyl protection of primary hydroxyl groups.

Efficient conversion of primary alcohols to the corresponding formate esters can be carried out at room temperature in methylene chloride, using 2,4,6-trichloro-1,3,5-triazine and N,N-dimethylformamide in the presence of lithium fluoride. This procedure appears as a valid method for selectively protecting primary hydroxyl groups.

An efficient route to alkyl chlorides from alcohols using the complex TCT/DMF.

[reaction: see text] Efficient conversion of alcohols and beta-amino alcohols to the corresponding chlorides (and bromides) can be carried out at room temperature in methylene chloride, using 2,4,6-trichloro[1,3,5]triazine and N,N-dimethyl formamide. This procedure can also be applied to optically active carbinols.