Letters in Organic Chemistry - Volume 3, Issue 2, 2006

In this report, recently developed multi-component coupling reactions proceeding via symmetrical and unsymmetrical bis-π-allylpalladium complexes are reviewed. The transformations provided an efficient access to 1,7-octadienes, oxa- and aza-heterocycles, medium-size carbocycles, homoallylic alcohols and α,β- unsaturated-δ-lactones.

During the last decade, peroxidation of polyunsaturated fatty acids and corresponding esters has attracted increased research attention, mostly due to its involvement in the origin and development of many chronic diseases. This short report focuses on the state-of-the-art of the mechanistic interpretation of lipid autoxidation and the design of antioxidants of new generation.

In this paper we report some theoretical and experimental evidence concerning the nature of the allyl-In intermediate generated by umpolung of allyl-Pd complexes in the Pd(OAc)2/TPPTS catalysed allylation reaction of benzaldehyde. The allylic substrate reacts at the substituted terminus, because of the formation of an equilibrating mixture of η1-allyl-In(I) specie with the γ-substituted regioisomer being more reactive.

The total synthesis of a 2,3-disubstituted benzofuran, designed as a structural analogue of a bioactive arachidonic acid metabolite, the 8-(S)-HETE, is reported. This heterocyclic derivative has been evaluated as dual agonist of the PPARα and PPARγ nuclear receptors.

Employing water as medium for aerobic oxidation and dynamic kinetic resolution of activated alcohols with RuCl3, n H2O resulted in simple and recyclable catalytic systems.

The electrochemical oxidation of Hantzsch 1, 4-dihydropyridins (1, 4-DHPs) in the mixture of ethanol-water on carbon electrode is described. Various Hantzsch 1, 4-dihydropyridines were oxidized electrochemically to obtain the corresponding saturated pyridines in high yields.

Upon UV-irradiation in chloroform solution, some of the 2,4,4,6-tetrasubstituted-4H-thiopyran-1-oxides underwent deoxygenation to give the corresponding 4H-thiopyrans in good yields together with the corresponding 4Hthiopyran- 1,1-dioxides as minor components. Moreover, in benzene as an aromatic solvent oxenoid functionalization was observed.

A novel aerobic, environmentally friendly oxidation of hydroxylamines to nitrones catalyzed by tetra-n-propylammonium perruthenate (TPAP) is reported. Complete conversions and reasonable to excellent yields were obtained for cyclic hydroxylamines.

Montmorillonite K10-supported manganese(II) chloride was found to be an efficient and convenient catalyst for the oxidative cleavage of oximes, phenylhydrazones and semicarbazones to the corresponding carbonyl compounds with molecular oxygen.

Various diesters successfully undergo a double Fries rearrangement to afford the corresponding bis o-hydroxylaryl ketones, in the presence of AlCl3 under microwave irradiation.

Ring-opening-cross-metathesis (ROCM) reaction has been used to prepare spiro-indane derivatives containing six rings. The Diels-Alder (DA) chemistry of indan-2-spiro(cyclopenta-2,4-diene) 1 with various dienophiles such as 1,4-benzoquinone and its derivatives gave the corresponding DA products in moderate to good yields. Also, we report an improved procedure for preparation of the spiro-diene 1 using phase-transfe Read More

3,5-Diarylisoxazoles and 1,3,5-triarylpyrazolines are synthesized via Michael addition of "hydroxylamine hydrochloride, phenylhydrazine" respectively over chalcones followed by cyclization using K2CO3 as solid support. Reactions are shown to be highly regioselective regardless of the nature of the substituent in the substrates and afforded single isoxazole and pyrazoline isomer in excellent yields.

A highly efficient stereoselective total synthesis of piperidine alkaloid (+)-sedamine has been described utilizing two regioselective ring opening reactions of epoxide with vinyl metallic reagent and a ring closing metathesis reaction as the key steps.

Several simple amino acids derived chiral sulfonamide ligands were synthesized in simple three steps. When we used these ligands in the asymmetric addition of phenylacetylene to aldehydes, the corresponding propargylic alcohols were isolated with good yields. The highest ee value was obtained up to 99%. The results proved that the backbone of the chiral source greatly influenced the enantioselectivity.

An eco-friendly facile synthesis of imidazo[2,1-b]-1,3,4-thiadiazoles is described using ionic liquid, [bmim]PF6 (1-butyl-3-methylimidazolium hexafluorophosphate). The use of recyclable catalyst demonstrates the advantages of significant rate enhancement along with improved yields. The protocol is green and effective for producing the desired target moiety.

A mixture of ethyl acetoacetate and various aldehydes in the presence of ammonium salts was converted to Hantzsch ethyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylates under mild and green conditions with good to excellent yields.

KF/Al2O3 efficiently catalyzes aza-Michael addition of indole and 3-methylindole to a variety of electron-deficient conjugated alkenes such as α,β-unsaturated ketones, amides and nitriles. The N-alkylation adducts are produced in good to excellent yields and relatively in short times. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency.

A simple, rapid, atom economy and highly efficient green protocol has been developed for the reactions of indole with carbonyl compounds under solvent- free conditions. The attractive features of these procedures are the mild reaction conditions, high conversions, cleaner reaction profiles, inexpensive and environmentally friendly lithium perchlorate and short reaction times.

Regioselective halogen/lithium permutation reactions were carried out on polybrominated biaryls. Thus, highly functionalized, dissymetrically substituted biaryls become easily accessible on gram scale.