Letters in Organic Chemistry - Volume 7, Issue 1, 2010

A convenient protocol for the synthesis of biaryls from arenediazonium salts and potassium aryltrifluoroborates in refluxing methanol catalyzed by Pd/C is described. The protocol is simple to execute and gives moderate to high yields of cross-coupling products in most cases.

The nitrile group is shown to direct the palladium-catalysed hydroarylation of internal alkynes bearing a pendant nitrile with boronic acids.

Moderate to good yields of symmetrical biaryls were obtained under environmental friendly conditions via homocoupling reaction of aryl boronic acids catalyzed by Pd(OAc)2 / K2CO3 in water. Our method explores the synthetic utility of the homocoupling reaction of aryl boronic acids which may provide a simple and general alternative to the Suzuki reaction to achieve symmetrical biaryls.

Three novel C2-symmetrical chiral primary amines were synthesized from chiral BINOL and diamines. Then their catalytic activities in the asymmetric aldol reactions were evaluated, and the result indicated that 1c was the optimal organocatalyst. The reaction of a variety of aromatic aldehydes with aliphatic ketones, catalyzed by 20 mol % 1c in the addition of benzoic acid in carbon tetrachloride, afforded the aldol pro Read More

Polymer-anchored (Merrifield, trityl chloride, Wang p-nitrophenyl carbonate and triazene supports) nortropinone, or N-protected nortropinone derivatives in solution, were subjected to deprotonation with LDA or chiral lithium amides, and the resulting lithium enolates were trapped with an aldehyde. The aldols were obtained with moderate to good yields (44-84%) and enantioselectivities (44-86% ee).

This is a new example of a nonmetallic small-molecule catalyst for direct intermolecular aldol reactions. We found L-lysine is an effective catalyst for this condensation between unmodified acetone and a variety of aldehydes in the presence of pure water. This green catalyst system could be reused.

Reaction between aryl 1,3-diketoesters 2a-e and hydroxylamine hydrochloride has been investigated under different experimental conditions. Whereas acid conditions gave principally 3,5-isoxazole esters (3a-e), reactions under neutral and basic conditions led to different 4,5 and 2,3-dihydro-hydroxy-isoxazoles 4a-e and 5a-e.

Ionic liquid 1,3-dimethylimidazolium methanesulfonate was used to prepare α-amino acids benzylic esters from unprotected amino acids and benzyl chloride. Esterification of several amino acids was achieved with satisfactory yields: by-products can be removed by a simple work-up procedure to afford the pure product. The described method is simple, mild, rapid and save.

A novel and practical asymmetric synthesis of (S)-N-[[3-(3-fluoro-4-morpholinyl phenyl)-2-oxo-5-oxazolidinyl] methyl]acetamide has been developed by a new approach without recourse to chromatography and it is employed for the synthesis of Linezolid. This involves the reaction of (R)-epichlorohydrin with N-arylcarbamates and subsequent regioselective epoxide ring opening of resulted intermediate by sodium azide.

A new simple synthesis of tubacin is reported. It entails the formation of the syn-1,3-diol unit and its stereoselective ketalization with a functionalized benzaldehyde derivative.

The palladium-catalysed aminocarbonylation of 2-iodobornene and 3-iodo-2-quinuclidene, possessing iodo alkene functionality, resulted in the high-yielding synthesis of the corresponding carboxamide derivatives. The substrates were synthesised from camphor and 3-quinuclidone, respectively, via their hydrazones. The chemoselective homogeneous carbonylation reaction of synthetic value was carried out under mild reaction c Read More

In the presence of a catalytic amount of InCl3·4H2O, trioxane was first used as the methylating agent for multimethylated aromatic compounds such as pentamethylbenzene, 1,2,4,5-tetramethylbenzene and 1,3,5-trimethylbenzene to afford hexamethylbenzene in fair to high yields.

An economic, efficient access to 4H-chromene derivatives was found. In the presence of threo-(1S,2S)-2- amino-1-(4-nitrophenyl)-1,3-propanediol, a chiral “waste” in the production of chloromycetin, and one-pot threecomponent Hantzsch reaction of dimedone, aldehydes and malononitrile at room temperature furnished 4H-pyran derivatives in good to excellent yield.

An efficient diastereoselective synthes.is of γ-phthalimido-β-hydroxy esters and N-protected 4-amino-1,3- diols, starting from natural amino acids is described. The key synthetic strategies involve diastereoselective reduction of γ-phthalimido-β-keto esters with NaBH4 as hydride reducing. The diastereoselective reduction has been found to be highly selective if carried out in methanol at -78°C. Furthermore, the resulting diaster Read More

Natural α-amino acids-derived ionic liquids comprising 1-butyl-3-methylimidazolium cation and amino acid anion, i.e. [bmim][AA] were found to be effective catalysts for the coupling of various epoxides and CO2 to produce cyclic carbonates in good yields and selectivity, which requires no additional organic solvent and avoids halogen.

A series of 7-heteroaryl-4-oxo-4,7-dihydrothieno[2,3-b]-pyridine-5-carboxylic acids (8a-d) and their methyl esters (7a-d) were prepared by cyclization of the respective 2-(2,5-dichlorothien-3-yl)-3-(N-heteroarylamino)acrylates (6a-d). The latter are accessible from methyl 2-(2,5-dichlorothien-3-yl)-3-ethoxyacrylate (5) which is obtained via methyl 3-(2,5-dichlorothien-3-yl)-3-oxopropanoate(4). Of the present series Read More

With 2-octyl dithieno[2,3-b:3',2'-d]thiophene as raw material, three steps including formylation, McMurry reaction and photocylization were employed to generate dioctyl-hexathia[7]heterohelicene in total yield of 29.9'. The crystal analysis shows that some short intermolecular interactions including S...S and C...S interactions were observed in the crystal of target compound.

The first direct lithiation of the pyridine ring of benzo[h]- and benzo[f]- quinolines is reported. The method allowed the introduction of different electrophiles (Cl, Br and SPh) in 2-position. Other groups were introduced by direct nucleophilic addition of alkyllithiums allowing further transformations to functional groups such as esters and thiolesters.