Letters in Organic Chemistry - Volume 4, Issue 5, 2007

5-Hydroxymethyl-furan-2-nitrileoxide undergoes [3+2] cycloadditions with alkenes to give 3-(2-furanyl)-4,5- dihydo-isoxazole ring system in 71-84% yield. Cycloaddition with one equivalent of dimethylacetylene dicarboxylate gave a 1:1 adduct with 3-(2-furanyl)-isoxazole ring system and further reaction with a second equivalent in a [4+2] Diels- Alder reaction yielded a 3-(7-oxa-bicyclo[2.2.1]hepta-2,5-dien-1-yl)-isoxazole. Hydrogenolysis of 3-(2-furanyl)-4,5- dihydo-isoxazole adducts with Raney-Ni catalyst resulted the ring opening of the 4,5-dihydro-isoxazole ring.

Synthesis of oxepin-annulated quinolone heterocycles by the combination of Claisen rearrangement, the ringclosing metathesis and Diels-Alder reaction is described. The RCM or RCEM proceeded smoothly in the presence of Grubbs' first generation catalyst at room temperature under nitrogen atmosphere.

The study of Friedel-Crafts acetylation of phenanthrene with acetic acid in polyphosphoric acid, along with rearrangements and deacetylations of acetylphenanthrene isomers, indicated its reversibility. The structures of (E)-2- AcPHN and (Z)-9-AcPHN were determined by X-ray crystallography. PM3 calculations predicted that 9-AcPHN is the kinetically controlled while 2-AcPHN and 3-AcPHN are the thermodynamically controlled products, in accordance with experiment. The mutual rearrangements of 2-AcPHN and 9-AcPHN are noted.

An expeditious route to nitriles via dehydration of primary amides using halotriphenoxy phosphonium halides (TPPX2, X = Cl or Br) is described. The reaction proceeds under very mild conditions and allows the preparation of aromatic and aliphatic nitriles in good to excellent yields.

A new synthesis of twelve-, fifteen-, and eighteen-membered benzoazacrown ethers using palladium-catalyzed intramolecular amination is reported. Couplings proceeded in good yields using an in situ generated Pd(0) catalyst associated to N,N'-bis(2,6-diisopropylphenyl)dihydroimidazol-2-ylidene (SIPr) as ligand and t-BuONa as the base.

A microwave enhanced ligand- and base-free protocol for the cross-coupling of arenediazonium tetrafluoroborates with potassium aryltrifluoroborates has been developed.

The formation of acrylamide from asparagine and β-alanine containing peptides without the involvement of an additional carbonyl compound is described.

The eco-friendly synthesis and preliminary biological evaluation of new dialkyl 2- and 3-quinoline-substituted α-aminophosphonates have been described. The conventional and microwave-assisted one- and two-steps reactions of the appropriate aromatic aldehyde, amine and dialkyl phosphite, carried out without or in the presence of solvent and catalyst, have been compared and discussed.

We report the binding properties of ammonium glycolic and pyridinium amido calix[4]arenes towards alkali cations. UV spectrophotometry titrations have been carried out in methanol and acetonitrile. In one case the presence of the anions improves the complexation compared to the neutral homologues.

Reactions of 3-(polyfluoroacyl)chromones with indole and N-methylindole in refluxing pyridine and Nmethylpyrrole under solvent-free conditions proceed at the C(2) atom of the chromone system with pyrone ring opening and subsequent cyclization to 2-hydroxy-3-(indol-3-ylmethylene- or pyrrol-2-ylmethylene)-2-(polyfluoroalkyl)chroman- 4-ones in good yields. Treatment of these compounds with morpholine gives trans-indolyl(pyrrolyl)chalcones.

Simple and efficient cyclopalladated ferrocenylimine/Cu and cyclopalladated ferrocenylimine catalyzed cyanation of aryl bromides with K4[Fe(CN)6] 3H2O were described. These procedures are applicable to both activated and deactivated aryl bromides. The corresponding benzonitriles were formed in good to excellent yields.

A highly efficient and environmentally benign reaction of dimedone with various aldehydes and Narylthioureas to afford monastrol analogues is revealed. The reaction is found to be sensitive towards the steric and electronic effects of the substituents in variable components. A quantitative optimization of catalytic support is also presented.

A series of spirobenzopyran derivatives 9a-9c bearing a dithiocarbamate/dithiocarbonate as the metal-ligating group were designed for colormetric metal sensors and synthesized. The binding properties of the sensors with different metal ions were investigated. In terms of response time, selectivity and sensitivity, sensor 9a showed a good sensing ability toward mercury ion.

A series of 7-carbamate derivatives of quercetin were synthesized. Using dichlorodiphenylmethane and benzyl bromide to partly protect the hydroxyl groups, the protected quercetin then reacted with amino acid ester isocyanates, deprotection the hydroxyls with hydrogen using a palladium on carbon catalyst, then treating with ammonia gas to give the ammonium salts of 7-carbamate derivatives of quercetin.

An efficient and convenient method for thiazolo[3,2-a]pyrimidines from cyclization reaction of dihydropyrimidine- thiones with α-bromoacetone in aqueous media is described.

An efficient single pot route is presented involving the use of O,N-perhydro 1,3-heterocycles as carbonyl equivalents for the synthesis of 5,5-disubstituteddipyrromethanes and meso-tetraarylporphyrins through a high yielding modified Adler route.

Regioselective synthesis of spiro [indole -3(3H), 2' (3H)perimidine]2'(1H)one (4a-e) for potential application in cancer treatment \ under conventionally and microwave irradiation using different solvents/solid support has been studied. A judicious choice of the reaction conditions allowed the titled product 4a-e to be generated in excellent yields.