Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reactionbetween hydantoins or thiohydantoins and dialkyl acetylenedicarboxylates in the presence oftriphenylphosphine. These phosphoranes undergo smooth intramolecular Wittig reaction followedby an electrocyclic ring opening to produce dialkyl (E)-2-(2,5-dihydro-5,5-diaryl-2-thioxo-1H-imidazol-4-yl)fum...

An intramolecular Prins macrocyclization reaction was successfully employed in the synthesis of polycavernoside A.

[reaction: see text]. The copper acetate mediated intramolecular O-arylation of phenols with phenylboronic acid pseudopeptides is the key step in the preparation of macrocyclic biphenyl ether hydroxamic acid inhibitors of collagenase 1 and gelatinases A and B. The intramolecular macrocyclization was found to be mild and tolerant of common chemical functionality. This methodology should provide ...

With the mediation of phosphine, the direct intramolecular coupling of two electrophiles - alkyl halides with electron-deficient olefins - has been successfully realized in an intramolecular conjugate addition manner. The reaction provides a new approach for the synthesis of chromans and relevant analogues.

The rhodium-catalyzed intramolecular direct arylation of imidazole and benzimidazole derivatives via double C-H bond activation is described. This approach provides new access to a wide range of imidazo and benzimidazo[2,1-a]isoquinoline derivatives in moderate to high yields. This reaction provides an alternative method to the known Pd-catalyzed intramolecular oxidative cross-coupling reactions.

The spontaneous and pepsin-catalyzed activation of pepsinogen has been observed and analyzed kinetically. At appropriate protein concentrations (1 mg per ml or less), a kinetically first order reaction was observed in the pH range 1 to 3, implying an intramolecular activation mechanism. Substantiation of the first order reaction came from a linear plot of log pepsinogen concentration versus tim...

Intramolecular cyclization of nitrogen-tethered alkynyl esters catalyzed by phosphazene organosuperbases P2-tBu and P4-tBu was investigated. Both acyclic and cyclic substrates underwent 5-exo-dig and 5-endo-dig cyclization. This reaction is a rare example of the intramolecular addition of enolates of simple esters to alkynes.

During continuing studies with a novel oxidative gold oxyarylation reaction, arylsilanes were found to be competent coupling partners, providing further evidence for an intramolecular electrophilic aromatic substitution mechanism. While providing yields complementary to those of the previously described boronic acid methods, the use of trimethylsilanes reduces the observation of homocoupling by...

Standard reaction conditions for the desilylation of acetylated furanoside (riboside, arabinoside and xyloside) derivatives facilitate acyl migration. Conditions which favour intramolecular and intermolecular mechanisms have been identified with intermolecular transesterifications taking place under mild basic conditions when intramolecular orthoester formations are disfavoured. In acetyl ribos...

A concise synthetic strategy has been developed for the synthesis of the macrolactone core 2 of a unique polyketide callyspongiolide 1. The key features of the strategy included an Evan's asymmetric alkylation, diastereoselective Michael type alkylation, Brown's asymmetric allylation reaction, an allylic alkylation of an activated Z-allylic alcohol and an intramolecular Z-selective intramolecul...