Search

The parallel synthesis of a library of toxoflavin derivatives is described. The microwave-assisted approach involves the de novo generation of the heterocyclic scaffold and allows for facile introduction of a variety of fragments.

The monodentate ligand 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phospha-adamantane (PA-Ph) is shown to be highly effective in palladium-catalyzed carbonylative cross-coupling. Aryl and vinyl halides were efficiently converted to carboxylic acids, amides and to primary, secondary, and tertiary esters, respectively. Application of the Pd(OAc)2/PA-Ph (1:1) catalyst system proved critical in the methoxycarbonylation of a functionalized nitroresorcinol halide, allowing convenient access to novel platensimycin sulfonamide analogs.

Substituted imidazoles can be prepared efficiently from cyclic or acyclic 1,2-aminoalcohols via a four-step procedure involving acylation of the amine, oxidation of the alcohol, imine formation and cyclization. Examples are presented and the methodology is applied in the generation of a library of compounds containing a fused imidazole-azepine motif.

The parallel synthesis of a library N1- and C3-substituted-pyrazolo[3,4-d]pyrimidines is described. The microwave-assisted approach involves the de novo generation of the heterocyclic scaffold, facile alkylation at N1 via either a Mitsunobu or a direct alkylation reaction and arylation at C3 via a Suzuki reaction.

The radical addition of PH3 to limonene results in the formation of 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonane, which has been characterized by X-ray crystallographic analyses of its oxidation products, 2-(4-methylcyclohexyl)propylphosphonic acid and 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonan-2-ol-oxide.

Treatment of 1-diazo-3-(2-thienyl)-2-propanone with catalytic rhodium (II) acetate results in cyclopropanation followed by acid-catalyzed ring opening and tautomerization to yield 5,6-dihydro-4H-cyclopenta[b]thiopen-5-one. Under the same conditions, however, the isomeric 1-diazo-3-(3-thienyl)-2-propanone generates a cyclopropane intermediate which undergoes [4+2] cycloreversion, isomerization and Diels-Alder dimerization to give a complex spiro-disulphide. While the 2-substituted thiophene behaves like other homologous members of the thienyl series, the isomeric 3-substituted thiophene undergoes chemistry seen previously with analogous furanyl compounds. The insight into the mechanistic underpinnings provided by preliminary molecular modeling at a PM3 level is discussed.

The use of Pd 2 dba 3 ·CHCl 3 and 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phospha-adamantane has been shown to facilitate the effective amination of aryl halides with aromatic or aliphatic amines in high yields.

The use of a catalyst system based on Pd 2 dba 3 ·CHCl 3 and 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phospha-adamantane allows for Suzuki coupling aryl halides with an array of boronic acids on a solid-phase platform. The reactions can be carried out at room temperature with low palladium loadings in high yields.

The poly-methylene interrupted fatty acid 5(Z),11(Z)-eicosadienoic acid and its tetradeuterated analogue were prepared via a convergent synthetic sequence.