Tetraarylphosphonium salts as soluble supports for oxidative catalysts and reagents.

Tetraarylphosphonium (TAP)-supported DMSO, TEMPO, and DIB reagents were synthesized and used for the oxidation of alcohols, including Swern oxidation and for the alpha-acetoxylation of ketones. By taking advantage of the predictable solubility properties of the TAP unit, simple precipitation and filtration of the phosphonium moiety permit complete separation of the desired oxidation products. This paper describes the preparation of these three TAP-supported oxidative reagents and their activity in the aforementioned oxidative transformations.

Tetraarylphosphonium-supported carbodiimide reagents: synthesis, structure optimization and applications.

New tetraarylphosphonium (TAP)-supported alkyl- and arylcarbodiimides were synthesized and used as coupling reagents for esterification reactions, amidation reactions and dehydration reactions of hydroxyesters. Taking advantage of the solubility properties imparted by the tetraarylphosphonium unit, a simple precipitation and filtration allowed complete separation of the urea by-products. This paper describes the structure optimization study of the various TAP-supported carbodiimide reagents to obtain the desired reactivity and solubility profile.

Removal, recovery, and recycling of triarylphosphonium-supported tin reagents for various organic transformations.

Phosphonium-supported tin reagents and catalysts were prepared and were shown to be effective in Stille couplings, radical dehalogenations, radical cyclizations, and carbonyl allylations. Not only could the tin residues be removed from the crude reaction mixture through a phase separation process but also they could be recovered and recycled.

Enantioselective synthesis of the C1-C11 fragment of bafilomycin A1 using non-Wittig and desymmetrization strategies.

The synthesis of the C1-C11 fragment 33 of bafilomycin A(1) was achieved. Intermediate ketone 16 was prepared in six steps from 4-oxopimelate 13. Desymmetrization of this ketone using Koga's chiral base followed by TMSCl quench furnished silyl enol ether 17 with excellent enantioselectivity.

Hydroxy-directed diastereoselective installation of a methyl group on indalone models and spiroketal potential precursors for the bafilomycin A(1) C15-C25 subunit.

Current efforts devoted to the synthesis of Bafilomycin A(1) led us to investigate a synthetic route through a spiroketal intermediate for the construction of the C15-C25 subunit. Preliminary studies for the diastereoselective installation of the methyl-16 cis with respect to the vicinal OH-15 group through radical opening of either siloxafuran intermediate 7 or cyclopropyl compounds 9 and 13 have been carried out using model compounds derived from commercial Indalone 6. In each case the expected "cis" diastereoisomer was obtained in good to excellent yield.