Oxocarbenium ion cyclisations under non-acidic conditions: Synthesis of tetrahydropyran analogues of the pseudomonic acids

Allylated Monosaccharides as Precursors in Triple Reductive Amination Strategies: Synthesis of Castanospermine and Swainsonine

“…The configuration of the new carbinol center was tentatively assigned by comparison of 1 H NMR of both epimers with those of related chain extended gluco derivatives: ref b.…”

“…Studies from this laboratory have shown that C6-allylated monosaccharides (e.g., 5 ) on treatment with halonium ion undergo a facile, high-yielding reaction to the halo-THF aldehyde 6 (Scheme ) . When the reaction is performed under anhydrous conditions, in the presence of an alcohol, the acetal 7 is obtained.…”

Total Diastereofacial Selective Iodofunctionalization of Terpene Derivatives Based on Ipy2BF4

“…The formation of 3 could be easily explained by considering the iodocarbocyclization reaction in which the phenyl group in the quaternary center of 1h acts as a nucleophile, in a process that is favored by the ideal location of the partners due to the terpene conformation. 7e, In the same way, compound 1i could undergo an iodooxycyclization reaction with concomitant debenzylation reaction leading to iodo derivative 4 . The absolute configuration of products 3 and 4 clearly indicate again that the reactions of 1h and 1i proceed in the same diastereofacially selective manner, that is, the iodonium ion attacking the face of the olefin where the allylic oxygen of the acetonide is placed.…”

Electron Transfer Initiated Heterogenerative Cascade Cyclizations: Polyether Synthesis under Nonacidic Conditions

“…The need for strong Lewis or protic acids in the initiation steps of these reactions, however, can prohibit the inclusion of acid-sensitive functional groups into cyclization substrates and products. This limitation can be circumvented by initiating these processes with a heterogenerative reaction 4 in which a reactive intermediate is formed under nonacidic conditions and subsequently disproportionates into a potent electrophile …”