Introduction of Bicyclic Ketal Chemistry: Synthesis and Transformation Reaction of 6,8-Dioxabicyclo[3.2.1]octane Skeletal System

Abstract

A stereo-and regioselective bicyclic ketal synthesis and several facile one-pot transformations of bicyclic ketals are described with plausible mechanisms. Products have included d,e-unsaturated ketones, mono-and diacetoxy ketones, transketalized ketones, cis-and trans-cyclic ethers, 1,5-diketones, cis-1,2-cyclopentanediols, 2,6-disubstituted pyridines, 2,3,6-trisubstituted pyridines, and conjugated and nonconjugated cyclohexenones. 4Conclusion

Gold-Catalyzed Cascade Annulations of 2-(Ynol)aryl Aldehydes: Facile Synthesis of Benzochromanes and Benzobicyclo[n.3.1]acetals

“…Giving gold’s notable affinity toward alkynes and our continuous interest on gold chemistry, we investigated the gold-catalyzed trasformations of 2-alkynylaryl aldehydes bearing a nucleophile in the molecule. Herein, we wish to report the facile synthesis of benzochromanes and benzobicyclo[ n .3.1]acetals via a gold-catalyzed cascade annulation of 2-(ynol)aryl aldehydes or ketones.…”

Asymmetric Total Synthesis of (+)-Didemniserinolipid B via Achmatowicz Rearrangement/Bicycloketalization

“…Our interest in didemniserinolipids was triggered by the central 6,8-DOBCO framework, which was prepared conventionally by intramolecular dehydrative ketalization of a keto diol . We envisioned that such bicyclic ketal core (isolevoglucosenone) could be readily synthesized by oxidative rearrangement (Achmatowicz rearrangement) of furfuryl diol followed by dehydrative ketalization (Scheme ), a process originally developed by Ogasawara for diastereoselective synthesis of saccharides.…”

Scalable Asymmetric Total Syntheses of (+)-Psoracorylifol B and (+)-ent-Psoracorylifol C

“…Nonetheless, in continuation of our interest in the synthetic utilities of Achmatowicz rearrangement, we envisioned that the 6,8-DOBCO core structure ( 6 ) could be constructed by sequential Achmatowicz rearrangement/bicycloketalization (AR/BCK, 8 → 6 ), a protocol originally developed by Ogasawara for the enantio- and diastereoselective synthesis of hexoses from furfural. To our surprise, this AR/BCK strategy has been rarely exploited in the synthesis of 6,8-DOBCO, which instead was prepared conventionally by dehydrative ketalization of the corresponding dihydroxyl ketone . Given that the structure of type 8 could be synthesized straightforwardly through Julia–Kocienski olefination and Sharpless asymmetric dihydroxylation, we first explored this strategy for the synthesis of the 6,8-DOBCO framework of PsB and ent -PsC.…”