Main observation and conclusion
Herein, we report an efficient, tunable system for electrochemical reduction of ketones and phthalimides at room temperature without the need for stoichiometric external reductants. By utilizing NaN3 as the electrolyte and graphite felt as both the cathode and the anode, we were able to selectively reduce the carbonyl groups of the substrates to alcohols, pinacols, or methylene groups by judiciously choosing the solvent and an acidic additive. The reaction conditions were compatible with a diverse array of functional groups, and phthalimides could undergo one‐pot reductive cyclization to afford products with indolizidine scaffolds. Mechanistic studies showed that the reactions involved electron, proton, and hydrogen atom transfers. Importantly, an N3/HN3 cycle operated as a hydrogen atom shuttle, which was critical for reduction of the carbonyl groups to methylene groups.
C-vinyl glycosides are an important class of carbohydrates and pose a unique synthetic challenge. A new strategy has been developed for stereoselective synthesis of Cvinyl glycosides via Pd-catalyzed directed C À H glycosylation of alkenes with glycosyl chloride donors using an easily removable bidentate auxiliary. Both the g C À H bond of allylamines and the d CÀH bond of homoallyl amine substrates can be glycosylated in high efficiency and with excellent regioand stereoselectivity. The resulting C-vinyl glycosides can be further converted to a variety of C-alkyl glycosides with high stereospecificity. These reactions offer a broadly applicable method to streamline the synthesis of complex C-vinyl glycosides from easily accessible starting materials.Scheme 1. Structure and synthesis of C-vinyl glycosides.
The first total syntheses of three unusual norrisolidetype rearranged spongian diterpenes, cheloviolene C, seconorrisolide B, and seconorrisolide C, have been accomplished via a common intermediate through late-stage ring-scissoring. The synthesis features a Wolff ring contraction for the synthesis of the trans-hydrindane system, and a crucial retro Diels-Alder reaction/intramolecular ene cyclization for the rapid stereoselective construction of the furo[2,3-b]furan system, which is commonly seen in rearranged spongian diterpenes.
Leucosceptroids are sesterterpenoids with potent antifeedant and antifungal activities. An efficient stereoselective construction of the highly congested [5,6,5] tricyclic framework of leucosceptroid H is presented. This framework bearing eight contiguous stereogenic centers, including three tetrasubstituted ones, could serve as a common intermediate for the collective total synthesis of the leucosceptroid family of natural products. Letter pubs.acs.org/OrgLett
The first total syntheses of three unusual norrisolidetype rearranged spongian diterpenes, cheloviolene C, seconorrisolide B, and seconorrisolide C, have been accomplished via a common intermediate through late-stage ring-scissoring. The synthesis features a Wolff ring contraction for the synthesis of the trans-hydrindane system, and a crucial retro Diels-Alder reaction/intramolecular ene cyclization for the rapid stereoselective construction of the furo[2,3-b]furan system, which is commonly seen in rearranged spongian diterpenes.
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