Chemoselective and Diastereoselective Intramolecular (3+2) Cycloadditions of Epoxy and Aziridinyl Enolsilanes.

Epoxy and aziridinyl enolsilanes react as oxyallylic cation equivalents in highly chemo- and diastereoselective intramolecular (3+2) cycloadditions with a range of dienes and olefins. With acyclic dienes, the (3+2) cycloaddition outcompetes the (4+3) pathway traditionally observed in this kind of system almost exclusively. With both conjugated dienes and isolated olefins, excellent diastereoselectivities are observed, and cycloadducts can be obtained in optically-enriched forms.

Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds.

The photo-induced cleavage of C(sp)-Cl bonds is an appealing synthetic tool in organic synthesis, but usually requires the use of high UV light, photocatalysts and/or photosensitizers. Herein is described a direct photo-induced chloroarene activation with UVA/blue LEDs that can be used in the reductive Heck cyclization of indoles and without the use of a photocatalyst or photosensitizer. The indole compounds examined display room-temperature phosphorescence.

Versatile Glycosyl Sulfonates in β-Selective C-Glycosylation.

C-Glycosides are both a common motif in many bioactive natural products and important glycoside mimetics. We demonstrate that activating a hemiacetal with a sulfonyl chloride, followed by treating the resultant glycosyl sulfonate with an enolate results in the stereospecific construction of β-linked C-glycosides. This reaction tolerates a range of acceptors and donors, including disaccharides.

Recent Developments in Stereoselective Chemical Glycosylation.

Because of their pivotal biological functions, attention to sugars and glycobiology has grown rapidly in recent decades, leading to increased demand for homogeneous oligosaccharides. The stereoselective preparation of oligosaccharides by chemical means remains challenging and continues to be a vivid research area for organic chemists. In the past decade, new approaches and reinvestigated traditional methods have transformed the field.

Dearomative Intramolecular (4+3) Cycloadditions of Arenes with Epoxy and Aziridinyl Enolsilanes.

An intramolecular (4+3) cycloaddition of epoxy and aziridinyl enolsilanes with benzene, naphthalene, and anthracene derivatives is reported. Highly functionalized polycyclic alcohols and amines are generated under relatively mild reaction conditions with yields up to 89 %. Optically enriched cycloadducts are obtained from cycloadditions of enantiomerically pure epoxides and aziridines.