Asymmetric Synthesis and Chiroptical Properties of Enantiopure Helical Ferrocenes.

An enantiopure helical ferrocene ( R)-5 with five ortho-condensed aromatic rings was synthesized using a PtCl-catalyzed cycloisomerization of planar-chiral 2-ethynyl-1-(4-phenanthrenyl)ferrocene ( R)-6f, prepared in 3 steps from known enantiopure sulfinyl ferrocenyl boronic acid ( S, S)-7, as the source of planar chirality. This pentacyclic helical ferrocene showed a very high optical rotation value and strong circular dichroism (CD) signals.

Generating carbyne equivalents with photoredox catalysis.

Carbon has the unique ability to bind four atoms and form stable tetravalent structures that are prevalent in nature. The lack of one or two valences leads to a set of species-carbocations, carbanions, radicals and carbenes-that is fundamental to our understanding of chemical reactivity. In contrast, the carbyne-a monovalent carbon with three non-bonded electrons-is a relatively unexplored reactive intermediate; the design of reactions involving a carbyne is limited by challenges associated with controlling its extreme reactivity and the lack of efficient sources.

A Stereoconvergent Cyclopropanation Reaction of Styrenes.

The first stereoconvergent cyclopropanation reaction by means of photoredox catalysis using diiodomethane as the methylene source is described. This transformation exhibits broad functional group tolerance and it is characterized by an excellent stereocontrol en route to trans-cyclopropanes regardless of whether E- or Z-styrene substrates were utilized.

Mild access to planar-chiral ortho-condensed aromatic ferrocenes via gold(i)-catalyzed cycloisomerization of ortho-alkynylaryl ferrocenes.

An efficient approach to (Rp) planar-chiral tri- and tetracyclic ortho-condensed aromatic ferrocenes was developed through the enantioselective cationic Au(i)-catalyzed cycloisomerization, in the presence of bidentate phosphine ligand (R)-DTBM-Segphos, from readily available ortho-alkynylaryl ferrocenes under very mild conditions (11 examples, up to 92% yield and 93% ee).

Enantioselective Synthesis of Four Stereoisomers of Sulfinyl Ferrocenyl Quinones with Central, Planar, and Helical Chirality.

Four stereoisomers of sulfinyl ferrocenyl-substituted helicenequinones having central, planar, and helical elements of chirality were stereoselectively formed, in one step, from reaction between enantiopure sulfinyl ferrocenyl dienes and a sulfinyl quinone. Asymmetric synthesis, kinetic resolution, or chemical resolution processes occurred in sequential cycloaddition, sulfoxide elimination, and partial aromatization steps.