Catalytic Regio- and Enantioselective Proton Migration from Skipped Enynes to Allenes

Abstract

A catalytic enantioselective proton migration of skipped enynes to allenes is developed. A newly identified chiral ferrocenyl phosphine ligand plays critical roles in controlling both regio-and enantioselectivity. The method offers a new concept to convert readily available and abundant feedstock hydrocarbons into high-value-added molecules by reconstituting C-H bond connectivity without relying on polar functional groups.

Three-Component Borylallenylation of Alkynes: Access to Densely Boryl-Substituted Ene-allenes

“…Moreover, various naturally bioactive molecules contain ene-allene skeletons as core structures (Scheme ). Numerous methods have been developed for the synthesis of ene-allenes. − The γ-substitution of propargylic alcohol derivatives with nucleophilic reagents, the isomerization of skipped enynes, and the ring-closing metathesis of 1, n -allenyne are the most straightforward routes to ene-allenes. However, these methodologies often suffer from problems of functional group compatibility because presynthesized substrates and organo-metal reagents are used in these reactions.…”

Catalytic Regio‐ and Enantioselective Protonation for the Synthesis of Chiral Allenes: Synergistic Effect of the Counterion and Water

“…It is noteworthy that performing the reaction with water scavengers, such as Na 2 SO 4 or molecular sieves, resulted in the loss of reactivity (entry 13). These results implied that water was essential for the current transformation [17] and trace water in reaction system was able to execute proton transfer. The amount of exogenous water was examined as well.…”

Access to Divergent Fluorinated Enynes and Arenes via Palladium-Catalyzed Ring-Opening Alkynylation of gem-Difluorinated Cyclopropanes

“…Gladly, when KF was used, an almost-quantitative yield of 3a with high Z -selectivity was observed, and only trace amounts of isomers were detected (Table , entry 6). These results provide evidence that the choice of base is critical for this reaction, which due to the easy isomerization of the 1,4-enyne under base conditions (see the Supporting Information for more details) . Then, several palladium catalysts were examined in this reaction, and it was found that Pd­(OTFA) 2 proved to be the best catalyst.…”

“…Afterward, monofluorinated enynes generated through C–C bond elimination with released Pd catalyst for further catalytic steps. Isomerization of the skipped enyne 6a then can afford the enallene intermediate IV . Finally, intramolecular C–H bond activation and cyclization occurred, forming the product 7a .…”