Chiral gold(I) catalysts
have been designed based on a modified
JohnPhos ligand with a distal C
2-2,5-diarylpyrrolidine
that creates a tight binding cavity. The C
2-chiral element is close to where the C–C bond formation takes
place in cyclizations of 1,6-enynes. These chiral mononuclear catalysts
have been applied for the enantioselective 5-exo-dig
and 6-endo-dig cyclization of different 1,6-enynes
as well as in the first enantioselective total synthesis of three
members of the carexane family of natural products. Opposite enantioselectivities
have been achieved in seemingly analogous reactions of 1,6-enynes,
which result from different chiral folding of the substrates based
on attractive aryl–aryl interactions.
Gold(I)‐catalyzed cycloisomerizations of 1,n‐enynes proceed through electrophilic intermediates that can be trapped intra‐ or intermolecularly by a variety of hetero‐ and carbon nucleophiles to form complex skeletons in a single step. This review covers the efforts of our group towards the development of new reactions that have been successfully applied in the total synthesis of several natural terpenoids and related carbocyclic structures, as well as for the ready access to challenging linear acenes.
The photoredox-assisted gold-catalyzed arylative cyclization of 1,6-enynes with aryldiazonium salts gives rise to cyclization products with the opposite configuration at the alkene than that obtained by gold(I)-catalyzed alkoxycyclization. The reaction occurs under mild conditions and shows high functional group tolerance.
The ortho-alkynylation of nitro-(hetero)arenes takes place in the presence of a Rh(III) catalyst to deliver a wide variety of alkynylated nitroarenes regioselectively. These interesting products could be further derivatized by...
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