Rhodium-Catalyzed Rearrangement of Aryl Bis(alkynyl) Carbinols to 3-Alkynyl-1-indanones

Rhenium-Promoted C-C Bond-Cleavage Reactions of Internal Propargyl Alcohols

The first examples of C-C bond cleavage reactions of internal propargyl alcohols to give vinylidene complexes are described. Treatment of [Re(dppm)₃ ]I with RC≡CC(OH)R'R'' (R=aryl, alkyl; C(OH)R'R''=C(OH)Ph_2, C(OH)Me₂ , C(OH)HPh, C(OH)H₂ ) produced the vinylidene complexes ReI(=C=CHR)(dppm)₂ with the elimination of C(O)R'R''. Computational studies support that the reactions proceed through a β-alkynyl elimination of alkoxide intermediates Re{OC(R')(R'')C≡CR}(dppm)₂ .

The isomerization of allylrhodium intermediates in the rhodium-catalyzed nucleophilic allylation of cyclic imines

Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4-rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene-rhodium complexes.

Catalytic 1,4-rhodium(III) migration enables 1,3-enynes to function as one-carbon oxidative annulation partners in C-H functionalizations

1,3-Enynes containing allylic hydrogens cis to the alkyne are shown to act as one-carbon partners, rather than two-carbon partners, in various rhodium-catalyzed oxidative annulations. The mechanism of these unexpected transformations is proposed to occur through double C-H activation, involving a hitherto rare example of the 1,4-migration of a Rh(III) species. This phenomenon is general across a variety of substrates, and provides a diverse range of heterocyclic products.

Iridium-catalyzed arylative cyclization of alkynones by 1,4-iridium migration

1,4-Metal migrations enable the remote functionalization of C-H bonds, and have been utilized in a wide variety of valuable synthetic methods. The vast majority of existing examples involve the 1,4-migration of palladium or rhodium. Herein, the stereoselective synthesis of complex polycycles by the iridium-catalyzed arylative cyclization of alkynones with arylboronic acids is described. To our knowledge, these reactions involve the first reported examples of 1,4-iridium migration.