Allylrhodium Species Research Articles

Remote Nucleophilic Allylation by Allylrhodium Chain Walking.

Metal migration through a carbon chain is a versatile method for achieving remote functionalization. However, almost all known examples involve the overall net migration of alkylmetal species. Here, we report that allylrhodium species obtained from hydrorhodation of 1,3-dienes undergo chain walking toward esters, amides, or (hetero)arenes over distances of up to eight methylene units. The final, more highly conjugated allylrhodium species undergo nucleophilic allylation with aldehydes and with an imine to give Z-homoallylic alcohols and amines, respectively.

ChemInform Abstract: Chain Walking of Allylrhodium Species Towards Esters During Rhodium‐Catalyzed Nucleophilic Allylations of Imines.

AbstractThe Rh‐catalyzed reaction of imines (I) and (VIII) with allyltrifluoroborates (II) is accompanied by isomerization of the Rh‐intermediates to afford homoallylic sulfamates (III) and (IX).

Chain Walking of Allylrhodium Species Towards Esters During Rhodium-Catalyzed Nucleophilic Allylations of Imines.

Allylrhodium species derived from δ‐trifluoroboryl β,γ‐unsaturated esters undergo chain walking towards the ester moiety. The resulting allylrhodium species react with imines to give products containing two new stereocenters and a Z‐alkene. By using a chiral diene ligand, products can be obtained with high enantioselectivities, where a pronounced matched/mismatched effect with the chirality of the allyltrifluoroborate is evident.

Chain Walking of Allylrhodium Species Towards Esters During Rhodium‐Catalyzed Nucleophilic Allylations of Imines

AbstractAllylrhodium species derived from δ‐trifluoroboryl β,γ‐unsaturated esters undergo chain walking towards the ester moiety. The resulting allylrhodium species react with imines to give products containing two new stereocenters and a Z‐alkene. By using a chiral diene ligand, products can be obtained with high enantioselectivities, where a pronounced matched/mismatched effect with the chirality of the allyltrifluoroborate is evident.

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.

Desymmetrizations of meso-tert-norbornenols by rhodium(i)-catalyzed enantioselective retro-allylations

Rhodium-catalyzed desymmetrizations of meso-tert-norbornenols by retro-allylations generate allyl-rhodium species that allow for a rich and diverse downstream reactivity.

Rhodium‐Catalyzed Allylation of Aldehydes with Homoallylic Alcohols by Retroallylation and Isomerization to Saturated Ketones with Conventional or Microwave Heating

The treatment of an aldehyde with a tertiary homoallylic alcohol at 100-250 degrees C in the presence of cesium carbonate and a rhodium catalyst leads to allyl transfer from the homoallylic alcohol to the aldehyde. The process includes Rh-mediated retroallylation to form an allyl rhodium species as the key intermediate. The homoallylic alcohol formed initially through allyl transfer is converted under the reaction conditions into the corresponding saturated ketone when bulky ligands are used. Microwave heating at 250 degrees C accelerates the reaction significantly.

Rhodium-catalyzed allyl transfer from homoallyl alcohols to acrylate esters via retro-allylation

Retro-allylation of homoallyl alcohols by rhodium catalysts occurs to generate allylrhodium species. Insertion of acrylate esters to the allylrhodiums proceeds to give the corresponding 2,5-hexadienoate esters in situ. Subsequent isomerization or iterative 1,4-addition takes place in the same pots to furnish the corresponding 2,4-hexadienoate esters or triesters in good yields.

Rhodium-Catalyzed Allyl Transfer from Homoallyl Alcohols to Aldehydes via Retro-Allylation Followed by Isomerization into Ketones

Retro-allylation of homoallyl alcohol by rhodium catalysis occurs to generate allylrhodium species. This allylrhodium reacts with aldehydes to give the corresponding secondary alcohols in situ. Isomerization of these alcohols proceeds in the same pots to furnish the corresponding saturated ketones in good yields. [reaction: see text]