Traceless Chelation‐Controlled Rhodium‐Catalyzed Intermolecular Alkene and Alkyne Hydroacylation

Abstract

A new functional-group tolerant, rhodium-catalyzed, sulfide-reduction process is combined with rhodium-catalyzed chelation-controlled hydroacylation reactions to give a traceless hydroacylation protocol. Aryl- and alkenyl aldehydes can be combined with both alkenes, alkynes and allenes to give traceless products in high yields. A preliminary mechanistic proposal is also presented.

Iridium‐Catalyzed Formyl‐Selective Deuteration of Aldehydes

“…[5] Importantly,this proposed ligand-controlled pathway would also avoid the need for an additional directing group on the aryl ring of the substrate. [6] To initiate our studies,w es creened as mall number of iridium complexes with large/large and large/small ligand pairs.U sing 2-naphthaldehyde (1)a samodel substrate,w e first examined the large/large ligand partnership,u sing precatalysts of the type [(COD)Ir(L 1 )(L 2 )]PF 6 ,w hich are commonly used in ortho-directed aryl labeling (Scheme 2). [2i, 7] In accordance with earlier stoichiometric tritiation work, [3a,b] the use of Crabtreesc atalyst (2) [8] led to appreciable levels of labeling across both the aromatic and formyl positions.…”

“…We hypothesized, therefore,t hat as maller, cis-enabled ligand pair would facilitate axial aldehyde binding and subsequent formyl CÀHa ctivation (Path B). [6] To initiate our studies,w es creened as mall number of iridium complexes with large/large and large/small ligand pairs.U sing 2-naphthaldehyde (1)a samodel substrate,w e first examined the large/large ligand partnership,u sing precatalysts of the type [(COD)Ir(L 1 )(L 2 )]PF 6 ,w hich are commonly used in ortho-directed aryl labeling (Scheme 2). [6] To initiate our studies,w es creened as mall number of iridium complexes with large/large and large/small ligand pairs.U sing 2-naphthaldehyde (1)a samodel substrate,w e first examined the large/large ligand partnership,u sing precatalysts of the type [(COD)Ir(L 1 )(L 2 )]PF 6 ,w hich are commonly used in ortho-directed aryl labeling (Scheme 2).…”

A rhodium-catalysed Sonogashira-type coupling exploiting C–S functionalisation: orthogonality with palladium-catalysed variants

“…11 Reports of desulfitative alkynylation are rare, and involve activation of the sulfide component, 12 metallated alkynes, 13 or are the result of the coupling of alkynyl thioethers with organometallic reagents. 14 Our laboratory has recently demonstrated that, in combination with a suitable directing group, it is possible to use Rh-bisphosphine complexes to selectively activate the C-S bond of arylmethylsulfides, to effect carbothiolation reactions, 15 reductive desulfurisations, 16 or Suzuki-type cross coupling reactions (Scheme 1). 17 As full selectivity for C-S functionalisation over C-X functionalisation was in each case observed, we envisaged that Scheme 1 Existing C-S activation methodologies and proposed chemoselective Sonogashira-type coupling.…”

Iridium‐Catalyzed Formyl‐Selective Deuteration of Aldehydes

“…We hypothesized, therefore, that a smaller, cis ‐enabled ligand pair would facilitate axial aldehyde binding and subsequent formyl C−H activation (Path B) . Importantly, this proposed ligand‐controlled pathway would also avoid the need for an additional directing group on the aryl ring of the substrate …”