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Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles.

ABSTRACT: The use of [Pd(NHC)(cinnamyl)Cl] precatalysts in the direct arylation of heterocycles has been investigated. Among four different precatalysts, [Pd(SIPr)(cinnamyl)Cl] proved to be the most efficient promoter of the reaction. The C-H functionalization of sulfur- or nitrogen-containing heterocycles has been achieved at low catalyst loadings. These catalyst charges range from 0.1 to 0.01 mol % palladium.

SUBMITTER: Martin AR

PROVIDER: S-EPMC3510996 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Comparison of the catalytic activity for the Suzuki-Miyaura reaction of (?(5)-Cp)Pd(IPr)Cl with (?(3)-cinnamyl)Pd(IPr)(Cl) and (?(3)-1-t-Bu-indenyl)Pd(IPr)(Cl).

Project description:Complexes of the type (?(3)-allyl)Pd(L)(Cl) and (?(3)-indenyl)Pd(L)(Cl) are highly active precatalysts for the Suzuki-Miyaura reaction. Even though allyl and indenyl ligands are similar to cyclopentadienyl (Cp) ligands, there have been no detailed comparative studies exploring the activity of precatalysts of the type (?(5)-Cp)Pd(L)(Cl) for Suzuki-Miyaura reactions. Here, we compare the catalytic activity of (?(5)-Cp)Pd(IPr)(Cl) (IPr = 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene, Cp) with two commercially available catalysts (?(3)-cinnamyl)Pd(IPr)(Cl) (Cin) and (?(3)-1-t-Bu-indenyl)Pd(IPr)(Cl) ( (tBu) Ind). We show that Cp gives slightly better catalytic activity than Cin, but significantly inferior activity than (tBu) Ind. This order of activity is rationalized by comparing the rates at which the precatalysts are activated to the monoligated Pd(0) active species along with the tendency of the starting precatalysts to comproportionate with monoligated Pd(0) to form inactive Pd(I) dimers. As part of this work the Cp supported Pd(I) dimer (?-Cp)(?-Cl)Pd2(IPr)2 (Cp (Dim) ) was synthesized and crystallographically characterized. It does not readily disproportionate to form monoligated Pd(0) and consequently Cp (Dim) is a poor catalyst for the Suzuki-Miyaura reaction.

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Direct Arylation of Benzo[<i>b</i>]furan and Other Benzo-Fused Heterocycles.

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