Faculty of Natural Sciences

TY - JOUR

T1 - Stoichiometric Studies on the Carbonylative Trifluoromethylation of Aryl Pd(II) Complexes using TMSCF3 as the Trifluoromethyl Source

AU - Domino, Katrine

AU - Johansen, Martin B.

AU - Daasbjerg, Kim

AU - Skrydstrup, Troels

PY - 2020/3/9

Y1 - 2020/3/9

N2 - We have performed a series of stoichiometric studies in order to identify viable steps for a hypothetical catalytic cycle for the palladium-mediated carbonylative coupling of an aryl bromide with TMSCF3. Our work revealed that benzoyl Pd(II) complexes bearing Xantphos or tBu(3)P as the phosphine ligands, which are generated from the corresponding Pd-II(Ph)Br complexes exposed to stoichiometric (CO)-C-13 from (13)COgen, were unable to undergo transmetalation and reductive elimination to trifluor-oacetophenone. Instead, in the presence of base and additional CO, these organometallic complexes readily underwent reductive elimination to the acid fluoride. Attempts to determine whether the acid fluoride could represent an intermediate for acetophenone production were unrewarding. Only in the presence of a boronic ester did we observe some formation of the desired product, although the efficiency of transformation was still low. Finally, we investigated the reactivity of four phosphine-ligated Pd-II(Ph)CF3 complexes (Xantphos, DtBPF, tBu(3)P, and triphenylphosphine) with carbon monoxide. With the exception of the tBu(3)P-ligated complex, all other metal complexes led to the facile formation of trifluoroacetophenone. We also determined in the case of triphenylphosphine that CO insertion occurred into the Pd-Ar bond, as trapping of this complex with n-hexylamine led to the formation of n-hexylbenzamide.

AB - We have performed a series of stoichiometric studies in order to identify viable steps for a hypothetical catalytic cycle for the palladium-mediated carbonylative coupling of an aryl bromide with TMSCF3. Our work revealed that benzoyl Pd(II) complexes bearing Xantphos or tBu(3)P as the phosphine ligands, which are generated from the corresponding Pd-II(Ph)Br complexes exposed to stoichiometric (CO)-C-13 from (13)COgen, were unable to undergo transmetalation and reductive elimination to trifluor-oacetophenone. Instead, in the presence of base and additional CO, these organometallic complexes readily underwent reductive elimination to the acid fluoride. Attempts to determine whether the acid fluoride could represent an intermediate for acetophenone production were unrewarding. Only in the presence of a boronic ester did we observe some formation of the desired product, although the efficiency of transformation was still low. Finally, we investigated the reactivity of four phosphine-ligated Pd-II(Ph)CF3 complexes (Xantphos, DtBPF, tBu(3)P, and triphenylphosphine) with carbon monoxide. With the exception of the tBu(3)P-ligated complex, all other metal complexes led to the facile formation of trifluoroacetophenone. We also determined in the case of triphenylphosphine that CO insertion occurred into the Pd-Ar bond, as trapping of this complex with n-hexylamine led to the formation of n-hexylbenzamide.

KW - ACID FLUORIDE

KW - BROMIDES

KW - CARBON-CARBON

KW - CATALYZED TRIFLUOROMETHYLATION

KW - CHLORIDES

KW - EX-SITU GENERATION

KW - FORMING REDUCTIVE ELIMINATION

KW - KETONES

KW - PD

KW - PHARMACEUTICALS

U2 - 10.1021/acs.organomet.9b00849

DO - 10.1021/acs.organomet.9b00849

M3 - Journal article

AN - SCOPUS:85080075520

VL - 39

SP - 688

EP - 697

JO - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 5

ER -