The manganese(II)complex[Mn(SiNSi)Cl_(2)](SiNSi=2,6-[EtNSi(NtBu)_(2)CPh]_(2)C_(5)H_(3)N)is an efficient catalyst for the chemoselective C(sp)–H borylation of terminal alkynes.Aliphatic and aromatic alkynes with diffe...The manganese(II)complex[Mn(SiNSi)Cl_(2)](SiNSi=2,6-[EtNSi(NtBu)_(2)CPh]_(2)C_(5)H_(3)N)is an efficient catalyst for the chemoselective C(sp)–H borylation of terminal alkynes.Aliphatic and aromatic alkynes with different substituents have been efficiently borylated.Mechanistic studies indicate that the precatalyst enters the cycle by reaction with HBPin(Pin=pinacolate),which plays a key role in enabling a high chemoselective process.展开更多
The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBP...The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBPin).2-fluoro and 2,6-difluoropyridines were hydrodefluorinated at the 2-and 6-positions at room temperature in 3 h 30 min.The impact of the number of fluorine atoms and their position at the pyridyl ring in the efficiency of the catalyst was explored.Mechanistic experiments for the hydrodefluorination of 2,6-difluoropyridine allowed to identify COD decoordination followed by C–F oxidative addition as the catalyst entry pathway to the cycle and the[Ni(^(iPr)PN)(COD)]complex as the catalyst resting-state.The Ni(Ⅱ)fluoride complexes,[NiF(^(iPr)PN)(6-Fpy)](6-Fpy=6-fluoropyrid-2-yl)and[NiF(^(iPr)PN)(py)](py=2-pyridyl)were independently synthesized and identified as intermediates in the two subsequent hydrodefluorination cycles operative through single-turnover experiments.Both Ni(Ⅱ)fluoride complexes were found to be bench-stable precatalysts for the process with a comparable efficiency to[Ni(^(iPr)PN)(COD)]in the presence of a substoichiometric amount of COD to prevent catalyst deactivation.展开更多
The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temp...The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temperature.The system showed a broad substrate scope,including OMe and NH2 substituted pyridines,and enabled the C(sp^(2))-X HDH of several environmental pollutants and the DDF of CF_(3) groups and C(sp^(2))-X bonds in pyridines,affording CD_(3)-substituted pyridines with d incorporation at the CD_(3) group in>99% and high degrees of d incorporation at the ring.Mechanistic studies for the HDF of 2-trifluoromethylpyridine allowed the identification of three simultaneous HDF cycles,with the first cycle being the rate-determining and the reaction of the[Ni(COD)_(2)]precatalyst with the H source being the entry pathway to the cycle.The key behind catalyst efficiency for exhaustive HDH and its broad substrate scope has been traced back to the use of KOtBu,which enabled hydride transfer from NH_(3)BH_(3) to the[Ni(COD)_(2)]precatalyst,rendering access to a nickelate(0)hydride complex responsible for C-F activation.Competition experiments employing pyridines allowed the rationalization of catalyst selectivity for different types of C(sp^(2))-X bonds and for C(sp^(2))-F vs.C(sp^(3))-F bonds,as well as the impact of the position of CF_(3) groups on catalyst efficiency.展开更多
基金the ACS Petroleum Research Fund for a Doctoral New Investigator grant(PRF#66750-DNI3)UC Merced for start-up funds(SUP0000078).
文摘The manganese(II)complex[Mn(SiNSi)Cl_(2)](SiNSi=2,6-[EtNSi(NtBu)_(2)CPh]_(2)C_(5)H_(3)N)is an efficient catalyst for the chemoselective C(sp)–H borylation of terminal alkynes.Aliphatic and aromatic alkynes with different substituents have been efficiently borylated.Mechanistic studies indicate that the precatalyst enters the cycle by reaction with HBPin(Pin=pinacolate),which plays a key role in enabling a high chemoselective process.
基金supported by funds from the NSF LEAPS-MPS-CHE program(grant#2316526 to R.A.)the NSF MRI program(CHE-2216471)University of California,Merced,start-up funds for Rebeca Arevalo.
文摘The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBPin).2-fluoro and 2,6-difluoropyridines were hydrodefluorinated at the 2-and 6-positions at room temperature in 3 h 30 min.The impact of the number of fluorine atoms and their position at the pyridyl ring in the efficiency of the catalyst was explored.Mechanistic experiments for the hydrodefluorination of 2,6-difluoropyridine allowed to identify COD decoordination followed by C–F oxidative addition as the catalyst entry pathway to the cycle and the[Ni(^(iPr)PN)(COD)]complex as the catalyst resting-state.The Ni(Ⅱ)fluoride complexes,[NiF(^(iPr)PN)(6-Fpy)](6-Fpy=6-fluoropyrid-2-yl)and[NiF(^(iPr)PN)(py)](py=2-pyridyl)were independently synthesized and identified as intermediates in the two subsequent hydrodefluorination cycles operative through single-turnover experiments.Both Ni(Ⅱ)fluoride complexes were found to be bench-stable precatalysts for the process with a comparable efficiency to[Ni(^(iPr)PN)(COD)]in the presence of a substoichiometric amount of COD to prevent catalyst deactivation.
基金Victor Duran Arroyo and Roger Nunez for a generous gift of[Ni(^(iPr)PN)(COD)]the NSF for a LEAPS-MPS grant(#2316526)the University of California,Merced,for start-up funds.
文摘The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temperature.The system showed a broad substrate scope,including OMe and NH2 substituted pyridines,and enabled the C(sp^(2))-X HDH of several environmental pollutants and the DDF of CF_(3) groups and C(sp^(2))-X bonds in pyridines,affording CD_(3)-substituted pyridines with d incorporation at the CD_(3) group in>99% and high degrees of d incorporation at the ring.Mechanistic studies for the HDF of 2-trifluoromethylpyridine allowed the identification of three simultaneous HDF cycles,with the first cycle being the rate-determining and the reaction of the[Ni(COD)_(2)]precatalyst with the H source being the entry pathway to the cycle.The key behind catalyst efficiency for exhaustive HDH and its broad substrate scope has been traced back to the use of KOtBu,which enabled hydride transfer from NH_(3)BH_(3) to the[Ni(COD)_(2)]precatalyst,rendering access to a nickelate(0)hydride complex responsible for C-F activation.Competition experiments employing pyridines allowed the rationalization of catalyst selectivity for different types of C(sp^(2))-X bonds and for C(sp^(2))-F vs.C(sp^(3))-F bonds,as well as the impact of the position of CF_(3) groups on catalyst efficiency.
