transition metal catalyzed trifluoromethylation of unactivated alkene presented by ala bunescu...
TRANSCRIPT
Transition metal catalyzed trifluoromethylation of
unactivated alkene
Presented by Ala Bunescu
30/04/2013
Why CF3?• Important impact in pharmaceutic, agrochemistry and material science:
– before 1957 no F-containing drug had been developed, our days 150 fluorinated drugs have come to market
– ~20% of all pharmaceuticals; ~30% for agrochemicals
F3C
F3C
NO2
NO2
N
O
HN O
ClF3C N N
SO2NH2
HN O
CF3
EfavirenzHIV1 treatment
Celecoxibnon-steroidal
anti-inflammatory
Fluoxetine (Prozac) antidepressant
Trifluralin herbicide
~
Diederich- Science 2007, 317, 1881; J. T. Welch, Tetrahedron 1987, 43, 3123.
What is so special about CF3?
• F enhance metabolic stability (mainly by lowering the susceptibility to cytochrome P450 enzymatic oxidation)
• Enhance protein–ligand interactions• Increased lipophilicity• High elecrtonegativity (perturbation of pKa neighbor group,
impact on bioavailability) • Small size (2.5 x Me)• Improve thermal, chemical stability of materials
Diederich, Science 2007, 317, 1881; Gouverneur, Chem. Soc. Rev. 2008, 37, 320; McClinton-Tetrahedron,1992, 6555
Methods to introduce CF3
• Nucleophilic • Electrophilic• Radical
O OHCF3
"CF3-" nucleophile
G. K. S. Prakash, A. K. Yudin, Chem. Rev. 1997, 97, 757; Y. Kobayashi, Tetrahedron Lett. 1979, 20, 4071; Prakash Org. Lett. 2003, 5, 3253–3256;Y. Chang, Tetrahedron Lett. 2005, 46, 3161–3164.
"CF3+" electrophile
sources of CF3-:
Ruppert's reagent: CF3TMS/ nBu4NF
PhSO2CF3 / tBuOK,
CF3CO2Na/ CuI
Kobayasy's "CuCF3 system"
O O
CF3
Y
CF3X-
R
R
R
R
Y= S, Se, Te; X= OTf, BF4
Umemoto's reagents
T. Umemoto, Tetrahedron Lett. 1990, 31, 3579; Togni, Chem. Eur. J. 2006, 12, 2579
OIF3C
X
X= O, CF3
Togni' reagents
M
- McMillan α-Trifluoromethylation of Aldehydes via Photoredox Organocatalysis
"CF3." radical
Rf-I, lightCF3
CF3I
O O
CF3
CF3I, Et3B,airMI
Ogawa-J. Org. Chem. 2004, 69, 6658; Mikami-Org. Lett., 2005,22, 4883;
McMillan-JACS, 2009, 10875
Trifluoromethylation of unactivated double bonds
• Halotrifluoromehylation • Hydrotriflorometylation• Allylic CF3• Oxytrifluoromethylation
Iodotrifluoromethylation of double bond (ATRA)
T. Fuchikami, I. Ojima, Tetrahedron Lett. 1984, 25, 303–306
Fe3(CO)12Co2(CO)8 Pd(PPh3)4
Ni(CO)2(PPh3)2 Mo(CO)5PPh3
Ag/Al2O3
ATRA: atom transfer radical addition
Iodotrifluoromethylation of double bond (ATRA)
Proposed Mechanism
Sthephenson-JACS, 2012, 8875
Chlorotrifluoromethylation (ATRA)
Yoshida- J. Chem. Soc. Perkin Trans. 1 1991, 627Kamigata J. Chem. Soc. Chem. Commun. 1989, 1559
Hydrotrifluoromethylation of unactivated double bonds
Gouverneur-JACS, 2013, 2505
Qing-ACIE, 2013,2198
Hydrotrifluoromethylation double bonds: Ru
S
CF3
Umemoto's reagents
BF4
from carvone
from quinine
Gouverneur-JACS, 2013, 2505
Hydrotrifluoromethylation of unactivated double bonds: Ru
Gouverneur-JACS, 2013, 2505
Reduction potential Umemeto reagent: -0.25VRu(bpy)3(II): 0.77VMeOH: 1.5 V
Proposed Mechanism
Hydrotrifluoromethylation of unactivated double bonds: Ag
ConditionsAgNO3(0.1 mmol), CF3SiMe3(4eq), 1,4-CHD (1 eq)PhI(OAc)2 (2eq), NaOAc (2eq) NMP, rt, N2
Qing-ACIE, 2013,2198
from 4-methyl umbelliferone
from isopulegol
from estrone
from alkyne
Hydrotrifluoromethylation of unactivated double bonds: Ag
Qing-ACIE, 2013,2198
Proposed Mechanism
Copper catalyzed allylic trifluoromethylation
Jianbo Wang-JACS, 2011,16410
Buchwald –ACIE, 2011, 9120
15 examples 44%-97%
Liu-JACS, 2011,15300,
, DMAc
S OCu
O N
0.1eq 2equiv
Copper catalyzed allylic trifluoromethylation
Buchwald
- high selectivity for the linear trifluoromethylation (in contrast to Kharasch–Sosnovsky-type oxidative alkene functionalizations)
formation of an free allylic radical is unlikely to occur
Copper catalyzed allylic trifluoromethylation
Wang
• CF3 radical involved • allyl radical wasn’t trapped using TEMPO
no evidence of the involvement of eitherallylmetal species or trifluoromethylmetal
species in the mechanism.
Copper catalyzed allylic trifluoromethylation
Heck like four memebered ring TS
regioselectivity
LiuCu(I)/ Cu(III)
Direct protonation:
Oxytrifluoromethylation of unactivated double bonds
Akita- ACIE 2012,9567
Buchwald- JACS, 2012, 12462
Sodeoka-TL, 2012, 5503Szabo-OL, 2012, 2882
Three-component Oxytrifluoromethylation of Alkenes Mediated by Photoredox Catalysts
OIF3C
O
Togni' reagents
Buchwald- JACS, 2012, 12462
Three-component Oxytrifluoromethylation of Alkenes Mediated by Photoredox Catalysts
S
CF3
Umemoto's reagents
BF4
Akita- ACIE 2012,9567
Linear alkene doesn’t react
Oxytrifluoromethylation of unactivated double bonds
Akita- ACIE 2012,9567
Kharasch–Sosnovsky