Metal Catalyzed Redox Reactions

Metal Catalyzed Redox Reactions

Nathan Jui

MacMillan Group Meeting

January 27, 2010


! Many metal-catalyzed reactions involve redox processes

Cross-Coupling Chemistry

X

MR

catalyst R

Heck-Type Chemistry

Ar X

R

catalystAr

R

Reduction Chemistry

R

catalystMe

X

H2Me

R

X

DG catalyst DG

[O] R

Oxidation Chemstry

! These reactions and their mechanisms will not be addressed


! Many metal-catalyzed reactions involve redox processes

Constraints Applied

1. Catalytic in metal

2. Single electron transfer processes

3. Net redox neutral (no terminal oxidant)

4. No light (purely chemical activation)

5. Selective generation of organic radicals

If electron transfer is accompanied occurs via inner-sphere mechanism

Atom Transfer Radical Chemistry

S X

Mn+1X S

R

Mn+1XRS

RS

ATRA

Cycle

Mn

X

Radical Addition Mechanism as First Defined

! The 'Peroxide Effect' as observed by Kharasch and co-workers (1933)

Meroom temp

HBr H3C Me

Brsole product

Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major

"The presence of benzoyl peroxide or ascaridole modified profoundly the course of the

addition and the product of the reaction was largely, if not all, normal propyl bromide"

-Morris Kharasch

Kharasch, M. S. J. Am. Chem. Soc. 1933, 55, 2531.



Meroom temp

HBr H3C Me

Brsole product

Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major



-Morris Kharasch




Meroom temp

HBr H3C Me

Brsole product

Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major



-Morris Kharasch



! The 'Peroxide Effect' independantly defined by Kharash et al. as well as Hey and Waters (1937)

Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major

"...it may be suggested that the addition process is one requiring the transient

production of neutal atoms of hydrogen and broming from hydrogen bromide"

-Hey and Waters

Hey, D.; Waters, W. Chem. Rev. 1937, 21, 1969.

BzO H Br Br MeMe

Br H Br

Kharasch, M. S. J. Org. Chem. 1937, 2, 288.



Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major

Kharasch, M. S. et al. Science, 1945 122, 108.


! Kharasch later reported the radical addition of halomethanes to olefins (1945)

CCl4 Cl3CCl

MeMe

> 60% yield

(BzO)2, heat



Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major

"...it may be suggested that the addition process is one requiring the transient

production of neutal atoms of hydrogen and broming from hydrogen bromide"

-Hey and Waters

Hey, D.; Waters, W. Chem. Rev. 1937, 21, 1969.

BzO H Br Br MeMe

Br H Br




Meroom temp

HBr, ROORH3C Me

BrMe

Br

minor major

Kharasch, M. S. et al. Science, 1945 122, 108.


! Kharasch later reported the radical addition of halomethanes to olefins (1945)

CCl4 Cl3CCl

MeMe

> 60% yield

(BzO)2, heat

The Kharasch Addition Reaction of Halomethanes to Olefins

! Kharasch reported the radical addition of carbon-based radicals to olefins (1945)

Kharasch, M. S. Science 1945, 122, 108.

CCl4Cl3C

ClMe

MeAcO OAc

!

2 H3C 2 CO2AcO OAc

H3C CCl4 CH3Cl Cl3C

Cl3C R RCl3C

RCl3C CCl4

RCl3C

ClCl3C

RCl3C R Cl3C

R

R

Initiation

Propagation

PolymerizationR = Ar

The Kharasch Addition Reaction of Halomethanes to Olefins

! Kharasch reported the use of several radical electrophiles in his new radical reaction

OMehex

Cl

JACS, 1945, 1626

(AcO)2, 40% yield

hex

BrCBr3

h!, 88% yield

JACS, 1946, 154

hex

BrCCl3

(AcO)2, 78% yield

JACS, 1947, 1105

O

ClClOEt

hex

Br

JACS, 1948, 1055

(AcO)2, 54% yield

O

Halogen was used in excess (3- or 4-fold) for optimum yields

Higher order products made up mass balances

Highly activated bromomethanes were the best substrates

Ph

BrCBr3 Cl

PhCCl3Ph

CCl4, (AcO)2CBr4, light

quant96% n

The Failed Polymerizations of Minisci

! Surprisingly, substantial monoadduct formation was observed with carbon tetrachloride

Cl

CNCCl3

NC

nautoclave, 160 °C

CCl4, ROOR NC

ClCCl3

'significant amount'

H

CNCCl3

NC

nautoclave, 160 °C

CHCl3, ROOR NC

ClCHCl2

new regioisomer

! Standard peroxide initiated radical mechanisms occur via hydrogen abstraction

RO H CCl3NC

CCl3NC

CCl3H

Cl3C

Cl3C

NC

H CCl3

Minisci, F. Chem. Ind. (Milan), 1956, 122, 371.

Complete selectivity for opposite regioisomer suggested a new mechanism

Radical Chain Termination by Metal Halide Salts (Jay Kochi)

! Also in 1956, Kochi was studying the oxidation of alkyl radicals by metal salts

Kochi, J. J. Am. Chem. Soc. 1956, 78, 4815.

PhN2Cl CuCl or FeCl2

acetone

Ph

Cl

CuCl

Ph CuCl2

Ph

Cl CuCl

!CuCl

RR

Meerwein Arylation

1. The rate of benzylic radical oxidation by CuCl2 (or FeCl3) is much faster than styrene addition

2. Oxidation occurs through a 'ligand transfer' mechanism (inner-sphere electron transfer)

good yields

0% polymer

Minisci's reaction could have contained metal halides

Accidental Discovery of Catalytic Atom Transfer Radical Chemstry

! Minisci's steel autoclave was corroded and had likely leached iron into the reaction

Asscher, M. et al. J. Chem. Soc. 1963, 1887.

2 CCl4 Fe (s) 2 Cl3C FeCl2

CCl4 FeCl2 Cl3C FeCl3

! Minisci's group and Vofsi and Asscher first describe catalytic atom transfer radical addition

and could have been oxidized to FeCl3 by chlorine radicals

Cl

Cl

ClCl R

1 equiv 2 equiv

1 mol% CuCl (or FeCl2)

2 equiv solvent, 80!120 °C

RCl3C

Cl

46-89% yield

Ph CN CO2Et C6H13

Minisci, F. et al. Gazzeta 1961, 91, 1030.

Proposed Mechanism of Atom Transfer Radical Addition (ATRA)

! Metal catalyst participates in both initiation and termination steps, relative rates dictate selectivity

Figure adapted from: Matyjaszewski, K. et al. Chem. Soc. Rev. 2008, 1087.

CuIX

CuIIX2R

R R'

RR'

R

RR'

R

RR'

X

R'

RR'

R'n

R R

R X

RR'

RR'

R'R

telomer

polymer

ka1 kd2

kadd

kt kt

kt

kp

Selective ATRA Requires:

1. Low radical concentration

kd1 and kd2 >> ka1 and ka2

kd1 ka2

2. Slow product activation (vs sm)

ka1 >> ka2

3. Oxidation must be fast vs prop.

kd2 >> kp

monoadduct! Red. halogen abstraction

generates radical

! Oxid. halogen abstraction

terminates radical

Catalytic Redox Mechanism:

So Many Different Catalysts...

Y XR

Y R

XYYY Y MLnXn

(cat.)

! The many metals that catalyze CHCl3, CHBr3, CCl4, and/or CBr4 radical addition

! The most commonly used catalysts for ATRA reactions are CuIX and RuIIX2 derivatives

! Exact nature of free radical intermediates is not known

Evaluation of the Proposed Radical Mechanism

! Kharasch systems likely proceed via radical intermediates (Ru, Cu, Fe, Mo, Cr)

Matsumoto, H. et al. Tetrahedron Lett. 1975, 15, 899.

! Metal catalyst impacts diastereoselectivity of CCl4 addition to cyclohexene

CCl4 hex

RuCl2(PPh3)3

galvinoxyl hex

ClCl3C

80 °C, 4 h

0% yield

(76%, no spintrap)

Matsumoto, H. et al. Tetrahedron Lett. 1973, 14, 5147.

RuCl2(PPh3)3

80 °C, 4 h

(BzO)2

80 °C, 4 h

CCl4CCl3

Cl

CCl3

Cl

77% yield96:4 (trans:cis)

low yield53:47 (trans:cis)

Effect not seen with Cu: Asscher, M. et al. J. Chem. Soc. Perkin Trans. 2 1973, 1000.

CCl4

Intermediate radical species likely exist as coordinated radical pairs (Ru system)

Attempts at Enantioselective Kharasch Addition

! Chiral ligands could potentially induce enantioselectivity

Similar result with RhCl-diop system: Murai, S. et al. Angew. Chem. Int. Ed. Eng. 1981, 20, 475.

CCl4Ru2Cl4(diop)3

Ph

Cl

100 °C, 6 hPh CCl3

73% yield

13% ee

Kamigata, N. et al. Bull. Chem. Soc. Jpn. 1987, 60, 3687.

RuL*nCl2

RuIIICl3Cl3CRuIIICl3Cl3CCH2CHPh

CCl4

Ph

Ph

ClCl3C

L* = (!)-diop

O

OMe

Me

CH2PPh2

CH2PPh2

H

H

! Coordinated metal-radical pair should participate in enantiodetermining chlorination

ATRA

Cycle

Selected Examples of Atom Transfer Radical Addition Chemistry

! Area 1. Intramolecular Atom Transfer Reactions (ATRC)

X

X

ML2Xn

(cat.)FG

FG

! Area 2. Intermolecular Kharasch Type Haloalkylation Reactions

FG X RML2Xn

(cat.)

R

X

FG

Selected Intramolecular ATRA: 5-Exo Trig Cyclizations

! A variety of cyclization substrates and catalytic systems have been developed over 35+ years

Weinreb, S. et al. J. Org. Chem. 1990, 55, 1281.

Cl ClCl RuCl2(PPh3)3

PhH, 155 °C79% yield

MeO2C ClCl RuCl2(PPh3)3

PhH, 165 °C77%, 1:1 dr

MeO2C ClMe RuCl2(PPh3)3

PhH, 165 °C71%, 2:1 dr

MeO2C HMe

Cl

MeO2C HCl

Cl

ClCl

Cl

O

Cl ClCl CuCl

MeCN, 110 °C95% yield O

ClCl

Cl

OO

NH

Cl ClCl CuCl

MeCN, 140 °C57% yield N

H

ClCl

Cl

OO

NH

F BrF CuBr

MeCN, 80 °C84% yield N

H

FF

Br

OO

Clark, A. Chem. Soc. Rev. 2002, 31, 1.

1-10% typical loadings, > 80°C temperatures ~30% typical loading, > 100°C temperatures

RuCl2(PR3)3 catalysts: 1973 (Nagai) CuX catalysts: 1963 (Asscher & Vofsi)

Intramolecular Atom Transfer Radical Cyclization Ligand Effects

! 5-Exo trig cyclization of unsaturated !-haloamide substrates yields lactam scaffolds

Clark, A. Tetrahdron Lett. 1999, 40, 4885.

N

X ClCl

OTs

NTs

O

ClCl Cl30 mol% catalyst

solvent, temp

Catalyst Solvent Temp. Time Yield

CuCl MeCN 80 °C 24 h 97%

CuCl-bipy (5%) CH2Cl2 23 °C 0.2 h 91%

CuCl-bipy CH2Cl2 23 °C 24 h 0%

X

Cl

Cl

H

CuCl-NPMI CH2Cl2 23 °C 72 h 15%H

CuCl-tren-Me6 CH2Cl2 23 °C 2 h 90%H

NN

bipy

NN

NPMI

Me

N

Me2N

NMe2 NMe2

tren-Me6

Radical-Polar Crossover Mechanism: Addition to Enamides

! Electrophilic radicals add to acyl enamines, terminate via radical-polar crossover mechanism

Clark, A. Tetrahdron Lett. 1999, 40, 4885.

N

Me BrMe

OBn

NBn

O

MeMe30 mol% CuBr•L

CH2Cl2, rt, 20 minN

Me2N

NMe2 NMe2

82%, 1:1 ratio

= L

N

MeMe

OBn

NBn

O

MeMeCuLBr

!CuLBr2 NBn

O

MeMe

!H+CuLBr2

!CuLBr

N

Cl ClCl

OBn

NBn

O

ClCl30 mol% CuBr•L

CH2Cl2, rt

! While this triethylenetetramine ligand is highly active, the perfect Cu system remains unknown

0% yieldcomplex mixture

Cascade Cyclization Using Copper Redox Catalyst

! Radical mono- and bicyclization utilizing copper-bipy as catalyst (Dan Yang)

Yang, D. et al. Org. Lett. 2006, 8, 5757.

OEt

OO

ClClMe

Me

O

MeCl

CO2Et

ClMe

OEt

OO

ClCl

OCO2Et

Cl

Me MeCl

OEt

OO

ClCl

OCl

CO2Et

Me Me

Cl

CuCl•bipy

DCE, 80 °C21 h

61%

2:1 dr

33%

3:2 dr

! Bicyclization under the conditions outlined above give modest yields and diastereocontrol

79% yield

3:1 dr

Intramolecular Atom Transfer Radical Cyclization

! Medium ring heterocycle formation via redox reaction affords 8 and 9 membered lactones

Clark, A. et al. J. Chem. Soc. Perkin Trans. 1, 2000, 671.

O Cl3

O

30 mol% CuCl-bipy

0.1 M DCE80 °C, 18 h

O O

Cl

ClCl

nn

n = 1: 60% yield

n = 2: 59% yield

! Macrocyclization reactions were also accomplished using a tridentate ligand

Pirrung, F. et al. Synlett. 1993, 50, 739.

OO

O

OO

OO

O

OO CCl3

OClCl

Cl

10 mol% CuCl-ligand

0.2 M DCE, 80 °C70% yield

O

NN N

N


! Area 1. Intramolecular Atom Transfer Radical Addition Reactions (ATRC)

X

X

ML2Xn

(cat.)FG

FG

! Successful radical precursors in ATRC reactions so far are highly activated

n nn= 0-13

RO

O

R2N

O

R2N

O

RO

ONR2

ClRO

OOR

ClCl

ClCl

Cl

ClCl

F

IF

R2N

O

Cl

RCl

R2N

O

Cl

HCl

R2N

O

Cl

MeMe

R Cl

ClCl

RO

O

R

ClCl



X

X

ML2Xn

(cat.)FG

FG


n nn= 0-13

RO

O

R2N

O

R2N

O

RO

ONR2

ClRO

OOR

ClCl

ClCl

Cl

ClCl

F

IF

R2N

O

Cl

RCl

R2N

O

Cl

HCl

R2N

O

Cl

MeMe

R Cl

ClCl

RO

O

R

ClCl



X

X

ML2Xn

(cat.)FG

FG

! Area 2. Intermolecular Kharasch Addition Reactions of Polyhaloalkanes

n nn= 0-13

ML2Xn

(cat.)R

R'

R

R'

Y Y

X

Y

Y

X

Perfluoroalkylation of Olefins Using ATRA

! Kamigata's group describe a ruthenium catalyzed radical trifluromethylation protocol

1 mol% RuCl2(PPh3)2

benzene, 120 °C

Kamigata. J. Chem. Soc. Perkin Trans. 1. 1991, 627.

RF3C

SCl

O O

RCF3

Cl

1 equiv 2 equiv

! The reaction works well with highly activated olefins but is sensitive to sterics (1,2-substitution)

CF3

Cl

79% yield

41% yield

CF3

Cl

87% yield

CF3

Cl

66% yield

O2N

CF3

Cl

46% yield

CF3

Cl

23% yield

Me

Me

CF3

ClO

OEt

RuL*nCl2

RuIIICl3CF3RuIIICl3

F3CSO2Cl

R

Ph

ClF3C

ATRA

Cycle

SO2

R

CF3

Perfluoroalkylation of Olefins Using ATRA


1 mol% RuCl2(PPh3)2

benzene, 120 °C

Kamigata. J. Chem. Soc. Perkin Trans. 1. 1991, 627.

RF3C

SCl

O O

RCF3

Cl

1 equiv 2 equiv

! The reaction works well with highly activated olefins but is sensitive to sterics (1,2-substitution)

CF3

Cl

79% yield

41% yield

CF3

Cl

87% yield

CF3

Cl

66% yield

O2N

CF3

Cl

46% yield

CF3

Cl

23% yield

Me

Me

CF3

ClO

OEt

Arene Perfluoroalkylation Using Sulfonyl Chloride Reagents


1 mol% RuCl2(PPh3)2

benzene, 120 °C

Kamigata. N. J. Chem. Soc. Perkin Trans. 1. 1994, 1339.

F3CS

Cl

O O

1 equiv 2-5 equiv

! Benzene substrates react but are completely regio-permiscuous

53% yield

trace

41% yield

63% yield

RR

CF3

CF3

CF3 CF3

OMe

CF3

2:1:1 (o:m:p)36% yieldCF3

Me1:1:1 (o:m:p)

CN Me

Me39% yieldCF3

Br1:1:1 (o:m:p)



1 mol% RuCl2(PPh3)2

benzene, 120 °C


F3CS

Cl

O O

1 equiv 2-5 equiv

! Five-membered heterocyclic compounds work with increased regiocontrol

R RCF3

O CF3 S CF3 S CF3 S CF3Me OHC

N CF3 N CF3

BnN CF3

AcN CF3

COPh

30% 77% 73% 26%

0% 53% 61% 92%

H



1 mol% RuCl2(PPh3)2

benzene, 120 °C


F3CS

Cl

O O

1 equiv 2-5 equiv

! Benzene substrates react but are completely regio-permiscuous

53% yield

trace

41% yield

63% yield

RR

CF3

CF3

CF3 CF3

OMe

CF3

2:1:1 (o:m:p)36% yieldCF3

Me1:1:1 (o:m:p)

CN Me

Me39% yieldCF3

Br1:1:1 (o:m:p)

Trifluoromethylation of Electron-Poor Enolsilane Substrates

! Ruthenium catalyzed sulfonyl chloride decomposition also works on silyl enol ethers

1 mol% RuCl2(PPh3)2

benzene, 120 °C

Kamigata. N. Phosporus, Sulphur, and Silicon 1997, 155.

F3CS

Cl

O O

1 equiv 2 equiv

R

OTMSR

OCF3R'

R'

OCF3

OCF3

O2N Cl

OCF3

OCF3

MeO

55% yield 51% yield 58% yield 0% yield

Ph

OCF3 H

OCF3

OCF3 O

CF3

28% yield 35% yield 43% yield 0% yield

Me BntBu

Ph

Atom Transfer Radical Addition Reactions With Titanium Enolates

! Zakarian group published the first highly diastereoselective intermolecular Kharasch addition

Zakarian, A. et al. J. Am. Chem. Soc. 2010, ASAP.

O N

O

PhR

R

OR'

TiCl4

O N

O

PhR

R

OR'

O N

O

PhR

R

OR'

CCl3

TiCl4, i-Pr2NEt, CH2Cl2BrCCl3 (3 equiv)

7 mol% RuCl2(PPh3)3

45 °C, 12 h

O N

O

PhR

R

OR'

TiCl4

RuIIRuIII + Br

BrCCl3CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3




O N

O

PhR

R

OR'

TiCl4

O N

O

PhR

R

OR'

O N

O

PhR

R

OR'

CCl3


7 mol% RuCl2(PPh3)3

45 °C, 12 h

O N

O

PhR

R

OR'

TiCl4

RuIIRuIII + Br

BrCCl3CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

Bn

OMe

CCl3

O N

O

BnMeMe

O

CCl3O N

O

BnMeMe

O

CCl3

O N

O

BnMeMe

OC4H9

CCl3O N

O

BnMeMe

O

CCl3O N

O

BnMeMe

O

CCl3

TsN

6

4OBn

89%, >98:2 dr

99%, >98:2 dr

63%, >98:2 dr

87%, >98:2 dr

91%, >98:2 dr

61%, >98:2 dr




O N

O

PhR

R

OR'

TiCl4

O N

O

PhR

R

OR'

O N

O

PhR

R

OR'

CCl3


7 mol% RuCl2(PPh3)3

45 °C, 12 h

O N

O

PhR

R

OR'

TiCl4

RuIIRuIII + Br

BrCCl3CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

PhR

R

OR'

TiCl4

CCl3

O N

O

BnMeMe

O

MeO N

O

BnMeMe

O

Me

O N

O

BnMeMe

O

MeO N

O

BnMeMe

O

MeO N

O

BnMeMe

O

Me

64%, >98:2 dr

71%, 1.6:1 dr

83%, >98:2 dr

76%, >98:2 dr

71%, >98:2 dr

75%, 1.3:1 dr

O N

O

BnMeMe

O

MeCl

Cl

CF3

Cl

Me

Cl Cl

ClOMe

O

Cl Cl

OEt

O

OCO2Bn

Cl Cl

Atom Transfer Radical Polymerization (ATRP)

! In 1995, Krzysztof Matyjaszewski and Mitsuo Sawamoto picked up where Minisci left off (1956)

MatyjaszewskiSawamoto

Carnegie MellonKyoto University

! They independantly reported a new method (ATRP or living radical polymerization)

submitted September 6, 1994 submitted February 16, 1995

'Living Radical Polymerization' 'Atom Transfer Radical Polymerization'

Macromolecules, 1995, 28, 1721. J. Am. Chem. Soc., 1995, 117, 5614.

cited 2,374 timescited 1,571 times






















CuIX

CuIIX2R

R R'

RR'

R

RR'

R

RR'

X

R'

RR'

R'n

R R

R X

RR'

RR'

R'R

teleomer

polymer

ka1 kd2

kadd

kt kt

kt

kp



kd1 and kd2 >> ka1 and ka2 kd1 ka2


ka1 >> ka2


kd2 >> kp

monoadduct

Polymerization Can Occur If:

1. Above requirements are met

2. Starting Halogen is consumed




CuIX

CuIIX2R

R R'

RR'

R

RR'

R

RR'

X

R'

RR'

R'n

R R

R X

RR'

RR'

R'R

teleomer

polymer

ka1 kd2

kadd

kt kt

kt

kp





ka1 >> ka2


kd2 >> kp

monoadduct







CuIX

CuIIX2R

R'

RR'

RR'

X

R'

RR'

R'n

R X

polymer

ka1 kd2

kadd

kp





ka1 >> ka2


kd2 >> kp

monoadduct




P X MnXn P MnXn

+m


! Matyjaszewski polymerized styrene using a copper chloride bipy system

Matyjaszewski, K. et al. J. Am. Chem. Soc. 1995, 117, 5614.

PhMe Ph

Cl

1 equiv 0.01 equiv

1 mol% CuCl

3 mol% bipy130 °C, 3 h

Cl

Ph

Ph

Me

n PDI = 1.3!1.4595% consumption

! PDI = polydispersity index, a measure of how consistent chain growth is

! PDI equal to one: all of the chains in a given sample are of the same length

! Good PDI values are typically > 1.5

PDI = Mn / Mw

Mn = number average molecular weight

Mw = weight average molecular weight

total weight / number of molecules

average weight of average molecule




PhCl Ph

Me

1 equiv 0.01 equiv

1 mol% CuCl


Cl

Ph

Ph

Me

PDI = 1.3!1.4595% consumption

! Sawamoto system utilized some well-developed ruthenium phosphine conditions

CO2Me

1 equiv 0.01 equiv

0.5 mol% RuCl2(PPh3)3

2.0 mol% MeAl(OAr)2toluene, 60 °C, 4 h

ClCCl3


Me

CCl4

n

Me CO2Me

! Upon complete conversion, more monomer was added and completely incorporated

! Radical scavengers completely inhibited / stopped reactions

! Addition of different monomers allowed for 'Block polymers' (""""####)

Sawamoto, M. et al. Macromolecules 1995, 28, 1721.




PhCl Ph

Me

1 equiv 0.01 equiv

1 mol% CuCl


Cl

Ph

Ph

Me



CO2Me

1 equiv 0.01 equiv



ClCCl3


Me

CCl4

n

Me CO2Me








PhMe Ph

Cl

1 equiv 0.01 equiv

1 mol% CuCl


Cl

Ph

Ph

Me





PDI = Mn / Mw








PhMe Ph

Cl

1 equiv 0.01 equiv

1 mol% CuCl


Cl

Ph

Ph

Me





PDI = Mn / Mw








PhCl Ph

Me

1 equiv 0.01 equiv

1 mol% CuCl


Cl

Ph

Ph

Me



CO2Me

1 equiv 0.01 equiv



ClCCl3


Me

CCl4

n

Me CO2Me






Matyjaszewski, K. et al. Chem. Rev. 2001, 101, 2921.

P X MnX / Ligand P Mn+1X2 / Ligand+m

I X MnX / Ligand I Mn+1X2 / Ligand

m

I X Initiator (Alkyl Halide)

MnX / Ligand Catalyst

m monomer

redox potential

unique ATRP keq

solubilities, redox potentials

termination

kact

kdeact

kp

kt

! Different ATRP systems possess discrete rate properties based on the following





m

termination

kact

kdeact

kp

kt

! Different ATRP systems possess discrete rate properties based on the following! Each monomer has a specific keq (kact/kdeact) and requires specific conditions for ATRP

R

O OR O OR

Me

NN

! Only copper catalysts have been successful in polymerizing all of the above classes





m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


P





m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


P

M X





m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


PX





m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN

! Initiators tend to look like the desired monomer units (similar redox, kinetic properties)

PX X X X X




m

termination

kact

kdeact

kp

kt


R

O OR O R

X

NN

PX X X X

CuX CuX, RuX2, NiX2 NiX2, RuX2 FeX2, CuX CuX

! Metals typically used to initiate each indicated monomer class (ligands play huge role)




m

termination

kact

kdeact

kp

kt


R

O OR O R

X

NN

PX X X X



+1 V -1 V0

FeIII(phen)3 RuCl2(PPh3)3 CuCl(bipy)2 CuCl(Me6-tren)

0.5 -0.5 (vs SCE)

N NN

Me2N

NMe2 NMe2

N

N

N N

CuCl(TPA)RuClCp*PPh3

RuBrCp*PPh3

more stable cations

faster ATRP catalysts





m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


PX X X X X




m

termination

kact

kdeact

kp

kt


R

O OR O R

X

NN

PX X X X



+1 V -1 V0


0.5 -0.5 (vs SCE)

N NN

Me2N

NMe2 NMe2

N

N

N N


RuBrCp*PPh3

more stable cations






m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


PX X X X X




m

termination

kact

kdeact

kp

kt


R

O OR O R

X

NN

PX X X X



+1 V -1 V0


0.5 -0.5 (vs SCE)

N NN

Me2N

NMe2 NMe2

N

N

N N


RuBrCp*PPh3

more stable cations






m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


PX X X X X




m

termination

kact

kdeact

kp

kt


R

O OR O R

X

NN

PX X X X



+1 V -1 V0


0.5 -0.5 (vs SCE)

N NN

Me2N

NMe2 NMe2

N

N

N N


RuBrCp*PPh3

more stable cations






m

termination

kact

kdeact

kp

kt


R

O OR O OR

Me

NN


PX X X X X

New Catalyst Systems Allow for ATRA Reactions Under Mild Conditions

! Newer highly active ruthenium catalysts initiate rapidly at room temperature

Severin, K. Chem. Eur. J. 2007, 6899.

RuPh3P Cl

Cl

Mg powder

0.1 mol% catalyst EtO

O

HCl

Ph

Cl

24 h, 97% yield

PhEtO

OCl

Cl

toluene, rt2 equiv 1 equiv

5% RuCl2(PPh3)3: 155 °C, 16 h: 71% yield

New Catalyst Systems Allow for ATRA Reactions Under Mild Conditions

! Newer highly active ruthenium catalysts initiate rapidly at room temperature

Severin, K. Chem. Eur. J. 2007, 6899.

RuPh3P Cl

Cl

Mg powder

0.1 mol% catalyst EtO

O

HCl

Ph

Cl

24 h, 97% yield

PhEtO

OCl

Cl

toluene, rt2 equiv 1 equiv

5% RuCl2(PPh3)3: 155 °C, 16 h: 71% yield



X

X

ML2Xn

(cat.)FG

FG


n nn= 0-13

RO

O

R2N

O

R2N

O

RO

ONR2

ClRO

OOR

ClCl

ClCl

Cl

ClCl

F

IF

R2N

O

Cl

RCl

R2N

O

Cl

HCl

R2N

O

Cl

MeMe

R Cl

ClCl

RO

O

R

ClCl

Potential Future Atom Transfer Radical Chemistry

R

R'

O OR

R'

O R

Br R'

N

R'

N

Br Br Br BrMe

Potential Future Atom Transfer Radical Chemistry

R

R'

O OR

R'

O R

Br R'

N

R'

N

Br Br Br BrMe

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Metal Catalyzed Redox Reactions

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