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1
Gold CatalysisGold Catalysis
Federica Stazi Ph.D.
Literature Meeting
Montréal, 11th April 2006
2
OutlineOutline
• General properties of gold:General properties of gold: - - The element - - Facts and myths
• Heterogeneous catalysis (briefly):Heterogeneous catalysis (briefly): - - Main characteristics
- - Examples: ethyne hydrochlorination, oxidations, hydrogenation, …
• Homogeneous catalysisHomogeneous catalysis - - Overview - - Gold as an oxidant - - Gold as an Lewis Acid
- - C-H activation
- - Alkyne activation
- - Allene activation
- - Asymmetric reaction
- - Recent literature
• ConclusionConclusion
• Questions?Questions?
3
Gold: The ElementGold: The Element
11
4
Gold: The ElementGold: The Element
• Name: from the Sanskrit word Jval and the Anglo-Saxon gold.
Gold’s chemical symbol comes from the Latin word Aurum. Known
for at least 5500 years.
• Sources: generally in conjunction with silver, quartz (SiO2), calcite (CaCO3), lead,
tellurium, zinc or copper. 2/3 of the world’s gold comes from South Africa. It is
present in sea water: about 0.1 to 2 mg/ton, but no isolation method has been
developed.
• Characteristic: most malleable and ductile metal, good conductor of heat and
electricity, not attacked by oxygen or sulfur. Reacts with halogens (e.g. aqua regia
dissolved gold). Soft metal, so it is alloyed with others metals like Ag, Cu, Pt and Pd
to increase the strength (e.g. application in jewelry).
• Applications: the isotope Au-198 (half-life 2.7 days) used for treating cancer.
AuNa3O6S4 (gold sodium thiosulfate) used for arthritis. HAuCl4 (chlorauric acid)
used to preserve photographs by replacing the silver atoms.
5
Gold: The ElementGold: The Element
• Electron configuration: [Xe] 6s1 4f14 5d10
• Oxidation States: from –I to III and +V
• Most common Gold (I) and Gold (III) complex, both used in homogeneous catalysis.
• Prices for 1g (STREM catalog 2004-06):
AuAu Pd Pd
PtPt RhRh RuRu
AuCl
86$
AuBr3
55$
HAuCl440$
PtCl 70$
PtO2
76$
Pt
110$
PdCl238$
Pd(OAc)2
52$
Pd2(dba)3
66$
RhCl(PPh3)
42$
RhCl3
136$
Rh(acac)2
134$
very
expensive
c.f. Christopher’s
presentation
PPh3AuCl 125$ (Alfa Aesar)
6
Gold: Facts and MythsGold: Facts and Myths
FALSE: • Gold is chemically inert and uninteresting
• Gold is expensive (cheaper than Platinum)
TRUE: • Gold is stable in the presence of oxygen and water
• Gold can be used for heterogeneous and homogeneous catalysis
“The use of gold as a catalyst is desirable when it shows similar activity as for a more
expensive catalyst or higher selectivity than a less expensive catalyst and when a new
transformation is possible”.
When is it convenient to use gold as a catalyst? (A. S.K. Hashmi Gold Bull. 2004, 51-65)
7
OutlineOutline
• General properties of gold:General properties of gold: - - The element - - Facts and myths
• Heterogeneous catalysis (briefly):Heterogeneous catalysis (briefly): - - Main characteristics
- - Examples: ethyne hydrochlorination, oxidations, hydrogenation, …
• Homogeneous catalysisHomogeneous catalysis - - Overview - - Gold as an oxidant - - Gold as an Lewis Acid
- - C-H activation
- - Alkyne activation
- - Allene activation
- - Asymmetric reaction
- - Recent literature
• ConclusionConclusion
• Questions?Questions?
8
HeterogeneousHeterogeneous Catalysis
Key Features: Key Features: • Particle size (1 and 10 nm in diameter)
• Nature of the support (transition metal oxide, carbon, zeolite)
Active Catalyst: supported small metallic gold particles
Advantages:Advantages: • High catalytic activity (small amounts are necessary)
• Mild conditions (low temperature, low pressure)
• Good resistance to deactivation
INDUSTRIAL APPLICATIONSINDUSTRIAL APPLICATIONS
G. J. Hutchings Catal. Today 2005, 55-61; C. W. Corti, R. J. Holliday, D. T. Thompson Catal. Today 2005, 253-261.
9
Heterogeneous CatalysisHeterogeneous Catalysis
1.1. Ethyne (acetylene) Hydrochlorination Ethyne (acetylene) Hydrochlorination
Cl+ HClAu/C
180 ºC
G. J. Hutchings J. Catal. 1985, 292-295; G. J. Hutchings Gold Bull. 1996, 123.
PVC market
Advantages: • 3x more reactive than the traditional HgCl2
• catalyst recycling
2. CO Oxidation at Low Temperature
CO CO2
air
CatalystIndustrial, environmental and domestic sectors
M. Haruta, T. Kobayashi, H. Sano, N. Yamada Chem. Lett. 4, 1987, 405.
Catalyst: Hopcalyte (mixed oxide of Mn and Cu)Anhydrous conditions necessary
Not active at ambient temperature
Au/Fe2O3 or Co3O4
More active and stable
Activity at -70 ºC
10
Heterogeneous CatalysisHeterogeneous Catalysis
3. Oxidations Mediated by O3. Oxidations Mediated by O22
High temperatures are necessary (270 - 720 ºC) and product mixtures are observed.
OHOH
OHO
O
Na+O2 3 atm, NaOH aq 0.4 M
Catalyst
Catalyst: 1% Au/C (reagent/catalyst= 1000) conversion: 96% selectivity: 98%
1% Au/TiO2 conversion: 95% selectivity: 98%
5% Pd or Pt/C selectivity: 77%
OH
NH2
O
O
NH2
Na+O2 3 atm, NaOH aq 0.4 M
Catalyst
1% Au/C conversion: 22% selectivity: 100%
1% Au/Al2O3 conversion: 100% selectivity: 100%
5% Pd or Pt/C no reaction
S. Biella, G.L. Castiglioni, C. Fumagalli, L. Prati, M. Rossi Catal. Today 2002, 43-49.
11
Heterogeneous CatalysisHeterogeneous Catalysis
3. Oxidations Mediated by O3. Oxidations Mediated by O22
S. Carrettin, P. McMorn, C. Fumagalli, P. Johnston, K. Griffin, G. J. Hutchings Chem. Commun. 2002, 696-697.
1% Au/graphite
conversion: 56%selectivity: 100%
O2 3 atm, NaOH aq
60ºC, 3h
5% Pt/C
conversion: 88%
55%
23%
O2 6 atm, NaOH aq
60ºC, 3h
selectivity: 63%
12
Heterogeneous CatalysisHeterogeneous Catalysis
4. Selective Hydrogenation (under H4. Selective Hydrogenation (under H22 pressure) pressure)
P. Claus Appl. Catalysis A: General 2005, 222-229.
Extended studies on the size particles, supports and synthesis technique on the selectivity.
13
Heterogeneous CatalysisHeterogeneous Catalysis
4. Selective Hydrogenation4. Selective Hydrogenation
S. Schimpf, M. Lucas, C. Mohr, U. Rodemerck, A. Bruckner, J. Radnik, H. Hofmeister, P. Claus Catal. Today 2002, 63-78.
Au/SiO2 Pt, Pd and Rh
14
Heterogeneous CatalysisHeterogeneous Catalysis
5. Industrial Application: Commercial Uses (Patent)5. Industrial Application: Commercial Uses (Patent)
C. W. Corti, R. J. Holliday, D. T. Thompson Appl. Catalysis A: General 2005, 253-261.
15
OutlineOutline
• General properties of gold:General properties of gold: - - The element - - Facts and myths
• Heterogeneous catalysis (briefly):Heterogeneous catalysis (briefly): - - Main characteristics
- - Examples: ethyne hydrochlorination, oxidations, hydrogenation, …
• Homogeneous catalysisHomogeneous catalysis - - Overview - - Gold as an oxidant - - Gold as an Lewis Acid
- - C-H activation
- - Alkyne activation
- - Allene activation
- - Asymmetric reaction
- - Recent literature
• Questions?Questions?
16
Homogeneous CatalysisHomogeneous Catalysis
Key Features:Key Features:
• Soft transition metal, soft partners such as carbon are preferred.
• Often reactions are faster than other transition metals. In some cases a completely new
product is formed.
• Organogold intermediates undergo fast protodemetallation.
• Cross-coupling chemistry seems difficult due to the easy reduction (difficult oxidation) of
gold.
• It has been shown that often reactions are possible with both Au (I) and Au (III), so the
real catalytic species is not known. On the other hand, in some cases different products
are observed for the different oxidation states.A. S.K. Hashmi Gold Bull. 2003, 3-9; A. S.K. Hashmi Gold Bull. 2004, 51-65; A. S.K. Hashmi Angew. Chem. Int. Ed. 2005, 44, 6990-6993.
A. Arcadi, S. Di Giuseppe Curr. Org. Chem. 2004, 8, 795-812; A. Hoffmann-Roder, N. Krause Org. Biol. Chem. 2005, 3, 387-391.
• Low propensity for β-H elimination.
17
Homogeneous CatalysisHomogeneous Catalysis
1.1. Gold as an oxidantGold as an oxidant
RS
R' RS
R'
O
5% Bu4N[AuCl4]
CH3NO2/ HNO376-97%
R= aryl or alkylR'= alkyl
ON
O
5% Na[AuCl4]
CH3NO2
+
35%
50 ºC
HNO3, NaNO2
F. Gasparrini, M. Giovannoli, D. Misiti, G. Natile, G. Palmieri Tetrahedron 1983, 39, 3181-3184 and 1984, 40, 165-170.
F. Gasparrini, M. Giovannoli, D. Misiti, G. Natile, G. Palmieri, L. Maresca J. Am. Chem. Soc. 1993, 115, 4401-4402.
O
O
O
5% AuCl3[OP(n-C12H25)3]
72%
5% AgSbF6/ [(H3C)3Si]O2
J. Sundermeyer, C. Jost DE 10041510 1999.
1.1 Thioether Oxidation
1.2 Oxidative Alkyne Coupling
1.3 Baeyer-Villiger Oxidation
18
Homogeneous CatalysisHomogeneous Catalysis
2. Gold as a Lewis Acid2. Gold as a Lewis Acid
R
O O
R
NHCBz
NH2
O
OBz
R
O
R
O NHCBz
CH2Cl2 r.t R= Ph 99%
+5% AuCl3.H2O
Me 65%
R= Ph 78%
S. Kobayashi, K. Kakumoto, M. Sugiura Org. Lett. 2002, 4, 1319-1320.
R R'
O O
R''NH
R''' R R'
N OR'''R''
5% NaAuCl4
EtOH r.t.
+
A. Arcadi, M. Chiarini, S. Di Giuseppe Green Chemistry 2003, 5, 64-67.
2.1 Michael Addition
2.2 Carbonyl-amine condensation
19
Homogeneous CatalysisHomogeneous Catalysis
2. Gold as a Lewis Acid (continue)2. Gold as a Lewis Acid (continue)
O NH
I
O
Ph
NH2 O
Ph
N
99%
CuI 10%ZnCl2 41%AgNO3 24%Na2PdCl4 60 %
90%
CH3COO- NH4+, Benzene reflux, AcOH 70%
62%
Benzene reflux, p-TsOH 61%
RR'
O
X
NH2
O
R''
R'
RN
R''
X
2.5% NaAuCl4
EtOH, r.t.
+
A. Arcadi, M. Chiarini, S. Di Giuseppe, F. Marinelli Synlett 2003, 203-206.
2.3 Friendländer Quinoline Synthesis
20
Homogeneous CatalysisHomogeneous Catalysis
2. Gold as a Lewis Acid (continue)2. Gold as a Lewis Acid (continue)
N
COOEt
Ph
N
Ph
COOMe
N
Ph
COOPh
N
Ph O
N
Ph
F
83%
CuI 0%ZnCl2 43%AgNO3 0%Na2PdCl4 0%
87% 62%
150 ºC, 4h 70% H2SO4, AcOH reflux 86%
87%
100-120 ºC, 80%
81%
A. Arcadi, M. Chiarini, S. Di Giuseppe, F. Marinelli Synlett 2003, 203-206.
21
Homogeneous CatalysisHomogeneous Catalysis
3. C-H Activation3. C-H Activation
NAu
ArCl
Cl
Ph
Ar
PhAuCl3ArH2,6-lutidine THF, 50 ºC
Ar= benzene, toluene, xylene, mesitylene, cumene, methoxybenzene, chlorobenzene
Y. Fuchita, Y. Utsunomiya, M. Yasutake J. Chem. Soc., Dalton Trans. 2001, 2330-2334.
Ar'
Ar
Ar'
Ph Ph
OH
Ph
Br
AuCl3 (1.5%)ArH
CH3NO2, 50 ºC
+AgSbF3 (3%)
16-95%
86% 90% 30%
Hydroarylation of Alkynes
M. T. Reetz, K. Sommer Eur. J. Org. Chem. 2003, 3485-3496.
22
Homogeneous CatalysisHomogeneous Catalysis
3. C-H Activation3. C-H Activation
PhAr
Ph
Ar H
[Au]
Ar
Ph
[Au]
COOEt
Ar COOEt
Ar H
L[Au]
Ar COOEt
L[Au]
L[Au]
[Au]
+ H+
+
(Z)+ H+
+
n+ (n-1)+
n+
+ +
+
2Z. Shi, C. He J. Org. Chem. 2004, 69, 3669-3671.
Proposed Mechanism:
COOEt
Ar COOEt2AuCl3 (5%)
ArH
DCE, r.t AgOTf (15%) 74-99%
+(Z)
or
1AuPPh3Cl (1%) BF3.OEt (15%) CH3NO2, r.t
1M. T. Reetz, K. Sommer Eur. J. Org. Chem. 2003, 3485-3496.
M. T. Reetz, K. Sommer Eur. J. Org. Chem. 2003, 3485-3496.
23
Homogeneous CatalysisHomogeneous Catalysis
3. C-H Activation3. C-H Activation
Z. Shi, C. He J. Org. Chem. 2004, 69, 3669-3671.
Z. Shi, C. He J. Am. Chem. Soc. 2004, 126, 5964-5965.
Y. Luo, C. -H. Li Chem. Comm. 2004, 1930-1931.
X. Yao, C. -H. Li J. Am. Chem. Soc. 2004, 126, 6884-6885.
Also applied to diene, triene and cyclic enol ethers!
Li and Al. Org. Lett. 2005, 7, 673-675.
24
Homogeneous CatalysisHomogeneous Catalysis
4. Alkynes Activation 4. Alkynes Activation
4.1 Nucleophilic Addition to Alkynes
1Y. Fukuda, K, Utimoto J. Org. Chem. 1991, 56, 3729-3731.
RRR
R
O
RR
OMeMeO
RR
O
RR
OMe
1Na[AuCl4] (2%)
H2O: MeOH (reflux)
> 90%
1Na[AuCl4] (2%)
MeOH (reflux) > 80%
90%
2[Au(PPh3)CH3] (2%)
MeOH (reflux)
H+
+
10%
2J. H Teles, S. Brode, M. Chabanas Angew. Chem. Int. Ed. 1998, 37, 1415-1418.
O-Nucleophile
N-Nucleophile
3Y. Fukuda, K, Utimoto Synthesis. 1991, 975-978.
TetrahydropyridineR'
NH2
R''
N
R'
R''
3Na[AuCl4] (5%)
CH3CN (reflux)
> 90%
25
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation 4. Alkyne Activation
4.1 Nucleophilic Addition to Alkynes
2A. Arcadi, G. Bianchi, F. Marinelli Synthesis 2004, 4, 610-618.
R
O
O
OR'
R
O
N
R''
OR'
N
R''
O
R
OR'
O
OR'
O
Na[AuCl4] (5%)
EtOH
+
50-100%
40 ºC
Na2PdCl2 (5%)EtOH 40 ºC
up to 70%
5-exo-dig
R= Me, Ph R'= Me, Et, Ph
R"NH2
R"= Ph, Bz, Ar, Ts, CH2COOEt
Pyrroles1
1A. Arcadi, S. Di Giuseppe, F. Marinelli, E. Rossi Adv. Syn. Catal. 2001, 5, 343-6346.
Indoles2
26
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation 4. Alkyne Activation
4.1 Nucleophilic Addition to Alkynes
Pyridines
G. Abbiati, A. Arcadi, G. Bianchi, S. Di Giuseppe, F. Marinelli, E. Rossi J. Org. Chem. 2003, 68, 6959-6966.
O
N N
PhN
N
Ph
N
O N
NH
NH
78% 78% 57%
60%
65%
27
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation 4. Alkyne Activation
4.1 Nucleophilic Addition to Alkynes
Pyridines
G. Abbiati, A. Arcadi, G. Bianchi, S. Di Giuseppe, F. Marinelli, E. Rossi J. Org. Chem. 2003, 68, 6959-6966.
NaAuCl4 2.5 %
EtOH reflux
46-98%
6-endo-dig
28
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
A. S. K. Hashmi, T. M. Frost, W. Bats J. Am. Chem. Soc. 2000, 122, 11553-11554.
4.2 Furan Isomerisation
R R
R
3 4
Same conditions!
R R
29
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
A. S. K. Hashmi, T. L. Ding, W. Bats, P. Fischer, W. Frey Chem. Eur. J. 2003, 9, 4339-4345.
4.2 Furan Isomerisation: Synthesis of Jungianol
75% 0% 0%
68% 21%7% Jungianol
30
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
N. Asao, T. Nogami, S. Lee, Y. Yamamoto J. Am. Chem. Soc. 2003, 125, 10921-10925.
4.3 Benzoannulation
AuX3
Cu(OTf)2
AuX3
1 3
11
31
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
4.4 5-exo-dig and 5-endo-dig Carbocyclisation
Conditions: 1% Au(PPh3)Cl, 1% AgOTf
CH2Cl2, r.t 5 min to 24 h
J. J. Kennedy-Smith, A. T. Staben, F. D. Toste J. Am. Chem. Soc. 2004, 126, 4526-4527.
1
2 34
5
5-exo-dig
93%5-exo-dig
32
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
4.4 5-exo-dig and 5-endo-dig Carbocyclisation
A. T. Staben, J. J. Kennedy-Smith, F. D. Toste Angew. Chem. Int. Ed. 2004, 43, 5350-5352.
1
2 3
45
5-endo-dig
33
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
4.5 Cycloisomerisation
C. Nieto-Oberhumber, M. Paz Munoz, E. Bunuel, C. Nevado, D. J. Cardenas, A. M. Echavarren Angew. Chem. Int. Ed. 2004, 43, 2402-2406.
34
Homogeneous CatalysisHomogeneous Catalysis
4. Alkyne Activation4. Alkyne Activation
4.5 Cycloisomerisation (continue)
2C. Nieto-Oberhumber, M. Paz Munoz, E. Bunuel, C. Nevado, D. J. Cardenas, A. M. Echavarren Angew. Chem. Int. Ed. 2004, 43, 2402-2406.
MeOOC
MeOOC
MeOOC
MeOOC OMe
MeOOC
MeOOC
MeOH (reflux)
AuCl3 (5%)1
16h
98%
[Au(PPh3)Me] (3%)2
MeOH, rt
97%
[Au(PPh3)Cl] (2%)2
25 min
4h
AgSbF6 (2%)
HBF4 (6%),
91%
1M. Mendez, M. Paz Munoz, E. Bunuel, C. Nevado, D. J. Cardenas, A. M. Echavarren J. Am. Chem. Soc. 2001, 123, 10510-10520.
97%
Au(I) Au(I) vs.vs. Au(III) Au(III)
PtClPtCl22 shows broader scope shows broader scope
35
Homogeneous CatalysisHomogeneous Catalysis
4. Alkynes Activation4. Alkynes Activation
4.5 Cycloisomerisation (Nolan)
97%
1P. De Frémont, N. M. Scott, E. D. Stevens, S. P. Nolan Orgaometallics. 2005, 24, 2411-2418. 2S. P. Nolan and al. Chem. Commun. (ASAP).
3 S. P. Nolan and al. Angew. Chem. Int. Ed. (on press).
N N
Au
Cl
[Au(IPr)Cl]
N-Heterocyclic Carbene Gold(I) Complex [Au(NHC)Cl]
36
Homogeneous CatalysisHomogeneous Catalysis
55. . Allene ActivationAllene Activation
5.1 Cycloisomerisation of α-hydroxyallenes1,2
1A. Hoffmann-Roder, N. Krause Org. Lett. 2001, 3, 2537-2538.
97%
2N. Krause, A. Hoffmann-Roder, J. Canisius Synthesis 2002, 12, 1759-1774.
Classical conditions: HCl(g) in CHCl3
or stoichiometric AgNO3
37
Homogeneous CatalysisHomogeneous Catalysis
55. . Allene ActivationAllene Activation
5.2 Cycloisomerisation of α-amino-1 and α-thio- allenes 2
1N. Morita, N. Krause Org. Lett. 2004, 6, 4121-2123.
97%
3-pyrrolines
2,5-dihydrothiophenes
2N. Morita, N. Krause Anew. Chem. Int. Ed. 2006, 45, 1897-1899.
AuCl (5%)88%
38
Homogeneous CatalysisHomogeneous Catalysis
55. . Allene ActivationAllene Activation
Proposed Mechanism:
97%
In the case of α-thioallenes more investigation are necessary to established the catalytic species!
39
Homogeneous CatalysisHomogeneous Catalysis
6. Asymmetric Reactions6. Asymmetric Reactions
R
O
CN
COOMe
NO
R COOMe
NO
R COOMe
N
PPh2
NMe2
PPh2
Fe
CH2Cl2 r.t
1% [Au(c-HexNC)2]BF4-
83-100%
+1% chiral ligand
dr 9:1, ee 96%chiral ligand =
I. Yoshihiko, M. Sawamura, T. Hayashi J. Am. Chem. Soc. 1986, 108, 6405-6406.
6.1 Asymmetric Aldol Condensation
Proposed transition state:
40
Homogeneous CatalysisHomogeneous Catalysis
6. Asymmetric Reactions6. Asymmetric Reactions
P. F. Hughes, S. H. Smith, J. T. Olson J. Org. Chem. 1994, 58, 5799-5802.
6.1 Asymmetric Aldol Condensation
threo-3-hydroxylysine
balanol
90%
dr 19:1%
ee > 99%
41
Homogeneous CatalysisHomogeneous Catalysis
6. Asymmetric Reactions6. Asymmetric Reactions
M.P. Munoz, J. Adrio, J.C. Carrettero, A.M. Echavarren Organometallics 2005, 24, 1293-1300.
6.2 Asymmetric Cycloisomerisation
5% PtCl2, MeOH, (S)-TolBINAP, 80ºC94%, 48% ee (-)
42
Homogeneous CatalysisHomogeneous Catalysis
6. Asymmetric Reactions6. Asymmetric Reactions
C. Gonzalez-Arellano, A. Corma, M. Iglesias, F. Sanchez Chem. Commun. 2005, 3451-3153.
6.3 Asymmetric Hydrogenation
43
Homogeneous CatalysisHomogeneous Catalysis
Recent Literature: Nucleophilic Attack to Unactivated Alkenes Recent Literature: Nucleophilic Attack to Unactivated Alkenes
1C.-G. Yang, C. He J. Am. Chem. Soc. 2005, 127, 6966-6967.
1 2
3
2J. Zhang, C.-G. Yang, C. He J. Am. Chem. Soc. 2006, 128, 1798-1799.
3C. Brouver, C. He Angew. Chem. Int. Ed. 2006, 45, 1744-1747.
44
ConclusionConclusion
Au (I) or Au (III)? Au (I) or Au (III)?
A. W. Someck, M. Rubina, V. Gevorgyan J. Am. Chem. Soc. 2005, 127, 10500-10501.
R R R
1 2 3AuCl3
Au(PEt3)Cl
Toluene, 5 min to 3 days
X X
XX= Cl, Br, I
45
[[[(Dimethylammino)methylene]amino]-methylene]dimethylammonium Chloride[[[(Dimethylammino)methylene]amino]-methylene]dimethylammonium Chloride11
Br
O
Br
O
N
NH2
O
Br
N
O
N
N+
N
NMe2Cl N
N
NMe2
NH
R
N
N
R
N
NMe2
GR, MeONa
MeOH, reflux
GR, i-PrONa
i-PrOH, reflux
74%
91%
RNH2 + +
It is a brown solid and it is a β-dimethylaminomethylenating agent for ketones and amines2
N+
N NCl
2J. T. Gupton, C. Colon, C. R. Harrison, M. J. Lizzi, D. E. Polk J. Org. Chem. 1980, 45, 4522-4524.
1Encyclopedia of Reagents for Organic Synthesis (Ed L.A. Paquette) Vol3, 1995, 2014.
Questions?Questions?
What is the What is the GoldGold’s reagent?’s reagent?
46
Questions?Questions?
What is the What is the difference between pink, yellow and white golddifference between pink, yellow and white gold??
Pink: Pink: alloy ofalloy of gold and coppergold and copper
White: White: alloy of gold, silver and palladium, coated with rhodiumalloy of gold, silver and palladium, coated with rhodium
Yellow: Yellow: alloy of gold with other metalsalloy of gold with other metals (Karat: measure of gold purity, 24K is pure (Karat: measure of gold purity, 24K is pure gold)gold)