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Rhenium-Catalyzed Synthesis ofMultisubstituted Aromatic Compounds via
C-C Single-Bond Cleavage Kuninobu, Y.; Takata, H.; Kawata, A.; Takai, K. Org.
Lett. ASAP
Current LiteratureKalyani Patil
6/28/08
R6
R2
R4
R3
R1
R5
R1 OEt
O O
R2
+ R3 R4 + R5 R6cat. [ReBr(CO)3(thf)]2
Kalyani Patil @ Wipf Group Page 1 of 13 7/3/2008
Outline
• Synthesis of Substituted Aromatic Compounds
• Rhenium Catalyzed Reactions
• Rhenium Catalyzed C-H Activation - Takai Group
• Title Paper
• Summary
Kalyani Patil @ Wipf Group Page 2 of 13 7/3/2008
Synthesis of Substituted Aromatic CompoundsBergman cyclization
Vollhardt Angew. Chem. Int. Ed.1984, 23, 539
Trimerization of acetylenes
Bergman et. al. J. Am. Chem. Soc. 1972, 94, 660
R3
R4
R1
R2
150-200 °C
benzenecyclohexadiene
R3
R4
R1
R2
R1
R2
R3
R4
H
R1
R2
R3
R4
H
H
R1
R2
R3
R4
H
H
(CH2)n +
R1
R2
CpCo(CO)2
30 - 95%
R1
R2
CH2
MLxMLx-1
+ +MLx-2
MLx-2
+
MLx-2
1 2 3
4
MLx-2
5
+
6
MLx-2
• Oxidative coupling to give metallacyclopentadiene
• Alkyne insertion or Diels-Alder type addition
Kalyani Patil @ Wipf Group Page 3 of 13 7/3/2008
Synthesis of Substituted Aromatic CompoundsRing-closing metathesis
OH
n-Pr
n-Pr
On-Pr
n-Pr
Grubbs' II
CH2Cl2, rt, 2h
O
n-Pr
n-Pr
Danheiser et. al. J.Org. Chem.1984, 49, 1672
OCH3
+O
4 e- electrocyclic
cleavage
O
[2+2]
O
H3CO
4 e- electrocyclic
cleavage
O
H3CO
6 e- electrocyclic
closure
OH
H3CO
benzene, 80 °C, 26h
Annulation of vinylketenes with acetylenes
Imamoto et. al. J. Am. Chem. Soc.2005, 127, 10470
Kalyani Patil @ Wipf Group Page 4 of 13 7/3/2008
Properties of Rhenium
• Grayish white metal, last naturally occurring element to be discovered
• Discovered in 1925 by Dr. Walter Noddack and Dr. Ida Tacke Noddack
• Electronic configuration: [Xe] 4f14 5d5 6s2
• Oxidation states: -3, -1, 0, +1 to +7
• Lower electronegativity than Ru and Rh
Kalyani Patil @ Wipf Group Page 5 of 13 7/3/2008
Rhenium Catalyzed Reactions
Friedel-Crafts alkylation
+ t-BuClReBr(CO)5 (1 mol%)
ClCH2CH2Cl, 84 °C
OCH3 OCH3
t-Bu93%
Sonoda et. al. Bull. Chem. Soc. Jpn.2000, 73, 2779
Anti-Markovnikov addition of carboxylic acids to terminal alkynes
Ph + PhCOOHReBr(CO)5 (1 mol%)
toluene, 110 °CPh
O Ph
O
+ O Ph
O
Ph
67% 13:87
Hua et. al. J. Org. Chem.2004, 69, 5782
Coupling of epoxides with CO2
O
Ph
+ CO2ReBr(CO)5 (0.1 mol%)
110 °C, 85%O
O
O
Ph Hua et. al. J. Org. Chem.2005, 70, 381
Kalyani Patil @ Wipf Group Page 6 of 13 7/3/2008
Rhenium Catalyzed Reactions - Toste GroupEtherification of propargylic alcohols
Toste et. al. J. Am. Chem. Soc.2003, 125, 6076
n-Bu
OH
H
Ph
1 mol% (dppm)ReOCl3
Cl OH
MeCN, 65 °C n-Bu
O
H
Ph
Cl
78%
R2
OH
R1
X[M]
O
-HXR2
O
R1
[M]O
[3,3] R1
R2
O[M]
OH+
R1 R2
O
1 2
[O]
R2
O
R13 R2
OR3
R1
R3OH
Synthesis of 1,5-Enynes
Ph
OH
H
Ph
5 mol% (dppm)ReOCl3
MeNO2, 65 °C
PhH
Ph
79%
TMS+
cat. NH4PF6 Toste et. al. J. Am. Chem. Soc.2003, 125, 15760
Kalyani Patil @ Wipf Group Page 7 of 13 7/3/2008
Rhenium Catalyzed Ring Expansion - Takai Group
Takai et. al. J. Am. Chem. Soc.2006, 128, 12376
O O
R
n
+ Ph
[ReBr(CO)3(thf)]2 (2.5 mol%)
neat, 24h
PhCH2NC (5 mol%)
O
Ph
R
O
n
O PhO
OEt
O
Ph
O
OEt
O
Ph
OEt
O
O
Ph
O
87% 78% 78% 61%
O O
OEt
ReHO
OH O
OEt
O
R
OEt
O
HO
R
OEt
O
(4-b)
RHO
OEt
O
(3-b)
R
ReHO
R
OEt
O
(2-a)
R
OEt
O
Re (I)
(3-a)
ReO
R
OEt
O
(2-b)
(4-a)
Construction of medium size rings
Insertion of terminal alkynes into C-Cnext to the carbonyl group
• Rhenacyclopentene intermediate
• Retro-aldol reaction/isomerization
• Reductive elimination
Kalyani Patil @ Wipf Group Page 8 of 13 7/3/2008
Rhenium Catalyzed C-H Activation - Takai GroupFormation of indene derivatives
Takai et. al. Angew. Chem. Int. Ed.2006, 45, 2766
Takai et. al. J. Am. Chem. Soc.2005, 127, 13498
Synthesis of isobenzofuran
Takai et. al.J. Am. Chem. Soc.2006, 128, 12376
N
H
t-Bu
+ Ph Mecat. [ReBr(CO)3(thf)]2
toluene, reflux, 24h
HN
Ph
t-Bu
95%
O
+
cat. [ReBr(CO)3(thf)]2
toluene, 180 °C, 24hCO2Et
93%
CO2Et
p-anisidine (15 mol%)
Ph
N +
cat. [ReBr(CO)3(thf)]2
toluene, reflux, 24h O
Ph
Ph
93%
Ph
Ph
O
H
MS 4Å
Kalyani Patil @ Wipf Group Page 9 of 13 7/3/2008
Kuninobu, Y.; Takata, H.; Kawata, A.; Takai, K. Org. Lett. ASAP
Title Paper
R6
R2
R4
R3
R1
R5
R1 OEt
O O
R2
+ R3 R4
R5 R6
[ReBr(CO)3(thf)]2 (2.5 mol%)MS 4Å (200 wt%-Re cat.)
toluene, 180 °C, 24h
O
O
R2
R4
R3
R1toluene, 150 °C, 24h
Entry R1 R2 R3 R4 R5 R6 Yield (%)
1. Me Me Ph Ph CO2Et CO2Et 83
2. Ph Me Ph Ph CO2Et CO2Et 64
3. Me Ph Ph CO2Et CO2Et 84
4. Me Me Me Ph CO2Et CO2Et 91
H
5. Me Me Ph CO2Et CO2Et 87
6. Me Me n-C10H21 CO2Et CO2Et 72
7. Me n-C6H13 Ph CO2Et CO2Et 85, A:B = 96:4
8. n-C5H11 Me n-C6H13 Ph CO2Et CO2Et 83, A:B = 6:94
n-C5H11
H
H
9. Me Me Ph Ph CO2Et 83
10. Ph Me Ph Ph CO2Et 77, C:D = 39:61
H
H
CO2Et
n-C5H11
Ph
n-C6H13
EtO2C
CO2Et
Ph
n-C6H13
n-C5H11
EtO2C
CO2Et
Ph
Ph
Ph Ph
Ph
Ph
EtO2C
A B C D
Kalyani Patil @ Wipf Group Page 10 of 13 7/3/2008
DA w/ Benzyne
Kuninobu, Y.; Takata, H.; Kawata, A.; Takai, K. Org. Lett. ASAP
R OEt
O O [ReBr(CO)3(thf)]2 (2.5 mol%)MS 4Å (200 wt%-Re cat)
+Ph Ph
toluene, 180 °C
O
O
Ph
R Ph
SiMe3
OTf
1 (1eq.)
1 eq.
(1.5 eq.)
, CsF(3 eq.)
toluene/CH3CN, 20 °C, 12h
Ph
Ph
R
2
R time (h) yield (%)
Me (1a) 24 92 (2a)
Ph (1b) 48 96 (2b)
Title Paper
Intramolecular Reaction
OEt
O O
Ph
[ReBr(CO)3(thf)]2 (2.5 mol%)MS 4Å (100 wt%-Re cat)
toluene, 150 °C, 24h
O
O
Ph
MeO2C CO2Me
(4 eq.)
toluene, 150 °C, 48h
CO2Me
Ph
MeO2C
(84%)
Benzyne generated in situ tosynthesize naphthalene derivatives
Synthesis of tetrahydronaphthalene derivatives
Kalyani Patil @ Wipf Group Page 11 of 13 7/3/2008
Title Paper: Proposed Mechanism
Kuninobu, Y.; Takata, H.; Kawata, A.; Takai, K. Org. Lett. ASAP
R1
R2
O O
OEt R1
R2
OH O
OEt
(3-b)
R4
(2-a)
Re (I)
(3-a)
(2-b)
R3(1)
Re
R3
R4
R2R1O CO2Et
H
Re
R2
R1
O R3
CO2Et
R4
O
R1
R3
R4
OR2
H
EtO
R4R3
O CO2Et
R1 R2
H
O
O
R1
R3
R4
R2
(4)-EtOH
O
O
R4R3
R1
R2
R5
R6
(5) R5 R6
R6
R2
R4
R3
R1
R5(6)
-CO2• Rhenacyclopentene intermediate
• Retro-aldol reaction/reductive elimination
• Isomerization of the alkene/cyclization
• DA reaction/decarboxylation
Kalyani Patil @ Wipf Group Page 12 of 13 7/3/2008
Summary
• Synthesis of Multisubstituted Aromatic Compounds in Good Yields
• Products are Obtained in High Regioselectivity
• Aliphatic and Aromatic Acetylenes employed Prior to DA Reaction
Kalyani Patil @ Wipf Group Page 13 of 13 7/3/2008