Oxaziridines: New Perspectives and Insights
Konstantinos RampalakosMichigan State University
11/26/2003
Oxaziridines
ON
R''
R'
RFirst discovered by Emmons in 1957
(Emmons, W. D. J. Am. Chem. Soc. 1957, 79, 5739)
Strained three-membered ringWeak N-O bond Unusual Reactivity
Summary of Oxaziridines’ Reactivity
O N
C
Nu Nu
Nu
hv
Photochemical Rearrangements
O-transfer N-transfer
Outline
• Introduction• Heteroatom Transfer Reactions
N vs O Transfer: Mechanistic ConsiderationsO Transfer Reactions N Transfer Reactions
• Photochemical Rearrangement Reactions• Conclusion
Oxaziridines: Common Methods of Preparation
R'
O
R R'
HNOH2NOSO3H / OH-
R 50-73 %
(method prefered for N-H oxaziridines)
N
O
mCPBA56 %
N
O
O
K2CO3
NSO2
NOS
O2
KHSO5
9O %K2CO3
Andreae, S.; Schmitz, E. Synthesis 1991, 327-341
Davis, F. A.; Towson, J. C.; Weismiller, M. C.; Lal, S.; Carroll, P. J. J. Am. Chem. Soc. 1988, 110, 8477-8482Widmer, J.; Schierlein, W. K. Helv. Chim.Acta 1974, 57, 657-664
Mechanism of Imine Oxidation by Peroxy Acids
NR
ONHO
O
Ar
R NO
R
mCPBA
Two-stage mechanism (Baeyer-Villiger type)
slow fast
NR
mCPBAN
RO
O
H O
Ar
NO
R
Concerted mechanism
The two-stage mechanism is generallyaccepted for the reaction
Ogata,Y.; Sawaki, ,Y. J. Am. Chem. Soc. 1973, 95, 4687
Outline
• Introduction• Heteroatom Transfer Reactions
N vs O Transfer: Mechanistic ConsiderationsO Transfer Reactions N Transfer Reactions
• Photochemical Rearrangement Reactions• Conclusion
O-Transfer: Mechanistic Considerations
ρ = 0.55−1.03
NO
SO O X
Y
Nu "Nu O"
NuN
O
R R
RN
O
R R
R
R R
NR
"Nu O"
Mechanism for Oxygen Transfer to various Nucleophiles:
δ+
δ−
δ−Nu
Davis, F. A.; Billmers, J. M.; Gosciniak, D. J.; Towson, J. C. J. Org. Chem. 1986, 51, 4240-4245
N-Transfer: Mechanistic Considerations
ON
First stable N - transfer
O
OMe
ρ = 0.83
O N
O N NHMoc
oxaziridine
X
NuO
N ON
O"Nu NR"
Mechanism for Nitrogen Transfer to various Nucleophiles:
δ+
δ−
δ−Nu
R R
Vidal J.; Damestoy S.; Guy L.; Hanachi J,; Aubry A.; Collet A. Chem. Eur J. 1997, 3, 1691-1709
Rationalizing N vs O transfer: A Balance Between Electronics and Sterics
C
N O
Ph
CO
O
Me- 0.30
-0.24-O.26
+0.19-O.O6
C
N O
Ph
SOO
Me
+0.20
-0.25-0.02
-0.16
-0.16
Electronics: N is more e- defficient than O
Sterics: Bulky N-substituent can make the attack of Nu to N less favored
(O-transfer reagent)(N-transfer reagent)
Electronics: Nitrogen is more electron deficient than Oxygen
NNNNORNH2, RR’NH
O/NNOOOORSMe
00.61.21.82.52.52.54.8A value
HClCO2MeMeCF3Ph2POSO2MetBuN-substituent
Sterics: Nucleophilic attack to Nitrogen can be hindred
C
N O
Ph
CO
O
Me- 0.30
-0.24-0.26
+0.19-0.06
C
N O
Ph
SOO
Me
+0.20
-0.25-0.02
-0.16
-0.16
(O-transfer reagent)(N-transfer reagent)
Vidal J.; Damestoy S.; Guy L.; Hanachi J,; Aubry A.; Collet A. Chem. Eur J. 1997, 3, 1691-1709
N vs O Transfer: A suggested Model
O
N
R
R''
R'
smaller R'' groups
Nu"Nu-N"
N
O
R
R'
Nuδ+
δ−
δ−
R''
R, R'' = EWG
Nucleophilic Attack:Electronics Control
O
N
R
R''
R'
R" = bulky group
Nu
Nu"Nu-O"
O
N
R
R''
R'
Nuδ+
δ−
δ−
R, R', R'' = EWG
Nucleophilic Attack: Sterics Control
Vidal J.; Damestoy S.; Guy L.; Hanachi J,; Aubry A.; Collet A. Chem. Eur J. 1997, 3, 1691-1709
Outline
• Introduction• Heteroatom Transfer Reactions
N vs O Transfer: Mechanistic ConsiderationsO Transfer ReactionsN Transfer Reactions
• Photochemical Rearrangement Reactions• Conclusion
N-Sulfonyl (Davis) Oxaziridine
NO
SO
O
X
Y
N-Sulfonyl Oxaziridines (Davis Oxaziridines)
-Oxidation of Sulfides
NO Ph
SPhO
OPh2S Ph2SO
93 %
N O
OO NaHMDS-78 oC,THF
NO
S
PhO
OPh
N O
OO
OH
86 %, 98 % d.e.
-Hydroxylations of Enolates-Hydroxylation of Enolates
Davis, F. A.; Lal, S. G.; Durst, H. D. J. Org. Chem. 1988, 53, 5004.Evans, D. A.; Morrissay, M. M.; Dorow, R. L. J. Am. Chem. Soc. 1985, 107, 4346-4348
Davis Reagent: Epoxidation of Alkenes
60 oC
NO
S
PhNO2
O
OPh
PhPh
PhPh
O
3 h, 47 %
12 h, 95 %
Less Efficient than mCPBA
Davis, F. A.; Malik, N. F.; Award, S. B.; Harakal, M. E. Tetrahedron Lett. 1981, 917
Epoxidations with Oxaziridinium Salts
1
N
OCH3
BF4-
10 min, 84 %1h, 81 %
2h, 91 %10 h, 88 %
1h, 89 %3h, 92 %
1mCPBAAlkene
Ph Ph
C7H15
Ph
Ph
Ph
PhO
CO3H
Cl
NO
CH3
BF4-
CH2Cl2, 20 oC,
CH2Cl2, 20 oC,
0.5 h96 %
4 h95 %
O O
O86 %
no Bayer-Villiger product,O O
( )
1
Hanquet,G.; Lusinchi, X.; Milliet, P. Tetrahedron 1993, 22, 423-438Lusinchi, X.; Hanquet, G. Tetrahedron 1997, 53, 13727-13738
Epoxidation with Oxaziridinium Salts: Directing Effects
OO
HO
R
O
H
Epoxidation with peracid
substarate yield cis/trans selectivity
oxaziridinium salt mCPBA
OH
OH
85
95
60 / 40 92 / 8
60 / 40 95 / 5
OON
O
Epoxidation with oxaziridinium salt
δ+δ−
OAc
OAc
92
95
95 / 5 50 / 50
95 / 5 40 / 60
Lusinchi, X.; Hanquet, G. Tetrahedron 1997, 53, 13727-13738
The first Chiral Oxaziridinium Salt
H2N Ph
Me OH
NH
MePhOH
NH
MePh
N
MePh
N
MePh
BF4-
N
MePh
BF4-
O
1) MgSO4/CH2Cl22) NaBH4/EtOH
CF3COOH/ H2SO4
1) NaOCl2) NaOMe
Me3O+BF4-/
MeOHmCPBA/ CH2Cl2
20oC
single diastereomer23 % overall yield
Preparation
O
Ph
Ph
Ph
Ph
Ph
Ph
Ph O
Ph O
PhO
Ph O 63 %42 % ee
50 %23 % ee
10 %12 % ee
65 %5 % ee
Epoxidation reactions (Stoichiometric)
Bohe, L.; Hanquet, G.; Lusinchi, M.; Lusinchi, X. Tetrahedron Lett. 1993, 34, 7271-7274 Bohe, L.; Lusinchi, M.; Lusinchi, X. Tetrahedron 1999, 55, 141-154
Catalytic Asymmetric Epoxidation using a ChiralIminium Salt
Ph
Ph Ph
Ph O
0.05 eq 1, 2 eq KHSO5, 4 eq NaHCO3
MeCN / H2O (3%), ~10 h, rt
Ph
Ph O
Ph
Ph
KHSO5
KHSO4
N
MePh
BF4-
N
MePh
BF4-O
35 % e.e. 1
Bohe, L.; Lusinchi, M.; Lusinchi, X. Tetrahedron 1999, 55, 141-154
Iminium Salts with “Exocyclic Chirality”
Preparation:
O O
Br
Br2, CCl4
1 h
HBr (conc.)
10 min, 65 %
Br
O
R*NH2, NaBPh4,EtOH/MeCN2 h, 0oC to rt
N
BPh4-
70 %
1
Ph
Ph
PhPh
PhPh
Alkenecat..load. (mol %) yield (%) ee (%)
majorenantiomer
0.55
5
510
5
6868
73
7875
72
2740
63
6873
15
(R,R)(R,R)
(S,S)
(R,R)(R,R)
(R,R)
RR''
R'
RR''
R'
O
Oxone, Na2CO3,CH3CN, H2O, 0oC
Epoxidation Reactions:
1
Page, P. B.; Rassias, G.; Bethel, D. Schilling, M. B. J. Org.Chem. 1998, 63, 2774-2777
Stereocontrol of Oxaziridination is a possible problem
N RO
*
N R *
X-
N R *
OOSO3-
N R *
OOSO3-
N R *O
- SO42-
- SO42-
KHSO5
R3 R2
R1R3 R2
R1O
R3 R2
R1
R3 R2
R1OR3 R2
R1
O R3 R2
R1O
Page, P. B.; Rassias, G.; Barros, D. Ardakani, A.; Slawin A. J. Org. Chem. 2001, 66, 6926-6931
Can Functionalized Iminium Salts Solve the Problem of Stereocontrol ?
N
O
O
Ph
BPh4-
N OPh
OO
N
OO
N
OO
N
O
O
major
minor
O
ring flip
( a )
( b )
A B(X-Ray
Supported)
Page, P. B.; Rassias, G.; Barros, D. Ardakani, A.; Slawin A. J. Org. Chem. 2001, 66, 6926-6931
Catalytic Asymmetric Epoxidation Using a Functionalized Iminium Salt
64%, 20% ee (R)68%, 8% ee (R)
64%, 49% ee (1S,2R)73%, 20% ee (1S,2R)
52%, 17% ee (1S,2R)34%, 3% ee (1S,2R)
54%, 59% ee (S)43%, 5% ee (S)
52%, 52% ee (1S,2S)72%, 15% ee (R,R)
Catalyst 2Catalyst 1Epoxide
Me
PhO
OPh
Me
Ph
OPh
Ph
Ph
O
OPh
N
BPh4-
1
N
O
O
Ph
BPh4-
2
(Conditions: Oxone (2eq), Na2CO3 (4eq), H2O/MeCN (1:1), 0oC, 5 mol% catalyst)
Page, P. B.; Rassias, G.; Barros, D. Ardakani, A.; Slawin A. J. Org. Chem. 2001, 66, 6926-6931
Intramolecular Epoxidation of UnsaturatedOxaziridines
R1 R3
Nn
BnO
1. MeOTf, CH2Cl2, 0oC
R1
R2
R3
On
O2. aq. NaHCO3
R2
39%1HHnBu
41%2MeMeH
39%1MeMeH
Yield nR3R2R1
O O
OHmCPBACH2Cl2 OH
O
1. BnNH2, CH2Cl22. Oxone, NaHCO3, CH3CN / H2O
1. MeOTf, CH2Cl22. Aq. NaHCO3
NO
Bn
O
47 % 48 %
Regioselectivity can be complementaryto that of mCPBA
Armstrong, A.; Draffan, A. G. J. Chem. Soc., Perkin Trans. I 2001, 2861-2873
Stereoselective Intramolecular Epoxidation in Unsaturated Oxaziridines
O
nPrO
NPh
nPrO
1. MeOTf, CH2Cl2, 0oC2. Aq. NaHCO3
H
90 % de93 % ee
O H
OnPr
Ph
nPr
NO
1. MeOTf, CH2Cl2, 0oC2. Aq. NaHCO3
H
90 % de92 % ee
Armstrong, A.; Draffan, A. G. J. Chem. Soc., Perkin Trans. I 2001, 2861-2873
1
Epoxidations with Perfluorinated
Oxaziridines
NO
Fn-C4F9
C3F7N(C4F9)3
10 mol % SbF5
24h, 120 oC85 %
NC4F9F
C3F7 mCPBA
68 %
Preparation:Preparation:
O86 %
OAcO
OAc
85 %
CFCl3/CHCl3
CFCl3/CHCl3
CFCl3/CHCl3
-40oC 4 min
-40oC 4 min
-40oC 4 min
Epoxidation reactions :
OAc OAcO
88 %
2
3
4
Epoxidation reactions:
1
Arnone, A.; Marteau, D.; Novo, B.; Petrov, V.; Pregnolato, M.; Resnati, G.; J.Org. Chem. 1996, 61, 8805
Epoxidations of Electron Poor Olefins
F F
F X
F F
F XO
NO
F
n-C4F9
n-C3F7
1N
O
F
n-C5F11
n-C6F13
2
X Oxaziridine Conditons Yield(CH3)3Si neat / rt / 20 min 82 %
neat / 100oC / 16 h 60 %21Cl
Arnone, A.; Marteau, D.; Novo, B.; Petrov, V.; Pregnolato, M.; Resnati, G.; J.Org. Chem. 1996, 61, 8805
Oxyfunctionalization of Unactivated C-H Bonds by Perfluorinated Oxaziridines
• Enantiospecific• 3o C-H > 2o C-H > 1o C-H• Equatorial C-H > Axial C-H• Oxenoid Atom Insertion (?)
H
H
H
H
H
H
H
HHO
H
H
H
H
70 %
NO
C4F9 FC3F7
CFCl3,rt
H
BrCl
N
O
n-C4F9 F
n-C3F7
BrCl
OH
CF3Cl, rt, 30 he.e = 96 %e.e = 99%
Resnati, G.; Arnone, A.; Cavicchioli, M.; J. Org. Chem. 1994, 59, 5511-5513Arnone, A.; Foletto, S.;Metrangolo, P.; Pregnolato, M. Resnati, G. J.Org. Chem. 1999, 1, 281-284
Summary for O-Transfer Reactions
Oxaziridinium Salts:
•Very reactive for epoxidation of alkenes.•Syn selectivity for epoxidation of allylic acetates.•Capabe for catalytic asymmetric epoxidation.
Perfluorinated Oxaziridines :
• Very reactive O-donors.•Epoxidation of e- poor alkenesefficient.•Capable for C-H activation.
N
O
F
n-C4F9
n-C3F7
N
OCH3
BF4-
Outline
• Introduction• HeteroatomTransfer Reactions
N vs O Transfer: Mechanistic ConsiderationsO Transfer Reactions N Transfer Reactions
• Photocemical Rearrangement Reactions• Conclusion
Amination of Ammonia:A large Scale Industrial Process
NH2Cl OH-O O NH
NN HN NH
NH3
The First Stable N-Transfer Oxaziridines: N-N Bond Formation
NHR1
R2 Ar
PGN
ON
R1
R2NH
PGArCHO O
N
O
OtBu
NC
ON
O
OMe
58 %76%PG = Moc, 91 %PG = Boc, 92%
O N NHPG
NN NH
Moc
N CONH2
HNMoc
Ph
OH
NN
PG
H
PG = Moc, 77%PG = Boc, 70%
Ph
OH
NNH
Moc
76 %
H2NCOOH
HNNH
Moc
85 %
HO HNNH
COOH
Moc
67 %
Vidal J.; Damestoy S.; Guy L.; Hanachi J,; Aubry A.; Collet A. Chem. Eur J. 1997, 3, 1691-1709Vidal, J.; Guy, L.; Sterin, S.; Collet, A. J. Org. Chem. 1993, 58, 4791-4793
A More Powerful Reagent For Electrophilic Amination
Cl3CCHON
CCl3
Boc Oxone,K2CO3
H2O / CHCl3
Cl3C
Boc
86%
NO
PPh3 NBoc
O NCDCl3, 20 oC
quantitative
not detected
Cl3CNO
Boc
NO
Moc
O N NHBoc
O N NHMoc
Vidal, J; Hannachi, J. C.; Hourdin, G.; Mulatier, J. C.; Collet, A. Tetrahedron Lett. 1998, 39, 8845-8848
O-Amination of Alcohols: Synthesis ofHydroxylamines
OH1) LiHMDS, -78oC, THF
2 )O
NHBoc
> 95 %N
O
Boc
Cl3C
ONHBoc
80 %
O
NHBoc
85 %
O
NHBoc
50 %
ONHBoc
96 %
ONHBoc
80 %
MeO
ONHBoc
87 %
O
ONHBoc
80 %
Foot, O. F.; Knight, W. Chem. Comm. 2000, 975-976
O-Amination of Alcohols: One-pot Preparation ofOximes
ONH2
86 %
ONH2
70 %
ONH2
10 %
O
N
ON
51 %
78 %
O
HO
NO
56 %
NH m-CPBA
CH2Cl2, 0oC, 1h 49 %
HN O
R OH1) KH, DMPU, 0oC
2)R ONH2
O
O
HAcOH, rt,10 min
H
RON
HN O
Choong, I. C.; Ellman, J. A. J. Org. Chem. 1999, 64, 6528-6529
S-Amination : O-Transfer is a Problem
Ph
MocNH
< 15 min
S SNMoc
SO
O
Solvent T (oC) Amination/Oxidation
CDCl3
CDCl3
CDCl3
CH3CN
CH3CN
CH3CN
19
0
-34
19
0
-35
34 / 66
45 / 55
52 / 48
48 / 52
58 / 42
67 / 33
Vidal J.; Damestoy S.; Guy L.; Hanachi J,; Aubry A.; Collet A. Chem. Eur J. 1997, 3, 1691-1709
Improved Control of N vs O Transfer to S-Nucleophiles
SN
O
NEt2SO
S Cl
NO
O
NEt2
>10/1-40CF3CH2OH
10/119CF3CH2OH
7/1-30MeOH
3/119MeOH
2/3-40THF
1/419THF
1/3-40Toluene
<1/1019Toluene
N/OTemp. oC Solvent
Ar
ON
COOR
O N
Ph
COORvsPh S
Me
PhSMe
δ−
δ+ δ−
δ+
(more polar TS)
Armstrong, A.; Edmonds, I. D.; Swarbrick, M. E. Tetrahedron Lett. 2003, 44, 5335-5338
High Degree of N-Transfer with a Novel Oxaziridine
1. BocN=PPh3, THF
2. mCPBA, BuLi CH2Cl2
50 %
EtOOC COOEt
O
EtOOC COOEt
O NBoc
>98/2-40CDCl3
95/50CDCl3
90/1010CDCl3
N/OT (oC)Solvent
S SNMoc
SO
EtOOC COOEt
O NBoc
EtOOC COOEt
N BocO
Nu
H
N BocO
Nu
NC
(less favored)
Transition States for Byproduct’s Formation:
Armstrong, A.; Cooke, R. S. Chem. Comm. 2002, 904-905
Tandem Amination of Sulfides / [2,3]-sigmatropic rearrangement
SPh R1
R2
NBocR1
R2
PhSEtOOC COOEt
1.05 eq
O NHBoc
CH2Cl2-40 oC
R1
SX
R2
R2
BocNS X
R1
EtOOC COOEt1.05 eq
O NHBoc
CH2Cl2-40 to rt 1h
13MeMeN-hexyl
88PhHPh
66COOtBuHPh
85IHPh
Yield (%)R2R1X
85COOMeH
73PhH
93MeMe
94MeH
Yield (%)R2R1
Armstrong, A.; Cooke, R. S. Chem. Comm. 2002, 904-905
Armstrong, A.; Cooke, R. S.; Shanahan, S. E. Org. Biomol. Chem. 2003, 1, 3142-3143
C-Amination of Enolates with N-HOxaziridines
HN NH
O
O O
HN NH
O
O ONH2
HN NH
S
O O
HN NH
S
O ONH2
78 %
82 %
HN NBn
OO
O O
OO
O O
OON
N NBn
HONH2
O90 %
79 %
ONH
aq. NaOH
aq. NaOH
aq. NaOH
aq. NaOH
Andreae, S.; Schmitz, E. Synthesis 1991, 327-341
Amination of Enolates: Aldol Addition is Competing
NO
NC
Boc
OLI
Ph
O
PhNHBoc
OLi
BuO
O
BuONHBoc
O N
OLi
Ph
O
O N
O
Ph
O
NHBoc
35 %
33 %
38 %
O
Ph
major problem: aldol addition
O
BuO
OH
CN
O N
O
Ph
O
HO
CN
HO
CN
“significant amounts”
Vidal, J.; Guy, L.; Sterin, S.; Collet, A. J. Org. Chem. 1993, 58, 4791-4793
Can ortho-substituted Oxaziridines Slow Down the Aldol Addition ?
O
X H2N
O
NEt2
p-TsOH (cat)
PhMe, heat
N
X
O
NEt2mCPBA, nBuLi
CH2Cl2,-78 to rt
N
X
O
NEt2O
> 92 % trans
7552-CN
10314-Cl
--2,6-diCl
--2-Cl
2039 4-CN
21X
ButO
O 1. LDA, THF
2. oxaziridine
ON
O
NEt2H
tBuO
O
tBuO
OH
X1 2
Armstrong, A.; Atkin, M. A.; Swallow, S. Tetrahedron Lett. 2000, 41, 2247-2251
Asymmetric Amination of Carbanions
R CN1. LHMDS, THF, -78oC
2. oxaziridine NNH2
N
0NH2
R
(R) (S)O
R
OHN
23577CN
33484 1-naphthyl
523192-naphthyl
50555Ph
de (%)Yield (%)Time (h)R
Page, P. B.; Limousin, C.; Murrell, V. L. J. Org. Chem. 2002, 67, 7787-7796
Summary for N-Transfer
ON
O
OtBu
NC
Cl3C
BocN
OO NH HN O
N-Amination,O-Amination
Unstable N-Amination O-Amination
NO
O
NEt2
Cl
COOEtEtOOC
O NBoc
S-AminationS-Amination
NO
O
NEt2
CNO
HN
Enolate Amination Carbanion Amination
Outline
• Introduction• Heteroatom Transfer Reactions
N vs O Transfer: Mechanistic ConsiderationsO Transfer Reactions N Transfer Reactions
• Photochemical Rearrangement Reactions• Conclusion
Photochemical Rearrangements:General Pattern
R ON
R'R
hν RN
R'R
O Alkyl migrationN
O
R R'
R
Photochemical Rearrangement ofOxaziridines: Puzzling selectivity !
NROMe hv N
Me
O RN
O
Me
R
95 5
NR
MeO N
R
MeO
NR
MeO
( less stable radical predominates )
( b )( a )
:
NO
Me
hvMe
O
N not objerved : N
O
Me
(more strained product predominates)
b)
2)
1)
Oliveros, E.; Riviere, M.; Lattes, A. Nouv. J. Chim. 1979, 3, 739-753
Rarello, J.; Riviere, M.; Desherces, E.; Lattes, A. C. R. Hebd. Seances Acad. Sci., Ser. C 1971, 273, 1097-1100
Theoretical Studies Gave the Answer
Stepwise mechanism:a) Photochemical breaking of the N-O bondb) H (or R) migration to N
NO
HHAHS
A
NO
HSHA H
NO
HS HAH
NO
HSHHA N
O
HS
H
HA
NO
HA
H
HS
TSS
TSA
E
- 5 kcal/mol0 kcal/mol
19.8 kcal/molTSS
TSA
A
The bond anti to the N-lone pair is cleaved more easily
Oliveros, E.; Riviere, M.; Malrieu, J. P.; Teichteil, C J. Am. Chem. Soc. 1979, 101, 318-322
Basic Concepts that can be Exploited
NO
R'
hvR NR
OR'
a)
Migration of less substituted group
Asymmetric Ring Expansion
N Ph
Me
O
tBu
hv NO
tBu
Ph
Me
NO
tBu
PhMe
13 : 1
b)
Lattes, A.; Oliveros, E. J. Am. Chem. Soc. 1982, 104, 3929-3934
Applications of Photochemical rearrangement of Oxaziridines
N O
Me R
Ph Ph
OBnO2C N
O hv
benzene
N O
Me R
Ph Ph
OBnO2C N
O
H
H
N
H
O
N
O
48 %
hv (rarely synthesized bicyclic skeleton)
NN
OCOOCH3
H HH
hv, CH3CN
68 % N
COOCH3
HNH H
O N
COOCH3
HNH H
H
(+)-Alloyohimbane(d.r. = 2.2 : 1)
Wenglowsky, S.; Hegedus, L. J. Am. Chem. Soc. 1998, 120, 12468-12473Bourguet. E.; Baneres, J. L.; Girard, J. P.; Parello, J.; Vidal, J. P.; Lusinchi, S.; Declercq, J. P. Org. Lett. 2001, 3, 3067-3070
Aube, J.; Ghosh, S.; Tanol, M. J. Am. Chem. Soc. 1994, 116, 9009-9018
ConclusionsOxaziridines show a diversity in reactivity
that can be very useful in Organic Synthesis:
•Oxaziridinium salts are systems that can be furtherdevelopped in catalytic asymmetric epoxidations.
•Perfluorinated oxaziridines’ reactivity should be explored more, especially in C-H activation reactions.
•N-transfer oxaziridines are very useful for electrophilic amination processes.
•Oxaziridines’ photochemical rearrangement is a valuable method for lactam synthesis.
Thanks-Giving To:
Proffesor W. D. Wulff
Wulff’s Group:
ThaliaKyoungsoo ChrysoulaSoong-hyun
ManishVijayYuZhenjieGangDingKeith
LianJieGlennVictorCoryChunruiReddyYongheng