click reaction and its catalytic activity

N

O

TEMPO

Immobilized TEMPOs – Literature

NH

N OSilicaSi O N O

O

OON OLINKER

= MeOPEG

NN

NO

N

N

C8F17

C8F17

C8F17

C8F17

N O

Bolm, 1999

Silica-supported TEMPO Poly(ethylene glycol)-TEMPO

Pozzi et al, 2003

Pozzi et al, 2005

COORCOO

NOH

R = TEMPOR = HR = Me

Tanyeli, 2003

Polynorbornene-derived TEMPOFluorous tagged TEMPO

D.Burnel et al, 2001

MCM-41 supported TEMPO

A strategy for ligation of TEMPO to polymer2,3

entry alcohol catalystb yieldc

1

2

3

4

5

6

7

8

4-Bromobenzyl alcohol

4-Methylbenzyl alcohol

1-Octanol

1-Decanol

Cyclohexanol

Benzylalcohol

2-Phenylethanol

1-Dodecanol

1,2,3,4

1,2,3,4

1,2,3,4

1,2,3,4

1,2,3,4

1,2

1,2

1,2

all >93

all >98

all >86 all >93 all >93

all >99

all >92

all >96

Oxidation of alcohols under molecular oxygen conditiona,4

a Alcohol (1 mmol) in CH2Cl2 (2 mL), KBr (0.3 mmol), NaOCl (1.3 mmol), NaHCO3 (0.2 mmol), b 1 mol% of catalyst 2, 3, 4 and 2.5 mol% of 1 used, c Isolated yields.

entry alcohol catalyst yieldb

1

2

3

4

5

6

7

8

Benzyl alcohol

4-bromobenzyl alcohol

4-methylbenzyl alcohol

1-octanol

Cinnamyl alcohol

1-decanol

4-methoxybenzyl alcohol

Cyclohexanol

1,4

1,4

1,4

1,4

1,4

1

4

4

98,89

95,92

98,98

97,82

96,90

96

96

93

We have developed an extremely simple and practical protocol for grafting TEMPO into polystyrene and fluorous tag via click reaction

Proved highly efficient for the chemoselective oxidation of alcohols under bleach as well as molecular oxygen condition

Catalyst was recovered and recycled efficiently without loss of catalytic activity

CO2Et

OHHO

R

CO2Et

OO

ROO

R

OH

Acetone, 24h

CH2Br

83%

OO

R

Cl

CuI, DIPEA

C8F17N3

87%

CCl4, PPh3

56%

,

O

R

ONN N N

NN

C8F17

N3

NaN3DMSO

49%

K2CO3, 18-crown-6 LiAlH4

THF, 81% THF, 48h THF, rt, 24h

60 oC, 24h O

R

ONN N N

NN

C8F17

C8F17

C8F17N

NN

O

NO

CuI, DIPEA

86%

THF, rt, 24h

N

O

O

O

R

ONN N N

NN

C8F17

Cl

C8F17

R = HR = OH

R = HR = OCH2C CH

R = HR =OCH2(Triazole)CH2CH2C8F17

R = HR =OCH2(Triazole)CH2CH2C8F17

R = H (3)R =OCH2(Triazole)CH2CH2C8F17 (4)

R = HR = OCH2C CH

R = HR = OCH2C CH

Introduction

2,2,6,6-Tetramethylpiperidine(TEMPO)1 is generally characterized as a mild oxidants, more interestingly it is used in catalytic version in the oxidation of alcohols in presence of sodium hypochlorite and KBr which displaces the traditional use of stoichiometric oxidants such as chromium reagents.

Immobilization of TEMPO on multiple fluorous tag

Conclusion

References

Expedient Immobilization of TEMPO on Fluorous Tag and Polystyrene via Click Reaction and Its Catalytic Activity

Tamilselvi Chinnusamy, Alexanderu Gheorghe, Erick Cuevas Yañez, Oliver Reiser*

Institute of Organic Chemistry, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany

Oxidation of alcohols under bleach conditiona,2,3

Labelev,Kazarnowskii,19601

entry catalyst alcohol cycle yield

1

2

3

1

2

4




1-4

1-4

1-4

all >93

all >90

all >93

N

O OH

N

OH

R1 R2

OH

R1 R2

O

OBrBr

OCl Cl

entry catalyst alcohol cycle yield

1

2

1

4



1-4

1-4

all >91

71-99

a Alcohol (1.0 mmol) in AcOH (1mL), Mn(NO3)2.4H2O (2.0 mol%), Co(NO3)2.6H2O (2.0 mol%), catalyst 1 (2.5 mol %)/4 (1.0mol%) and at oxygen atmosphere. b Isolated yields.

R1 R2

OH TEMPO (1mol%)

CH2Cl2 R1 R2

O

Oxiadation of alcohols into carbonyl compounds using TEMPO

• Lebelev, O. L.; Kazarnovskii, S. N. Zhur. Obshch. Khim. 1960, 30, 1631.• Gheorghe, A, Matsuno, A.; Reiser, O. Adv.Synth.Catal. 2006, 348, 1026.• Gheorghe, A.; Cuevas-Yañez, E.; Horn, j.; Bannwarth, W.; Narsaiah, B.; Reiser, O. Synlett 2006, 2767.• Cecchetto, A.; Fontana, F.; Minisci, K.; Recupero, F. Tetrahedron Lett. 2001, 136, 1591.

TEMPO-catalyzed bleach-oxidation of alcohols using bromide as co-catalyst

N

O

O

N

O

OH

Br

NaH, DMF

N

O

ON

NN

N3 CuI (6 mol%)

THF

N

O

ON

NN

C8F17

N3C8F17

CuI (6 mol%)

THF, 80 %

78 %

4.3 mmol/g

1 2

N

O

NN

N N

N

O

N(CH2)6

NH(ter t-octyl)5

PIPOSheldon et al. 2001

25 mg F17-Click-TEMPO in 10 mL DCM

Addition of 1g of silica gel 60 after 1 min; complete retention

O ON

NN

NN

NO

NN N

C8F17

C8F17C8F17

N

O

N

O

NNhydrophilic

hydrophobic

O ON

NN

Ph

NN

N

Ph

O

NN N

Ph

N

O

N

O

NN

Activity comparison of 1,4 and TEMPO catalysts in the Anelli oxidation of 4-methylbenzylalcohola

>750

1200

>750

116

450

>400

>750

1480

>750

500

300

300

29

300

100

500

370

500

>98

60

>98

68

58

>98

97

74

96

40

15

40

15

40

15

40

15

40

TEMPO (0.2)

TEMPO (0.2)

2 (0.2)

1 (2.5)

1 (0.2)

4 (1.0)

4 (0.2)

4 (0.2)

5 (1.0)

1

2

3

4

5

6

7

8

9

TOF (h-1)TONyieldb

(%)time

(min)

catalyst

(mol%)entry

a Alcohol (25 mmol,1.0 equiv.) in CH2Cl2 (50 mL), KBr (0.2 equiv.), NaOCl (1.1 equiv., 20 mL), NaHCO3 (0.5 equiv.), b Isolated yields, purity 98% in all cases.

Figure 1

Figure 2

Figure 3No affinity to fluorous silica

Excellent retention on silica 60

Activity comparison of 1, 4 and

TEMPO catalysts in the Minisci condition

Decantation of DCM followed by

addition of 10 mL of EtOAc to the

silica; >90% F17-Click-TEMPO

extracted in EtOAc

Solubility:

9 mg @ 50 mL CH2Cl2

Solubility:

>100 mg @ 50 mL CH2Cl2

95

26

84

TEMPO

1

4

1

2

3

yieldcatalystentry

OH HO

Catalyst (1mol%)

Mn(II),Co(II)O2, AcOH

= Polystyrene

Figure 4

Figure 5

click reaction and its catalytic activity

Documents