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The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张张张 1

The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

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Page 1: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry

2010.12.04

张文全

1

Page 2: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

introduction

Alkaline earth metals are very attractive because they are abundant and ubiquitous elements in nature and form safe compounds compared with other heavy transition metals. However, their positive use as catalysts in asymmetric synthesis is still limited. Their strong Brønsted basicity and mild Lewis acidity can influence their catalytic activity, as well as chiral modification of a complex in a positive manner.

2

Page 3: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

calciumThe application of calcium complex in organic chemistry will showfollow

Baylis¨CHillman

Baylis¨CHillman

Mannich reaction

Friedel-Craft reaction

Hydroarylation of Alkenes

Hydroamination

Pictet-Spengler reaction

Tischenko ReactionHydrophosphination

Aldol Reaction

CaLn

Michael Reactions

3

Page 4: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

O

PhCHO

1eq 1.5eq

CaL(16mol%)Bu3P(10mol%)

THF,rt, 7h

O

Ph

OH

O

O

Ca

First example of an optically active calcium catalyst

Shiro Ikegami, Tetrahedron Letters 41 (2000) 2165

Baylis–Hillman Reaction

62 yield%56 ee%

4

Page 5: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ph

O

Ph

H3CO

O

OCH3

O Ph

O

Ph

CH(CO2Me)2

*

cat. 15mol%

toluene, -15oC24h

2eq KOH

1eqCaCl2absEtOH

2KClOH

OH

O

OCa

H3CO

O

OCH3

Ocat. 15mol%

toluene, -15oC24h

O

O

CH(CO2Me)2

75 yield%88 ee%

G. Kumaraswamy, Tetrahedron Letters 42 (2001) 8515

Michael Reactions

5

Page 6: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

OO

OMe

O 10mol%(R)cat

toluene,-40oC 12h

O

CO2Me

O

*

OH

OH

*2eq KOH

1eqCaCl2absEtOH

O

O

* Ca 2KCl

R2

R2 R1

R1

OH

OH

R3

R3

OH

OH

OH

OH

OO

OMe

O 10mol%(R)cat

toluene,-40oC 12h

O

CO2Me

O

*88yield%80ee%

G. Kumaraswamy, Adv. Synth. Catal. 2005, 347, 867 6

Page 7: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R1O

O

OR1

O

R2 NO2

Ca(OAr)2(10mol%)ligand(10mol%)

toluene,-20oC24h, 0.2M,4AMS

R1O

O

OR1

O

R2

NO2

N

O

N

O

NH HN

PhPh

O2S SO2NO

N N

O

R1

R2R2

R1

NO

N N

O

Ph

PhPh

Ph

anti

Ca(OAr)2

Ar=p-MeOC6H4

18-96ee%50-quant yield%

NO

N N

O

Ph

PhPh

PhCaOAr ArO

Shu Kobayashi, Angew. Chem. Int. Ed. 2009, 48, 9117 7

Page 8: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

MeO

O

OMe

O

N

NN CaArO OAr

*

ArOHN

NN Ca

*

MeO

O

OMe

O

MeO

O

OMe

O

Ph

N+

O O-

OAr

N

N NCa

*

ArO

MeO

O

OMe

O

Ph

NO2

PhNO2

*

*

8

Page 9: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

upto 84ee%

NO

OR1

Ph

O

OR2

M(OiPr)2(10mol%)Pybox(10mol%)

Conditions, 34h, 0.2MMS 4A

N O

OR1

PhR2O

O

NO

N N

O

R1 R1

R2R2

R2R2

NO

N N

O

R1 R1

R2R2

R2R2

CaPrOi OiPr

Shu Kobayashi, Tetrahedron: Asymmetry 21 (2010) 1221

9

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10

Page 11: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

N

O

O

O

R

O

R1O OR1

O

OMe OH 10mol%

Ca(OR2)2(10mol%)PyBox(11mol%)

N

O

O

O

R

R1O

O

R1O O

almost>90ee%

NO

N N

O

Ph Ph

ligand

NO

N N

O

Ph PhCa

EtO OAr

real catalyst

Shu Kobayashi, J. AM. CHEM. SOC. 2010, 132, 789011

Page 12: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R1

R2

O

Ph N

Ph

OR3

Oligand(10mol%)Ca(Oi-Pr)2(10mol%)

-30oC,THF,0.2M,12hMS 4A

Ph N

Ph

OR3

O

R1

R2O

78-99ee%

with excellent diastereo- and enantioselectivities

R2

O

Ph N

Ph

OR3

Oligand(10mol%)Ca(Oi-Pr)2(10mol%)

-30oC,THF,0.2M,12hMS 4A N

HPh

Ph

OR2O

O

OR3

R2

O

Ph N

Ph

NR1R3

Oligand(10mol%)Ca(Oi-Pr)2(10mol%)

-30oC,THF,0.2M,12hMS 4A N

HPh

Ph

OR2O

O

NR1R3

N

O

N

O

Ph Phligand

Shu Kobayashi, J. AM. CHEM. SOC. 2007, 129, 5364Shu Kobayashi, J. AM. CHEM. SOC. 2008, 130, 13321Shu Kobayashi, O.L. 2008, Vol. 10, No. 5, 807

with excellent diastereo- and enantioselectivities

12

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Catalytic cycle of the 1,4-addition reaction

13

Page 14: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Two Possible Reaction Mechanisms of the [3 + 2] Cycloaddition Reaction

14

Page 15: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

O

OR2

O

R2Oconcerted pathway

Ph NOR1

O

NH

Ph

OR2O

O

OR1

O

OR2

trans

O

OR2 concerted pathway

Ph NOR1

O

NH

Ph

OR2O

O

OR1

O

OR2

cisO

OR2

NH

Ph

OR2O

O

OR1

O

OR2

trans

NH

Ph

OR2O

O

OR1

O

OR2

cis

so stepwise is possible

cis/trans=2/1

15

Page 16: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R1

Ar

R1

Ar

Ar

R1

R2

R1

OH

R1

OH

OH

R1

R2

ArH

R1

OHR2

R1

OHR2

OH

R1

R2

R2

R1

Ar

R1

Ar

Ar

R1

R2

R2

R2

R2

secondary tertiary

5mol% Ca(NTf2)2/Bu4NPF6 room temperature

Ca(NTf2)2+Bu4NPF6 CaNTf2PF6

more reactive

Meike Niggemann, Angew. Chem. Int. Ed. 2010, 49, 3684

Friedel-Craft Reaction

electrion-rich AromaticArH =

CaNN

F3CO2S

SO2CF3

SO2CF3

F3CO2S

16

Page 17: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

HO

CaL

NuO O

ArH=H

17

Page 18: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ar H

NBoc

R1

O

R2

O

R3cat(2-5mol%)

Ar

NH O

R1

O R3

R2

Boc

solvent

cat:

Kazuaki Ishihara, Angew. Chem. Int. Ed. 2010, 49, 3823

Mannich Reaction

18

Page 19: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ar H

NBoc

R1

O

R2

O

R3cat(2-5mol%)

Ar

NH O

R1

O R3

R2

Boc

solvent

when R2=H, H(1b) is betterwhen R2=H and R1 or R3 =SR, Ca(1a)2 is better

19

Page 20: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

N

HR1

Boc

R2O OR2

O O

Ca(OiPr)2

PyBox Ligand HN

R1

Boc

CO2R2

CO2R2

up to 77%ee

N

O

N

O

NO

N N

O

R1 R1

OH

I

OH

I

NO

N N

O

Bn Bn

Aliphatic N-Boc imine can react, good yield but low ee

Shu Kobayashi, J. Org. Chem. 2010, 75, 963 20

Page 21: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ar1Ar2

Ocat.10mol%

tol. -10oC, MS4AtBuOOH,48h

Ar1Ar2

O

Oupto 91 yield%upto 80 ee%

O

O

* Ca

O

O

* CaO

O

O

Ar2Ar1

O

+HO

* CaO

O

tBuOOHAr1Ar2

O

O

Ar1Ar2

O

n

n

n

O

OCa

trime

ric

Ca

Ca

Ca

OO

O

O

O

O

* *

*

epoxidation

G. Kumaraswamy, Tetrahedron: Asymmetry 14 (2003) 379721

Page 22: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R1

R3 R4

R2Ar-H

Ca(NTf2)2/Bu4NPF6 r.t.

Ar

R1

R3

H

R3

R4

OH

OS

O

Arene electrion-rich Aromatic

R1

R3

R2etcolefinic

R1

R3

R2

CaNTf2PF6 R1

R3

R2CaPF6

Nu

path one:

Meike Niggemann, Chem. Eur. J. 2010, 16, 11246

path two:

Hydroarylation of Alkenes

HO

CaL

Nu

22

Page 23: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

KN(SiMe3)2 BDICH CaI2N N

Ar ArCa(Me3Si)2N THF

THF

N HNBDIH

HNLCa

n

H2N n

HN

n

HNLCa n

H2N nHN(SiMe3)2

N NAr ArCa

(Me3Si)2N THF

Michael S. Hill, J. AM. CHEM. SOC. 2005, 127, 2042

Hydroamination

23

Page 24: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

aminoalkene product Time(h) Temp.(oC) Conv.%

24

Page 25: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

N NAr ArCa

(Me3Si)2N THF

1

Ph

H2N

NPh10mol%cat3

C6D6,r.t.

Peter W. Roesky, Organometallics 2007, 26, 4392

25

Page 26: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

HO

R1

NH2

H R3

OHO

R1NH

R3

R1-H or OMe aldehydes

3AMS, DCM23oC

10mol%Ca[OCH(CF3)2]2

HO

R1

NH2

R2 R3

O cat. 20mol%HO

R1 NH

R2 R3

R1-H or OMe ketones

3AMS, tol.100oC

regioselective products in most cases, giving rise to only the A-ol isomer.However, when a nitrogen functionality is present, the isomeric ratio of products is altered to give mixtures of the favored 6-ol isomer and the disfavored B-ol regioisomer.

such as:

HO NH2HO

NH3AMS, tol.100oC

N

ON

NH

NOH

A-ol B-ol

10mol%Ca[OCH(CF3)2]2

Pictet-Spengler Reaction

26

Page 27: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

O

NN Ca

OROR

CaRO

NCa

ORN

OCa

RO

James P. Stambuli, ORGANIC LETTERS, 2008, Vol. 10, No. 22, 5289James P. Stambuli, J. Org. Chem. XXXX, XXX, 000

HO

R1

NH2

R2 R3

O cat. 20mol%HO

R1 NH

R2 R3

R1-H or OMe ketones

3AMS, tol.100oC

O

O

OMe

O

O

O

Ketone:

27

Page 28: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

HO

R1

NH2

HO

N

R1

HO

N

R1

CaOR

OR

HO

N

R1

Ca

ORH

-OR

HO

N

R1

Ca

OR

HO

NH

R1

R1CHO

Ca(OR)2

Ca(OR)2

ROH

28

Page 29: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R H

O 0.1-10mol%cat

C6D6, rt R O

O

R

NCa

NAr Ar

(Me3Si)2N THF

Ar=2,6-diisopropylphenyl

10-96yield%

O

O

CF3

O

OMe

O O

Anthony G. M. Barrett, Michael S. Hill, O. L. 2007, Vol. 9, No. 2, 331

Tischenko Reaction

CaL

O

O

R

R

R

O

H

How to start the catalic cycle?being continuing to study

29

Page 30: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

R HPPh210mol%cat

C6D6,25-75oC13-36h

RPPh2 78-95conv%

Anthony G. M. Barrett, Michael S. Hill, Organometallics 2007, 26, 2953

Hydrophosphination

30

Page 31: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Anthony G. M. Barrett, Michael S. Hill, Organometallics 2008, 27, 497

R1N C NR1 HP(R3)2catalyst

R1

NH

NR2

P(R3)2

C6D6, r.t.

31

Page 32: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ca[(H3C)3Si]2N

[(H3C)3Si]2N L

L

R

R

OH

OHL=THF, DME

R= H, OCH3

R

R

O

O

CaLn

O

H

O

R

O

R

OH

cat3mol%

CH3CN mix THF-20oC

O O

Ocat3mol%

CH3CN mix THF -20oC

O

R

OH

76 yield%91 ee%

Ryoji Noyorib, Tetrahedron Letters 42 (2001) 4669

Aldol Reaction

32

Page 33: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

NHAc

R1

R

N

N

CO2i-Pr

i-PrO2C

cat. 10mol%4A MS, -35oC

then HBr, EtOH

cat. 10mol%4A MS, -35oC

then NaBH4, MeOH

O

NNH

CO2i-Pr

R1

CO2i-Pr

Ree: 85-95%

NHAc

NNH

CO2i-Pr

R1

CO2i-Pr

Rdr: >95:5; ee: 88-96%

O

OP

O

OCa

n

Jieping Zhu, O. L. XXXX, Vol. xx, No. x 33

Page 34: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

strontium

HO

O

HO

ArAr

Z

O2S NH HN SO2

Ph Ph

Need to develop new ligand

34

Page 35: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ph

NHN

OiPr

O2S

Ar

catalyst(10mol%)

MS 4A, DMFRT, 17h

NBoc O2S

Ar

Me

OiPrPh

NBoc

N

OiPr

O2S

Ar

cat.DMF

N-

OiPr

O2S

Ar

+ML(dmf)m

THF

N

OiPr

O2S

Ar

ML(dmf)m

S. Kobayashi, Angew. Chem. Int. Ed. 2009, 48, 5927S. Kobayashi ,Bull. Chem. Soc. Jpn. Vol. 82, No. 9, 1083

Mannich Mg(OtBu)2

Sr(HMDS)2

35

Page 36: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

solvent effect

Conditions A: DMF, RT, 17 h, Ar=2,5-xylyl.Conditions B: Ligand 4 (11 mol%), THF, RT, 24 h, Ar=p-NO2-C6H4.

The addition of ligand 4 generally increased the syn selectivity

N

O O

N

ligand 4

36

Page 37: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

NHN

OiPr

O2S

Sr(OiPr)2 (10mol%)ligand (12mol%)Et3N(10mol%)

THF,MS 4A,20oC48h, 85%yieldsyn/anti 83:1757% ee(syn)

NBoc O2S

Me

OiPr

NBoc

NO2NO2

O2S NH HN SO2

Ph Ph

this is the first example of a catalytic asymmetric Mannich-type reaction of a sulfonylimidate

37

Page 38: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

EtO2C

EtO2C Ph Ph

OSr(OiPr)2(0.5-5mol%)Ligand(0.6-6mol%)

MS 4A(100mg)toluene,25oC,

EtO2C

CO2Et

Ph

Ph

O

O2S NH HN SO2

Ph Ph

Ligand:

Sr(O-i-Pr)2 ligand 2i-PrOHO2S N N SO2

Ph Ph

Sr

O2S N N SO2

Ph Ph

Sr

MeO

O

OMe

O

>90 yield%>90 ee%

Shuj Kobayashi, J. AM. CHEM. SOC. 2008, 130, 2430

Michael Reactions

38

Page 39: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

n-PrO2C

n-PrO2C

Sr(HMDS)2(5mol%)Ligand(6mol%)

MS 4Atoluene,25oC,

O

Ph

OPhn-PrO2C

n-PrO2C

donor acceptor

O2S NH HN SO2

Ph Ph

ligand

Shu Kobayashi, Chemistry Letters Vol.38, No.3 (2009)

39

Page 40: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ph

O

catalystTMSCN(2eq)2,6-dimethylphenol(2eq)

THF, 40oC Ph

O NC

HO

O

P

HO

O

PhPh

HO

O

HO

ArAr

ZAr= Ph, p-tolZ= OH, OMe, OiBu, H

Sr(OiPr)2 (0.5 mol%) + ligand (0.8 mol%)

HO

O

HO

p-tollot-p

BuOi 100yield%97ee%

Motomu Kanai, Masakatsu Shibasaki, J. AM. CHEM. SOC. 2010, 132, 886240

Page 41: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

41

Page 42: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

42

Page 43: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

barium

Barium has the largest ionic radius, which often form oligomerLike:

43

Page 44: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

44

OTMSCO2Me

MeO2C

Ba(OiPr)2 ligand

CH2Cl2

YCO2Me

Z

CO2Me

Y = OTMS (and OH), Z = HZ = OTMS (and OH), Y = H

HO

O

HO

ArAr

Z

F

F

64 yield%3:1 d.r88 ee%

additive CsF, the same mol% as Ba/ligand91 yield%4:1 d.r97 ee%

Motomu Kanai, Angew. Chem. 2009, 121, 1090

Diels–Alder-type reaction

Page 45: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

OTMS

45

Page 46: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

RCHOO

Ph

(R)-BaN-M(5mol%)

DME, -20oC R

OH

Ph

O

Ba(O-i-Pr)2OMe

OH

2.5 eq

DMErt

evap.

i-PrOH

DME (R)-BaB-M

MeO

O OMe

OBa

X

X

X = BINOL-Me or DME

Masakatsu Shibasaki, Tetrahedron Letters 39 (1998) 5561

Aldol Reaction First example of an optically active alkaline meta catalyst

up to 70 ee%

46

Page 47: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

MeO

O OMe

OHBa

X

O

R

HO

BaO

O

O

O

X

X* *

BaO

O

O

OX

* *

O

R

HRCHO

R

OH

Ph

O

O

Ph

X

X

catalytic cycle

47

Page 48: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

Ba(OtBu)2O

HOphenol good yield and dr value

RCHON

Boc

OBa alkoxide (10 mol%) phenol (22mol%)

NH

O

R

OBoc

0oC, THF, 0.2M, 24h

O

Shu Kobayashi, J. AM. CHEM. SOC. 2006, 128, 8704 48

Page 49: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

O

HR

O

OBn

Ba(O-iPr)2 (5-10 mol%) ligand (5-10mol%)

DME

O

OBnR

OH

y-adduct

upto 99 ee%

Masakatsu Shibasaki, J. AM. CHEM. SOC. 2009, 131, 10842

49

Page 50: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

N

HR

PPh2

O

N

Boc

O

R'

O Ba(O-t-Bu)2(10mol%)ligand(22mol%)

0oC, DMF, 0.2M, 48h MS 5A

N

H

OO

R'

R

NPh2P Boc

O

O

HOligand

Shu Kobayashi, Chem. Commun., 2007, 1236

Mannich reaction

50

Page 51: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

NPPh2

R H

OO

OBn

Ba(OAr)2(0.5-10 mol%)

THF, 0oCAr= 4-MeO-C6H4

or chiral ligand

O

OBn

NH

R

Ph2P

O

53-88% yieldup to 80% ee

Masakatsu Shibasaki, O. L. 2007, Vol. 9, No. 17, 3387

OH

OH

O

O

chiral ligand

51

Page 52: The application of alkaline metal(Ca, Sr, Ba) complex as catalyst in organic chemistry 2010.12.04 张文全 1

HN

R R1

O

R2

Ba(HMDS)2 (10mol%) ligand(10mol%)

tBuOMe/THF=9/1 rt, 24h 0.05M, MS 4A

HN

R

R1R2

O

SiPh3

SiPh3

OH

OH

Kobayashi, Chem.sAsian J. 2010, 5, 1974

Friedel-Crafts-type Reaction

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conclusion

1. The Alkaline earth metals can be used in Many important reactions. But some of the mechanisms are unclear, still.

Their positive use as catalysts in asymmetric synthesis is limited, also.

2. Their strong Bronsted basicity and mild Lewis acidity can influence their catalytic activity, as well as chiral modification of a complex in a positive manner. So synthesis of new ligands need to be considered.

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Thank you for your attention!

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