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R Pd X + RM

(M = Si, etc.)

III.2.4 Overview of Other

Palladium-Catalyzed Cross-Coupling

Protocols

TAMEJIRO HIYAMA and EIJI SHIRAKAWA

'

A. INTRODUCTION

In this section is reviewed the cross-coupling reaction of organometallic compounds containing a main group metal such as Si, Ge, Cd, In, Hg, Pb, or Bi, not covered in Sects. III.2.1III.2.3. The carbon–metal bond of these compounds, although less polarized than those of the organometallics covered in preceding sections, has sufficient but not immoderate nucleophilicity to react with palladium(II) complexes. This character leads to chemoselective cross-coupling reactions. Organosilicon compounds have a weakly polarized C— Si bond and thus often need activation by a Lewis base to couple with electrophiles. Organolead compounds having electron-withdrawing ligands sometimes act as an electrophile to react with nucleophilic organometallic compounds, giving crosscoupled products.

B. ORGANOSILICON COMPOUNDS[1]–[4]

B.i. Alkenylsilane

Neutral organosilanes (R — SiMe3) are weak nucleophiles among the organometallics described in this section and generally do not undergo a desilylative coupling reaction with aryl halides in the presence of a palladium catalyst except for the following examples. Hallberg and Westerlund[5] reported that although trimethyl(vinyl)silane could transmetalate with an arylpalladium(II) complex to afford coupled products, aryl-substituted alkenylsilanes formed through the Heck type reaction also accompanied (Scheme 1). On the other hand, Kikukawa and co-workers[6] – [8] found that the reaction of trimethyl( - or-styryl)silanes with arenediazonium tetrafluoroborates gave a regioisomeric mixture of coupling products. The catalytic cycle of the reaction is considered to involve carbopalladation toward the C—C double bond of an alkenylsilane by an arylpalladium intermediate followed by tetrafluoroborate-assisted elimination of the silyl group and palladium(0) (Scheme 2).

Handbook of Organopalladium Chemistry for Organic Synthesis, Edited by Ei-ichi Negishi ISBN 0-471-31506-0 © 2002 John Wiley & Sons, Inc.

285

286

III

Pd-CATALYZED CROSS-COUPLING

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2% Pd(OAc)2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4% PPh3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R Et3N (1.4 equiv)

 

 

 

 

 

 

R

 

 

 

 

 

R

 

 

 

SiMe3 +

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DMF, 70125

°C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Me3Si

 

 

 

 

 

 

 

 

 

 

I

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R = H, OMe, NO2, Me

 

 

 

 

5160%

 

 

525%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

ArN2+BF4

Ph

 

 

 

Ph

 

 

 

 

Ph

 

 

Ar

 

 

 

 

 

 

 

5% Pd(dba)2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

MeCN, 25 °C

 

 

 

 

Ar

 

Ar

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SiMe3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ar = Ph

 

 

A

 

 

 

 

 

B

 

 

 

 

C

 

 

 

 

 

 

 

 

 

 

4-Me-C6H4

 

from

58

:

42

:

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4-Br-C6H4

 

 

97100% yield

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4-NO2-C6H4

 

to

86 : 14 : 0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ArN2+BF4

 

 

 

 

A +

B +

 

C

 

 

 

 

 

Ph

 

 

 

 

 

 

 

10% Pd(dba)2

 

 

 

 

 

 

 

 

 

 

 

 

 

SiMe3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MeCN, 25 °C

 

from

70

:

30

:

0

68100% yield

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

to

80

:

20

:

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

ArN2+BF4

 

 

 

 

A +

B +

 

C

 

 

 

 

 

 

 

 

 

 

 

 

10% Pd(dba)2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

from

96

:

0

:

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Me3Si

 

 

 

 

 

MeCN, 25 °C

 

 

96100% yield

 

 

 

 

 

 

 

to

>99

:

0

:

<1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 2

In 1982 Yoshida et al.[9] disclosed that an organofluorosilicate underwent desilylative coupling with iodobenzene in the presence of a palladium catalyst under rather drastic reaction conditions (Scheme 3). Although the nucleophilicity at the carbon atom having a silicate group is apparently enhanced, a mixture of regioisomers resulted.

From the standpoint of organic synthesis, the coupling through carbopalladation of a C—C double bond of alkenysilanes is not useful because the reactions afford a mixture of isomers and the substrate is limited to alkenylsilanes. Hatanaka and Hiyama[10] overcame these drawbacks by using fluoride salts to in situ activate organosilicon compounds. Thus, an alkenyl(trimethyl)silane coupled with an aryl or alkenyl halide in the presence of a palladium catalyst and (Et2N)3S (Me3SiF2) , abbreviated as TASF, with retention of the double bond geometry of both substrates (Scheme 4).[10] Upon activation by a fluoride ion, the nucleophilicity of alkenylsilanes becomes adequate to complete transmetallation. This cross-coupling reaction is tolerant of a wide variety of functional groups such as ester, ketone, aldehyde, and alcohol. Furthermore, mild reaction conditions

III.2.4 OVERVIEW OF OTHER Pd-CATALYZED CROSS-COUPLING PROTOCOLS

287

 

 

 

 

 

 

 

5% Pd(OAc)2

 

 

 

 

 

 

 

 

 

Ph

 

 

10% PPh3

Ph

 

Ph

 

 

 

+ IPh

Et3N

 

K2

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

135 °C, 20 h

 

 

 

 

 

 

 

 

 

SiF5

 

 

 

 

Ph

 

Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

51%

8%

 

 

 

 

 

 

 

 

Scheme 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.5% [PdCl(η3-C3H5)]2

 

 

 

 

 

 

 

 

 

 

IAr

TASF (1.3 equiv)

 

 

 

 

+

 

 

 

 

 

 

 

 

Ar

 

HMPA, 50

°C

 

 

 

SiMe3

 

 

 

 

 

 

Ar = 1-Np

4-Me-C6H4 83–98% 4-NO2-C6H4

4-NH2-C6H4

4-MeCO-C6H4

4-I-C6H4

 

+

I

 

R

 

SiMe3

 

R = n-Hex

 

 

(CH2)8COOMe

 

 

(CH2)9OCOMe

 

 

(CH2)8CHO

 

 

C(=CH2)CH2CH2Ph

 

 

Ph

 

 

I

 

+

 

 

 

 

 

 

+

n-Hex

 

I

 

 

 

SiMe3 +

I

 

 

n-Hex

 

OEt

 

 

 

+

I

 

 

Ph

 

SiMe3

 

Ph

+

I

 

 

Ph

 

SiMe3

 

2.5% [PdCl(η3-C3H5)]2 5% P(OPh)3

TASF (1.3 equiv)

THF, 50 °C

R

52–100%

100%

n-Hex

76%

n-Hex

78%

OEt

Ph 45%

Ph

Ph 32%

Scheme 4

288

III Pd-CATALYZED CROSS-COUPLING

prevent degeneration and/or isomerization of products: thermally labile trienes do not isomerize before the completion of the reaction. n-Bu4N F (TBAF) is equally effective but in some cases inferior to TASF; CsF and KF are futile for diene synthesis.[11] Under similar conditions, alkynyland allyl(trimethyl)silane also reacted with alkenyl or allyl bromides (vide infra).

The following mechanism is suggested for the cross-coupling of alkenylsilanes. Nucleophilic attack of a fluoride ion to the silicon atom of alkenylsilanes should afford a pentacoordinated silicate, whose nucleophilicity of the silicon-substituted carbon and Lewis acidity of silicon are both enhanced to undergo transmetallation effectively through a four-centered transition state (Scheme 5). The importance of Lewis acidity on the silicon is evidenced by the fact that the pentafluorosilicates, which should have sufficient nucleophilicity but lack a coordination site on silicon, were not effective substrates for the cross-coupling reaction (Scheme 3, vide supra).

 

 

 

F

 

 

 

 

 

ArPdX

 

X

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ArPd

 

 

 

 

 

 

ArPdR

R

 

SiMe3

 

 

R

 

 

SiMe3

 

 

 

 

 

SiFMe3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Me3SiF

 

 

 

 

 

 

 

F

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 5

Trimethyl(vinyl)silanes having an aliphatic substituent on vinyl, however, failed to couple with an aryl iodide under similar conditions, probably because they could not afford pentacoordinated silicates efficiently owing to the electron-donating nature of the substituent. To assist the formation of the pentacoordinated intermediates, the methyl group on the silicon atom was replaced by fluorine.[12] The coupling reaction of (E)-1-fluoro(methyl)silyl-1-octene with 1-iodonaphthalene clearly suggested that introduction of one or two fluorine atom(s) on silicon was effective (Scheme 6). Inertness of (E)-1-trifluorosilyl-1-octene is attributed to the formation of an unreactive hexacoordinated silicate. These findings led to the successful coupling reaction of various alkenylsilanes with aryl and alkenyl iodides with complete retention of configuration of both the coupling partners (Scheme 7).

 

I

 

 

 

 

 

n-Hex

 

 

 

 

2.5% [PdCl(η3-C3H5)]2

n-Hex

 

 

 

TASF (1.0 equiv)

 

 

 

+

 

 

 

 

 

 

 

SiMe3-nFn

 

 

 

THF, 50 °C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n

Time (h) Yield (%)

 

 

 

 

 

 

 

 

 

 

 

0

24

0

 

 

 

 

1

10

81

 

 

 

 

2

48

74

 

 

 

 

3

24

0

 

Scheme 6

III.2.4

OVERVIEW OF OTHER Pd-CATALYZED CROSS-COUPLING PROTOCOLS

289

 

 

 

 

I

 

n-Hex

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

or

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

 

n-Hex

 

 

 

 

 

 

 

 

 

 

 

or

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

 

 

 

 

 

 

 

 

 

 

n-Hex

 

SiMe2F [A]

n-Bu

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

or

 

 

 

or

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

 

 

 

 

 

 

 

 

 

 

n-Oct

 

 

SiMe2F [B] +

 

 

 

 

 

 

 

 

 

 

coupling

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

product

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1224 h

 

 

 

 

 

 

 

 

O

 

 

 

 

7489%

 

or

 

 

 

or

 

 

 

 

 

 

 

 

 

 

 

 

 

SiMe2F [C]

 

 

 

 

 

 

O

 

n-Bu

 

I

 

 

 

O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

or

I

[A]2.5% [PdCl(η3-C3H5)]2, TASF (1.5 equiv), THF, 60 °C

[B]5% Pd(PPh3)4, TASF (1.5 equiv), THF, 60 °C

[C]2.5% [PdCl(η3-C3H5)]2, TBAF (1.5 equiv), THF, 60 °C

Scheme 7

The cross-coupling reaction of alkenyl(fluoro)silanes with aryl halides sometimes produces small amounts of cine-coupled products in addition to the desired ipso-coupled products.[13] The cine-coupling is often striking in the reaction with organotin compounds. The isomer ratio of products produced by the reaction of 1-fluoro(dimethyl)silyl-1- phenylethene with aryl iodides is found to depend on the electronic nature of the substituent on aryl iodides (Scheme 8). An electron-withdrawing group like trifluoromethyl and acetyl favors the formation of the ipso-coupled product. To explain the substituent effect, a mechanism is proposed for the transmetallation of alkenylsilanes with palladium(II) complexes and is depicted in Scheme 9. It is considered that an electron-donating substituent on Ar enhances the nucleophilicity of the aryl group to promote an intramolecular nucleophilic attack of Ar to the cationic -carbon (path b), leading to the cine-coupled product.

290

III Pd-CATALYZED CROSS-COUPLING

 

 

 

 

 

 

 

 

 

Ph

 

2.5% [PdCl(η3-C3H5)]2

Ph

 

Ph

 

IAr

TBAF (1.1 equiv)

 

 

 

 

 

 

+

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

THF, 60

°C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FMe2Si

 

 

 

Ar

 

 

 

Ar

 

 

 

 

 

 

 

 

 

 

 

Ar = 4-CF3-C6H4

24 h

72%

93

:

7

 

 

 

 

 

 

4-MeCO-C6H4

20 h

73%

88

:

12

 

 

 

 

 

 

4-F-C6H4

4 h

80%

79

:

21

 

 

 

 

 

 

Ph

4 h

69%

75

:

25

 

 

 

 

 

 

4-Me-C6H4

14 h

84%

59

:

41

 

 

 

 

 

 

4-EtO-C6H4

20 h

63%

60

:

40

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 8

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

FMe2Sia

 

 

 

Ph

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

 

 

Ph

+

 

 

a

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FMe2Si

 

 

 

 

 

 

F

 

 

 

 

 

 

Pd

 

 

 

 

 

 

 

Ar

Pd

Ar

 

 

 

Pd

 

 

b

 

 

 

 

 

 

 

 

 

 

F

 

 

 

 

 

 

 

 

 

Ar

 

 

 

 

Ar

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Si]

 

 

 

 

 

 

 

[Si]

 

 

 

Ar

 

 

 

[Si]

 

Ar

H

 

 

Ph

Ph

 

 

Ar

 

 

 

 

Ph

 

 

 

 

 

 

H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ar

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pd

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

Pd

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pd

 

X

X

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 9

B.ii. Arylsilane

The coupling reaction of arylsilanes with aryl iodides is also mediated by a palladium catalyst and a fluoride ion.[14],[15] Optimized reaction conditions are as follows: (i) two fluorine atoms on silicon are required; (ii) an ethyl or propyl group as a dummy alkyl ligand is preferred, because a methyl group competitively participates in the crosscoupling reaction; and (iii) TBAF, a highly effective fluoride ion source, can be replaced by inexpensive KF. Various unsymmetrical biaryls are synthesized under the conditions (Scheme 10).

Aryl(chloro)silanes, upon pretreatment with KF, smoothly undergo the Pd-catalyzed coupling with aryl bromides and iodides to give various biaryls. For this procedure, Pd(OAc)2 (0.5 mol %)/P(o-tol)3 (0.5 mol %) is convenient (Scheme 11).

Under an atomospheric pressure of carbon monoxide, aryland alkenylsilanes undergo a carbonylative coupling reaction with aryl and alkenyl halides.[16],[17] The optimized conditions for arylsilanes were use of N,N-dimethyl-2-imidazolidinone (DMI) as a solvent and KF as a fluoride ion source (Scheme 12), whereas alkenylsilanes preferred THF and TBAF (Scheme 13).

Recently, Shibata and co-workers[18] found that aryl(trimethoxy)silanes were also applicable to the Pd-catalyzed cross-coupling reaction with aryl bromides (Scheme 14). A similar procedure using phenyl-, vinyland allyl(trialkoxy)silanes was also reported by Mowery and DeShong.[19]

III.2.4 OVERVIEW OF OTHER Pd-CATALYZED CROSS-COUPLING PROTOCOLS

291

5% [PdCl(η3-C3H5)]2

KF (3 equiv)

Ar1SiRF2 + IAr2 Ar1 Ar2 DMF, 70100 °C, 649 h

4594%

Ar1 = Ph

4-Me-C6H4

4-CF3-C6H4

3-MeO-C6H4

R = Et, Pr

Ar2 = 4-EtO-C6H4 2-MeO-C6H4 3-MeO-C6H4 3-HOCH2-C6H4 3-MeCOOCH2-C6H4 4-NC-C6H4 4-MeCOO-C6H4 4-MeCO-C6H4 4-MeOCO-C6H4

3-HCO-C6H4

1-Np

Scheme 10

 

 

KF (5 equiv)

 

0.5% Pd(OAc)2

 

 

 

0.5% P(o-tol)3

Ar1SiEtCl2

+ BrAr2

 

 

 

 

Ar1Ar2

DMF, 60 °C, 3 h

 

 

 

 

120 °C, 18 h

 

 

 

 

 

 

4199%

Ar1 = Ph

Ar2 = 4-NC-C6H4

 

 

 

4-CH3-C6H4

4-CF3-C6H4

 

 

 

4-n-Pent-C6H4

4-F-C6H4

 

 

 

4-CH3O-C6H4

4-MeOCO-C6H4

 

 

 

3-MeO-C6H4

4-MeCO-C6H4

 

 

 

2-Me-C6H4

3-HCO-C6H4

 

 

 

2-NO2-C6H4

2-NC-C6H4 etc...

Scheme 11

2.5% [PdCl(η3-C3H5)]2 CO (1 atm)

KF (1.5 equiv)

Ar1SiR1F2 + IR2

DMI, 100 °C, 525 h

Ar1 = Ph

3-MeO-C6H4

4-CF3-C6H4

4-Me-C6H4

2-thienyl

R1 = Et, n-Pr

R2 = 3-HCO-C6H4 1-Np

4-MeCO-C6H4

4-NC-C6H4

4-MeOCO-C6H4

3-quinolinyl (E)-1-octen-1-yl

Scheme 12

Ar1 R2

O

3880%

THF, 50 °C, 1720 h
+ IR
2.5% [PdCl(η3-C3H5)]2 CO (1 atm)
TBAF (2.0 equiv)

292

III Pd-CATALYZED CROSS-COUPLING

n-Hex

SiF3

R = 3-HCO-C6H4 3-MeO-C6H4 3-HOCH2-C6H4 (E)-2-phenylethen-1-yl

Scheme 13

n-Hex R

O

4371%

Ar1Si(OMe)3

TBAF (1.05 equiv)

THF, r.t., 30 min

 

Ar1 = 4-(4-n-Pr-cyclohexyl)-C6H4 4-(4-n-Pent-cyclohexyl)-C6H4 4-(4-Et-cyclohexyl)-C6H4 4-(4-MeOCH2-cyclohexyl)-C6H4

4-n-Pent-C6H4 4-MeO-C6H4 3,4-F2C6H3

Ar2Br (1.2 equiv) 5% Pd(OAc)2

15% PPh3

Ar1 Ar2

toluene, 120 °C, 3–30 h

6192%

Ar2 = 3,4-F2C6H3 4-MeO-C6H4 4-NO2-C6H4 4-NC-C6H4 4-EtOCO-C6H4 3-pyridyl

4-MeCO-C6H4

Scheme 14

Aryl chlorides that are usually unreactive in Pd-catalyzed cross-coupling reactions are applicable to the reaction with aryland alkenylchlorosilanes using a fluoride ion reagent and a catalytic amount of (i-Pr3P)2PdCl2, (Cy2PCH2CH2PCy2)PdCl2, or [PdCl( 3-C3H5)]2

(Scheme 15).[20]

MeO

 

SiEtCl2

[A] or [B]

Cl

 

COMe

 

 

 

 

Cl

 

 

 

 

 

 

 

 

 

 

 

 

Me

 

SiEtCl2

[A]

 

 

 

COMe

 

 

 

 

 

 

 

 

 

 

+

Cl

 

F

 

 

 

 

 

 

2048 h

 

 

 

 

 

 

 

 

n-Bu

 

SiMeCl2

[C]

 

 

 

F

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cl

 

CF3

n-Hex

 

SiMeCl2

[C]

 

 

 

 

 

 

 

 

 

 

Cl

 

CN

 

 

 

 

 

[A]0.5% PdCl2(i-Pr3P)2, KF (6 equiv), DMF, 120 °C

[B]2.0% PdCl2(Cy2PCH2CH2PCy2), KF (10 equiv), DMF, 120 °C

[C]0.5% [PdCl(η3-C3H5)]2, TBAF (3.6 equiv), THF, 90 °C in a sealed tube

coupling product

5897%

Scheme 15

III.2.4 OVERVIEW OF OTHER Pd-CATALYZED CROSS-COUPLING PROTOCOLS

293

The role of a fluoride ion as an activator and as a ligand on silicon can be played by a hydroxide ion and a chloride ligand, respectively.[21] Thus, the Pd-catalyzed coupling of aryland alkenylchlorosilanes with aryl and alkenyl halides was accomplished in the presence of NaOH under mild conditions (Scheme 16).

R1

 

 

SiR2Cl2

Br

 

 

 

F

X

 

 

 

 

 

 

 

 

R1 = H, MeO, Me,

 

 

 

 

F

 

 

COMe

trans-4-n-Pr-cyclohexyl

 

 

 

 

 

 

 

 

 

X

 

 

 

COMe

Br

CN

R2 = Et, Me

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N

 

 

 

Cl

 

R3

SiMeCl2

X

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R3 = n-Bu, Me3Si

 

 

 

 

 

 

 

 

Me

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CF3

 

 

 

n-Hex

SiEtCl2

Br

 

 

 

Cl

CF3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I

 

 

 

 

 

 

 

 

 

 

 

 

 

 

n-Hex

 

 

 

 

 

 

 

 

 

 

 

CF3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X = I, Br, Cl

 

 

0.52.5% Pd(OAc)2, Pd(OAc)2/2PPh3 or PdCl2(i-Pr3P)2

coupling

 

 

NaOH (6.0 equiv)

 

 

 

 

 

 

product

 

 

 

 

 

 

 

 

5595%

 

 

THF or benzene, 6080 °C, 562 h

 

 

 

 

 

 

Scheme 16

Allyl carbonates (Schemes 17 and 18) and diene monoxides (Scheme 19) were also employed in the Pd-catalyzed coupling reaction of aryland alkenylsilanes.[22],[23] The reaction does not require activation by a fluoride ion or an additional base like a hydroxide ion.

 

 

 

 

 

 

 

5% Pd(OAc)2

 

R1

+ R2OCOO

Ph

5% PPh3

 

 

 

 

SiMen F3-n

 

 

 

 

 

 

DMF, 60

°C, 128 h

 

R1 = n-Hex, Ph

 

 

2

 

 

 

 

 

R

= Et, i-Pr

 

 

 

 

 

R1

Ph

n = 1, 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

EtOCOO

 

 

 

 

 

 

7294%

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SiMeF2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

+

Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

:

4.4

76%

EtOCOO

 

 

 

 

Ph

 

 

 

 

 

 

 

Ph

+

 

 

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

PhCH2O

 

 

 

 

 

PhCH2O

 

PhCH2O

80%

 

 

 

 

 

 

2.5

:

1

 

Scheme 17

294

III

Pd-CATALYZED CROSS-COUPLING

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.5% Pd2(dba)3 CHCl3

 

 

 

Ar SiEtF2

+ EtOCOO

Ph

 

 

 

5% PPh3

 

 

Ar

Ph

 

 

 

 

benzene, 60 °C

 

 

 

Ar = Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8497%

 

 

2-thienyl

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2,5-(MeO)2C6H3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4-Me-C6H4

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PhSiEtF2

EtOCOO

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

+

Ph

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 :

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

93%

 

 

 

EtOCOO

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

52%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EtOCOO

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

33%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EtOCOO

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

40%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 18

 

 

 

 

 

 

 

 

 

 

O

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

2.5% Pd2(dba)3 CHCl3

 

 

 

 

 

 

SiMeF2

 

10% P(OCH2)3CEt

 

 

 

 

 

 

 

 

 

 

benzene, 40 °C

Ph

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ph

 

 

 

 

 

 

 

OH

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OH

 

 

 

 

 

 

 

5.9

:

1

 

 

 

 

 

 

 

59%

 

 

 

 

 

 

O

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.5% Pd2(dba)3 CHCl3

 

 

 

 

 

 

ArSiEtF2

5% PPh3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

benzene, 4060 °C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ar = Ph

 

 

 

 

 

 

 

 

 

 

 

Ar

 

 

 

 

Ar

 

 

+

 

 

 

 

2-thienyl

 

 

 

 

 

 

 

 

OH

 

 

 

 

 

 

2,5-(MeO)2C6H3

 

 

 

 

 

 

 

17.1

: 1

OH

 

 

 

4-Me-C6H4

 

 

 

 

 

 

 

 

5167%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scheme 19

Соседние файлы в папке Negishi E. 2002 Handbook of organopalladium chemistry for organic synthesis