Functionalization of Hydrocarbons by Homogeneous Catalysis

0.05. 0 cm. 3; solvent, 2.5 cm. 3; RhCl(CO)(PMe. 3)2, 5.0. 4 μηιοί; 10. 0. °C. ; an d irradiatio n b y a high-pressure mercury lam p throug h a...
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Functionalization of Hydrocarbons by Homogeneous Catalysis Masato Tanaka and Toshiyasu Sakakura National Chemical Laboratory for Industry, Tsukuba, Ibaraki 305, Japan

Various catalytic functionalizations of hydrocarbons, including alkanes, have been achieved by using the Vaska-type rhodium complex ligated by trimethylphosphine under irradiation. The functionalizations are divided into two categories: insertion of unsaturated compounds to and dehydrogenation from C-H bonds. A possible common intermediate involved in these reactions is a hydridoalkyl complex formed via alkane oxidative addition to RhCl(PMe ) . The catalytic system exhibits unique regioselectivities: terminal selectivity for n­ -alkanes and meta selectivity for substituted benzenes. The use of inert solvents enables us to achieve more than 90% conversion in dehydrogenation of alkanes. 3

2

X X L K A N E S A R E U N R E A C T I V E E N O U G H to be safely used as "inert" solvents, according to most organic chemistry textbooks. Hence, quite a high temperature (500-1000 °C) is required for today's organic chemical industry to use petroleum products (mainly alkanes) as raw materials. In 1982 and 1983, Bergman, Graham, Jones, and co-workers successively reported (1-3) that some coordinatively unsaturated iridium and rhodium complexes can activate even alkane C - H bonds below room temperature (eqs 1-3; C p * is a pentamethylcyclopentadienyl ligand).

Cp*lrH (PMe ) + RH 2

hv

3

0065-2393/92/0230-0181$06. (K) / 0 © 1992 American Chemical Society

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

(1)

182

H O M O G E N E O U S TRANSITION

Cp*lr(CO) + RH 2

METAL CATALYZED

REACTIONS

(2)

R"| "CO H Cp* r

ι

Cp*RhH (PMe ) + RH

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2

(3)

3

Although the oxidative addition of arene C - H bonds with transition metal complexes was described by Chatt, Green, Tolman, and co-workers (4-6), clear examples of alkane oxidative addition had been lacking. Moreover, Bergman (7) reported a very high regioselectivity for a terminal methyl group in the reaction of n-alkane with C p * R h ( P M e ) . This selectivity cannot be attained by conventional methods for alkane activation with radicals or strong acids (8). Since then, alkane oxidative addition has been intensively and extensively studied. The resulting complexes have a carbon-metal bond and seem to be quite promising intermediates in various catalytic organic syntheses. Influenced by these papers, in 1985 we started to investigate selective functionalizations of alkanes triggered by C - H oxidative addition as an elemental step in homogeneous catalysis. 3

When we started the project, some pioneering groups (9-16) had already studied funetionalization of C - H bonds catalyzed by metal complexes, as depicted in eqs 4-10. However, most of them deal with s p C - H bonds of aromatic rings. 2

turnover 31

(4)

(5)

turnover 4.5 Pd(OAc)

2

+ CO + t-BuOOH

^ , AcOH 75°C, 24-72 h C

(other reagents: C0 , 0 ) 2

l

2

turnover 12 In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

12.

Hydrocarbons and Homogeneous Catalysis

TANAKA & SAKAKURA

RMCO) \

/)

+ CH =CH 2

183

12

CO, 250°C. 7 h

2

(7) (other reagents: W „ CH =CHC0 Me, PhCsCPh, Ph C=C=0, Ph-N=C=0, Ph-N0 ) 8

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2

Q

R

2

.

2

£

R °

R

2

lrCI(CO)(PPh )

3 2

100°C, 49 days

0

Ph

R ? '

S L

W

R O'A R^ O

(8)

turnover 13

hv, irH (CO)(Ph PCH CH PPh ) 3



^

0

+

2

2

2

2

â.

0

CHO „ (9) turnover < 2 o (various other complexes of !r, Rh, or Ru show activity)

Ο

lrH [P(i-Pr) ] 5

+ t-BuCH=CH

2

3 2



150°C, 5 days

j + t-BuCH CH

[I

2

3

(10)

turnover 70 Although transfer hydrogénation of ί-butylethylene with alkanes proceeds effectively (eq 10), the reaction is not attractive from a practical viewpoint because it consumes one molecule of ί-butylethylene to make one molecule of alkenes. Other systems have also been reported since 1985 (17-21), as shown in eqs 11-15. However, "productive" functionalization of alkanes is still very rare and has been a challenging subject for organic chemists.

)=v

C F

H ) ^

i J

Ru(Me PCH CH PMe ) 2

2

2

2

2

ΗΝ

140°C, 94 h

Λ /) turnover 3.5

ο

hv, lrH (OCOCF )(PAr ) 2

3

r.t., 7 days

3 2

•*•

/ ~ \ I

*\ —

j

/

+ H

2

turnover 8

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

(12)

184

£

H O M O G E N E O U S TRANSITION M E T A L C A T A L Y Z E D REACTIONS

+ t-BuCH NC

h

hv, Fe(PMe ) (t-BuCH NC)3 3 2

2

2

r.t.

NCH^'Bu

Ο» < Λ

I3)

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turnover 7 '°*sS^ '

lrH [P(i-Pr) ] ^ s

t-BuCH=CH

+

Q

2

3 2

50°C. 24 h

'°>^o'^^ -Bu ,

(14)

turnover 12

X)

I +

Cp ZrR

^

2

(15)

r.t., 25 h

turnover 23

Recently we developed a catalytic system that can transform hydrocar­ bons, including alkanes, to various useful compounds under mild conditions. The system comprises RhCl(CO)(PMe ) and irradiation of near-UV light (Scheme I). This chapter summarizes the progress of our research. 3

c,

:mr * PM

Me P 3

2

Insertion

Ο

R'N*C

R-C-H N-R'

II

II

^CO



R-C-H

R'C»CH

[M]-CO

[M]-CO

c»0

[Μ]

R ;C=CH

1

Dehydrogenation

-H

2

-H

2

Olefin (R = alkyl) R-R (R » aryl)

R'CHasCH -H

2

2

R' SiH 3

-H

2

R-C=C-R' Η Η R-SiR'a

2

R'CHO

R'CH OH + Olefin 2

Scheme I. In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

12.

TANAKA & SAKAKURA

Hydrocarbons and Homogeneous Catalysis

185

Experimental Details Synthesis of the Catalyst. RhCl(CO)(PMe ) was prepared by the reaction of [RhCl(CO) ] with trimethylphosphine in benzene and recrystallized from M e O H at 0 °C. Most of the other Vaska-type rhodium complexes were synthesized similarly. 3

2

2

2

General Procedure. A solution of RhCl(CO)(PMe ) and a reagent (carbon monoxide, isonitrile, acetylene, olefin, hydrosilane, etc.) in a hydrocarbon was irradiated with a high-pressure mercury lamp. Dehydrogenation of alkanes and dehydrogenative coupling of arenes were conducted without any additional reagents under an inert atmosphere. The reactions were carried out in a Pyrex flask with an immersion-type lamp unless otherwise stated. Wavelength-regulated reactions were conducted with a lamp-housed high-pressure mercury lamp through glass filters. The products were identified by comparison of gas chromatographic (GC) retention times in capillary columns and fragmentation patterns of GC-mass spectroscopy (MS) with authentic samples. When authentic samples were not available, products were isolated and characterized by N M R , IR, and mass spectroscopy and elemental analyses. Yields were generally evaluated by using capillary G C with an internal standard.

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3

2

Results and Discussion Carbonylation. Our group, which has been investigating utilization of carbon monoxide (22), first examined insertion of C O to a C - H bond of hydrocarbons (aldehyde synthesis). Several attempts (23-25) have been made to obtain carbonylated products from hydridoalkyl (or aryl) complexes formed via oxidative addition of hydrocarbons (eqs 16-18).

Cp*lr(R)H(PMe ) + CO



Cp*lr(CO)(PMe ) + RH

(16)

lrCI(Ph)H[P(i-Pr) ] + CO



lrCI(Ph)H(CO)[P(i-Pr) ]

(17)

lr(Ph)H(RC0 )(PAr ) + CO



!r(Ph)H(CO)(RC0 )(PAr )

3

3 2

2

3 2

3

3 2

2

3 2

(18)

Because Cp*IrR(H)(PMe ) is an 18-electron complex, the reaction with carbon monoxide resulted in dissociation of R H . Although IrCl(Ph)(H)(PR ) and Ir(RC02)(Ph)(H)(PAr ) could react with carbon monoxide, the resulting 3

3

3

2

2

carbonyl iridium complexes were rather stable and did not produce aldehyde. We investigated the carbonylation of benzene on the following three working hypotheses.

• As a central metal, rhodium would be promising because rhodium complexes are very active for both carbonylation and C - H activation. In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

186

H O M O G E N E O U S TRANSITION M E T A L C A T A L Y Z E D REACTIONS

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• It is desirable that hydridoalkyl complexes formed through oxidative addition of a C - H bond remain coordinatively unsaturated to react further. Hence, the preferred active species before C - H oxidative addition is a 14-electron complex (Scheme II). The same idea is discussed by Felkin, Crabtree, and co-workers in their studies (25, 26) of dehydrogenation of alkanes. • Promotion of oxidative addition would lead to higher catalytic activity. In other words, ligands should be strong electron donors that are resistant to intramolecular C - H oxidative addition.

^Vacant site) Q Q [ M

RCH CH3 2

]



14 electron

RCH CH CHO + [M] 2

2

.1 . RCH CH -[Mj-H 2

2

16 electron

^ ? ^ > ^ RCH«CH + H{M}H 2

Scheme II. \

P M e s ^ ) Q p M e s ^ ) Q p M e > P ^ ^ M e > PBu s PEfe > P P H 0

3

1.00

1.07

3

-o

0.99

0.26

0.56

P(OMe) s P(i-Pr) > Me PCH PMe (dinuclear) 3

0.022

3

2

2

0.020

2

s

0.20

3

0.027

Ph PCH CH PPh 2

2

0.003

s

2

2

0.001

Chart I. Effect of phosphine ligands on the carbonylation of benzene by RhCl(COXPR3)2; relative catalytic activity (room température, 16.5 h).

After extensive studies (27, 28), we discovered that R h C l ( C O ) ( P M e ) under irradiation is the most effective catalyst (Chart I). The effect of the phosphine ligand is remarkable; RhCl(CO)(PMe ) was 30-40 times more active than RhCl(CO)(PPh ) . Highly electron-donating and sterically small phosphines like 1,3,4-trimethylphospholane and 1,3,4-trimethylphospholene were as effective as trimethylphosphine. The results of our mechanistic investigations indicate that the favorable effect of these phosphines results not from the promotion of C - H oxidative addition but from suppression of reductive elimination of hydrocarbons from a hydridoalkylcarbonyl intermediate (eq 19). 3

3

3

RH • RhCl(CO)(PR )

3 2

2

2

2

B

%

;RhCI(CO)(PR )

3 2

^

RCO ,RhCI(PR ) x

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

3 2

(19)

12.

TANAKA & SAKAKURA

Hydrocarbons and Homogeneous Catalysis

187

In the carbonylation of benzene, benzyl alcohol and benzophenone were formed as secondary products from benzaldehyde (eq 20). To clarify the secondary reactions of aldehydes formed, the carbonylation reactions were carried out in the presence of an additional aldehyde (Table I). The formation of alcohols and ketones was clearly demonstrated. Although there was little decarbonylation of aromatic aldehyde, decarbonylation was the main secondary reaction of cyclohexanecarbaldehyde. hv, RhCi(CO)(PMe ) | Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 4, 2015 | http://pubs.acs.org Publication Date: March 1, 1992 | doi: 10.1021/ba-1992-0230.ch012

3 2

+ CO

O~

CH0 +

room temperature

(20)

0~ *° 0 ~ ° ^ 0 O ~ 0 CH

H+

+

Turnover 3h

13.7

0.08

0.00

0.75

18 h

73.7

10.9

6.50

3.72

The most fascinating feature of carbonylation of the C - H bond lies in its regioselectivity. In the carbonylation of pentane or 2-methylpentane, the methyl group was distinguished from the methylenes in nearly 100% selectivity (29, 30). O n the other hand, substituted benzenes like toluene or anisole were carbonylated mainly at the meta position (31). These selectivities, which are entirely different from the selectivity observed in radical or electrophilic reactions, must be a characteristic of C - H oxidative addition to low-valent transition metals. The regioselectivity of this carbonylation can be controlled by the wavelength of irradiation (32). When short wavelength (below 325 nm) was cut off, the weakest C - H bonds were carbonylated: methylene in alkane and benzylic methyl in toluene (eqs 21 and 22). Regioselectivity in the carbonylation of alkanes

( > 295 nm)

18 325 nm 8 ÇH

3

295 nm

U

17

16 CH

3

^Λ*.

15

> 325 nm

3

42 q

"U

41

17

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

(22)

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

Case

toluene benzene benzene

2

benzaldehyde p-tolualdehyde cyclohexanecarbaldehyde

2

R CHO

2

2

2

61 5 trace

2

2

2

R CH OH

l

J

1

2

2

2

26 20 32

1

R COR> [orR CH(OH)R ]

2

WH + C O + R C H O -H> R'CHO + R C H O H + R'COR + R C H O H + R COR + R H + R -R* + ···

2 4 43

2

RH

2

0 0 5

R -R'

NOTE: Reaction conditions were as follows: Rh, 0.7 m M ; arene, 3 0 mL; aldehyde, 0.80 mmol; C O , 1 atm; room temperature; and 16.5 h. All yields are based on the amount of R ^ H O used.

1 2 3

3

Table I. Yields of Secondary Reactions of Aldehydes in the Carbonylation Reaction by the RhCl(COXPMe )r-fcv System

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12.

Hydrocarbons and Homogeneous Catalysis

TANAKA & SAKAKURA

189

The following observations may also be concerned with wavelength ef­

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fect. • Cyclohexane was carbonylated efficiently in a mixture with benzene (eq 23), although cyclohexanecarbaldehyde was barely obtained when cyclohexane was used alone. This carbonylation may have occurred because decarbonylation of the cyclohex­ anecarbaldehyde formed was suppressed by the presence of benzene that absorbs short-wavelength light. • Methyl selectivity for alkanes was lost when they were car­ bonylated as a mixture with benzene (eq 24).

0 / 0

hv, RhCI(CO)(PMe )

3 2

+ c o

1:1 «,rno.)

0" Turnover

CHO +

10.7

^

(

0~ ° OCH2

5.6

+ CO

H+

2

3

)

0~ ~0

CH0 +

Έ

14.2

4.3

hv, RhCI(CO)(PMe )

3 2

r.t., 2 h

1 :1 (moi / mol)

(24)

CHO + PhCHO + PhCH OH 2

Turnover

2.6

0.94

12.3

3.0

In addition to carbon monoxide, other unsaturated compounds like isonitriles and acetylenes can also insert into C - H bonds to give aldimines (eq 25) and substituted alkenes (eq 26), respectively (33, 34).

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

190

H O M O G E N E O U S TRANSITION M E T A L C A T A L Y Z E D REACTIONS

Dehydrogenation of Alkanes. Hydridoalkyl complexes formed through oxidative addition of the C - H bond are expected to be a good intermediate for alkene synthesis as well as aldehyde formation, because alkyl complexes of transition metals readily produce alkenes via β-hydride elimination (Scheme II). As a matter of fact, when alkanes were irradiated in the presence of R h C l ( C O ) ( P M e ) under an inert atmosphere, alkenes and hydrogen were produced quite efficiently (eq 27, Chart II) (35, 36).

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3

hv, RhCI(CO)(PMe ) 3

2

(Q

2

96°C, 6 h

+

H

(27)

2

Turnover 667 (Conversion 6.7%)

PMe 1.00

3

> P/^QyCMe 0.71

> PPh > P h P C H P P h 3

2

0.19

2

0.17

> PBu > M e P C H P M e 3

0.049

2

2

2

#

> P(OMe)

3

0.085

2

e

0.016

> P(i-Pr)

3

0.009

> Ph PCH CH PPh 2

2

2

2

=0

Chart II. Effect of phosphine ligands on the dehydrogenation of cyclooctane by RhClfCOXPRah; relative activity (96 ° C , 6 h, * indicates dinuclear complex). The reaction proceeds well even under H atmosphere. Irradiation must be a driving force to promote the thermodynamically unfavorable reaction. Turnover rate of the dehydrogenation of cyclooctane at room temperature is about 10 times faster than that of the carbonylation of benzene. T h e dehydrogenation can be further accelerated by heating. 2

Catalytic activity significantly depends on the nature of the phosphine ligands of the catalyst; trimethylphosphine is the best ligand, as in the case of carbonylation. The complexes of triphenylphosphine and trimethylphosphite exhibited much higher catalytic activity than expected from the result of the carbonylation. However, because the deactivation of these complexes occurred rather fast, total turnovers achieved in the use of these ligands, especially P(OMe) , were much lower than in the case of P M e . 3

3

When acyclic alkanes were dehydrogenated, internal alkenes were ob­ tained as major isomers. This product resulted partly from the isomerization of a terminal alkene to thermodynamically more stable internal alkenes. Terminal alkenes could be obtained in the presence of additional phosphine ligand at the expense of the reaction rate (eq 28) (37).

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

12.

Hydrocarbons and Homogeneous Catalysis

TANAKA & SAKAKURA

191

hv, RhC!(CO)(PMe ) + PMe 3 2

3

room temp.

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P/Rh Time(h) S^s^S 2

1

7

5

3

70

+

/ v ^ S ^

:

77

(

+

24

g

)

Total turnover

/^S^s

:

2

15

5.4

6

4.0

A principal problem in the hydrocarbon transformation catalyzed by the RhCl(CO)(PMe ) -/iv system is the lack of solvents that are stable in these reactions. Hence, we must use a substrate itself as a solvent. This require­ ment has strongly restricted the achievement of high conversions and ap­ plication of the reactions to expensive or high-melting substrates. We re­ cently developed inert solvents for the dehydrogenation of alkanes (38). In 2,2,5,5-tetramethylhexane, more than 90% conversion was achieved in 3 h for the dehydrogenation of cyclooctane (eq 29). 3

O (2vol.%)

2

hv, RhCI(CO)(PMe )

3 2

100°C, 3h

1

Ο 0

/ — \

+

Yield 59%

/ = \

27%

Conv. 92%

OO 0.65%

+ dimers 5.5% 0.18%

(29)

As the conversion increased, the initially formed cyclooctene further reacted to give 1,3-cyclooctadiene. Regioselective formation of the 1,3-diene is prob­ ably a result of the high reactivity of the allylic C - H bond, although very rapid isomerization of primarily formed unconjugated dienes to the 1,3-diene cannot be excluded. The dehydrogenated product of the solvent, 2,2,5,5tetramethyl-3-hexene, was not detected at all. A quite bulky aromatic hy­ drocarbon like 1,3,5-tri-i-butylbenzene also works as an inert solvent in the dehydrogenation (Table II). Dilution of cyclooctane with 2,2,5,5-tetra­ methylhexane did not significantly reduce the initial turnover rate as com­ pared with the reaction of neat cyclooctane. This comparison strongly sug­ gests that oxidative addition of a C - H bond to the rhodium complex is not the rate-determining step in this dehydrogenation. Because hydridorhodium species are suspected as intermediates in the dehydrogenation of alkanes, hydrogénation of unsaturated compounds using alkanes as hydrogen donors is expected to occur. As a matter of fact, addition

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

b

b

2

(f-BuCH )

2

1,3,5-tri-i-buty lbenzene

2

3

1 3

48

1 3 1 3 7

Time (h)

34 53

42

3

60 92 1.9 90 92

Conversion (%) COE

t-2r 16

3

2

52 (38) 59 1.9 (72) 60 (156) 62

c

7 27 0 21 25 Decenes

1,3-COD

32 (54) 50(84)

c-25 Pentadecenolides

0

c

others 19

1 6 0 9 4

Dimers

Yield (%) (Turnover)

r

b

NOTE: Reaction conditions were as follows: substrate, 0.050 cm ; solvent, 2.5 cm ; RhCl(CO)(PMe ) , 5.04 μηιοί; 100 ° C ; and irradiation by a high-pressure mercury lamp through a Pyrex filter. "Based on the charged amount of the substrate. C O E and C O D are cyclooctene and cyclooctadiene, respectively. ln these cases, 1.26 μπιοί of Rh was used. Regioisomeric mixtures; f-2- and c-2- are trans-2- and cw-2-decene, respectively.

Pentadecanolide

Decane

2

cyelooctane (f-BuCH ) 1,3,5-tri-i-butylbenzene

6

2

Cyelooctane Cyclooctane Cyelooctane

2

(f-BuCH )

Solvent

Cyelooctane

Substrate

Table II. Dehydrogenation of Alkanes in Solvents

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12.

TANAKA & SAKAKURA

of cyclohexene

Hydrocarbons and Homogeneous Catalysis

193

to the dehydrogenation reaction of cyelooctane by the

RhCl(CO)(PMe ) -&v system resulted in the formation of cyclohexane. A l 3

2

dehydes were also reduced to the corresponding alcohols under similar conditions (eq 30, Table III) (39).

j?

3

hv, [Rh] 3

R ^CH OH

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1

+

2

2^VR

R

(30)

Table III. Reduction of Carbonyl Compounds Using Cyelooctane as a Hydrogen Donor Yield (%) Efficiency of Time Conversion Decarbonyfoted ll Transfer' Akohol (h) (%) a

Substrate

b

Cyciohexanecarbaldehyde Pheiiylpropanal Octanal 2-Octanone

24 48 24 48 24 48 24

2

46 36 59 50 47 31 1

1 1 2 3 1 1 0

69 87 45 67 70 89 1

73 94 56 78 72 93 1

NOTE: Reaction conditions were as follows: substrate, 0.1 cm ; cyelooctane, 2.0 cm*; RhCl(CO)(PMe )2, 0.0020 mmol; and irradiation by a high-pressure mercury lamp through UV35 filter at room temperature. "Yields are evaluated by G C analysis and based on the charged amount of substrates. ''Deearbonylated products (mainly alkane). 100 x alcohol/cyclooctene. 1

:i

Although the photoreduction of aldehydes has been extensively studied, simple reduction to the corresponding alcohols is still rare. Ketones were barely reduced under the same conditions. Thus, the chemoselective reduction of aldehyde in the presence of ketone is possible. Furthermore, Wilkinson-type rhodium complexes, R h C l ( P R ) , are known to be inactive 3

3

for the hydrogénation of aldehydes because they are easily deactivated through the formation of Vaska-type complexes, RhCl(CO)(PR ) . Actually, 3

2

R h C l ( C O ) ( P M e ) was inactive even under irradiation for the hydrogénation 3

2

of aldehydes with dihydrogen in benzene. Besides alkene formation from alkane, the RhCl(CO)(PMe ) -/iv system 3

2

can catalyze various dehydrogenative reactions of hydrocarbons (eqs 31-35) (40-44).

Q

+ R SiH 3

hv, [Rh]

/=\ ^y-SiR

3

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

(32)

194

H O M O G E N E O U S TRANSITION

Ο * n-C H 8

1 7

n-CeH^-^*

hv, [Rh] -H

5

CT^CIO Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 4, 2015 | http://pubs.acs.org Publication Date: March 1, 1992 | doi: 10.1021/ba-1992-0230.ch012

(33)

2

2

+

REACTIONS

Q^C0 Me

^C0 Me

^

METAL CATALYZED

(diene)

+

Η

' °

(34) 2

0

(diene)

hv, [Rh]

C0 Me +

^C0 Me

2

»

2

*C0 '

"C0 Me

2

(35)

2

In the dehydrogenative silylation and vinylation of toluene, almost the same regioselectivity was observed as in the carbonylation (o:m:p

=

0:2:1). The formation of an ethyl-branched diene in the dehydrogenative dimerization of 1-decene (eq 34) is associated with the activation of the allylic C - H bond, which was also pointed out for the formation of 1,3-cyclooctadiene (eq 29). The head-to-tail dimerization of methyl propionate possibly proceeds via methyl acrylate generated as an intermediate.

Conclusions We have shown that it is possible to functionalize hydrocarbons under mild conditions by homogeneous catalysis. Further application of C - H oxidative addition to catalysis will probably lead to development of versatile organic synthetic reactions with alkanes. We hope that our research has provided a clue to creation of an entirely new high-efficiency chemical industry. We have

found

that

the

use

of

R h C l ( C H = C H ) ( P M e 3 ) 2 in 2

2

place

of

R h C l ( C O ) ( P M e ) allows dehydrogenation either by visible light irradiation 3

2

or thermally (45).

Acknowledgments The authors heartily thank T. Sodeyama, Y. Tokunaga, F. Abe, K. Sasaki, K. Wada, and K. Ishida for their contribution to the present work.

References 1. Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1982, 104, 352-354. 2. Hoyano, J. K.; Graham, W. A. G. J. Am. Chem. Soc. 1982, 104, 3723-3725.

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 4, 2015 | http://pubs.acs.org Publication Date: March 1, 1992 | doi: 10.1021/ba-1992-0230.ch012

12.

Hydrocarbons and Homogeneous Catalysis

TANAKA & SAKAKURA

195

3. Jones, W. D.; Feher, F. J. Organometallics 1983, 2, 562-563. 4. Chatt, J.; Davidson, J. M. J. Chem. Soc. 1965, 843-855. 5. Berry, M.; Elmitt, K.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1979, 1950-1958. 6. Tolman, C. Α.; Ittel, S. D.; English, A. D.; Jesson, J. P. J. Am. Chem. Soc. 1979, 101, 1742-1751. 7. Periana, P. Α.; Bergman, R. G. J. Am. Chem. Soc. 1986, 108, 7332-7346. 8a. Pines, H . The Chemistry of Catalytic Hydrocarbon Conversions; Academic Press: New York, 1981. 8b. Pryor, W. A. Free Radicals; McGraw-Hill: New York, 1966. 9. Itatani, H.; Yoshimoto, H . J. Org. Chem. 1973, 38, 76-79. 10. Fujiwara, Y.; Moritani, I.; Danno, S.; Asano, S.; Teranishi, S. J. Am. Chem. Soc. 1969, 91, 7166-7169. 11. Fujiwara, Y.; Kawata, I.; Sugimoto, H . ; Taniguchi, H . J. Organomet. Chem. 1983, 256, C35-C36. 12. Hong, P.; Yamazaki, H . J. Mol. Catal. 1984, 26, 297-311. 13. Gustavson, W. Α.; Epstein, P. S.; Curtis, M . D. Organometallics 1982, 2, 884-885. 14. Fisher, B. J.; Eisenberg, R. Organometallics 1983, 2, 764-767. 15. Kunin, A. J . Eisenberg, R. Organometallics 1988, 7, 2124-2129. 16. Crabtree, R. H . Chem. Rev. 1985, 85, 245-269. 17. Jones, W. D.; Kosar, W. P. J. Am. Chem. Soc. 1986, 108, 5640-5641. 18. Burk, M . J.; Crabtree, R. H.; McGrath, D. V. J. Chem. Soc., Chem. Commun. 1985, 1829-1830. 19. Jones, W. D . ; Foster, G . P.; Putinas, J. M . J. Am. Chem. Soc. 1987, 109, 5047-5048. 20. Lin,Y.;Ma, D . ; Lu, X. Tetrahedron Lett. 1987, 28, 3249-3252. 21. Jordan, R. F.; Taylor, D. F. J. Am. Chem. Soc. 1989, 111, 778-779. 22. Tanaka, M . Yuiti Gosei Kagaku Kyokaishi 1987, 45, 716-728. 23. Janowicz, A. H.; Bergman, R. G . J. Am. Chem. Soc. 1983, 105, 3929-3939. 24. Werner, H . ; Hohn, Α.; Dizallas, M . Angew. Chem., Int. Ed. Engl. 1986, 25, 1090-1092. 25. Burk, M . J.; Crabtree, R. H . J. Am. Chem. Soc. 1987, 109, 8025-8032. 26. Felkin, H . ; Fillebeen-Khan, T.; Gault, Y.; Holmes-Smith, R.; Zakrzewski, J. Tetrahedron Lett. 1984, 25, 1279-1282. 27. Sakakura, T.; Tanaka, M . Chem. Lett. 1987, 249-252. 28. Sakakura, T.; Sodeyama, T.; Sasaki, K.; Wada, K.; Tanaka, M . J. Am. Chem. Soc. 1990, 112, 7221-7229. 29. Sakakura, T.; Tanaka, M. J. Chem. Soc., Chem. Commun. 1987, 758-759. 30. Sakakura, T.; Hayashi, T.; Tanaka, M . Chem. Lett. 1987, 859-862. 31. Sakakura, T.; Tanaka, M . Chem. Lett. 1987, 1113-1116. 32. Sakakura, T.; Sasaki, K . Tokunaga, Y.; Wada, K.; Tanaka, M . Chem. Lett. 1988, 155-158. 33. Tanaka, M . ; Sakakura, T.; Tokunaga, Y.; Sodeyama, T. Chem. Lett. 1987, 2373-2374. 34. Tokunaga, Y.; Sakakura, T.; Tanaka, M . J. Mol. Catal. 1989, 56, 305-314. 35. Sakakura, T.; Sodeyama, T.; Tanaka, M . New J. Chem. 1989, 13, 737-745. 36. Sakakura, T.; Sodeyama, T.; Tokunaga, Y.; Tanaka, M . Chem. Lett. 1988, 263-264. 37. Sakakura, T.; Sodeyama, T.; Tanaka, M . Chem. Ind. (London) 1988, 530-531. 38. Sakakura, T.; Ishida, K . Tanaka, M . Chem. Lett. 1990, 585-588. 39. Sakakura, T.; Abe, F.; Tanaka, M. Chem. Lett. 1990, 583-584. ;

;

;

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

196

H O M O G E N E O U S TRANSITION

METAL

CATALYZED

REACTIONS

40. Sakakura, T.; Sodeyama, T.; Tokunaga, Y . ; Tanaka, M. Chem. Lett. 1987, 2211-2214.

41. Sakakura, T.; Tokunaga, Y.; Sodeyama, T.; Tanaka, M. Chem. Lett. 1987, 2375-2378.

42. Sakakura, T.; Sasaki, K.; Tokunaga, Y.; Wada, K.; Tanaka, M. Chem. Lett. 1988, 685-688.

43. Sakakura, T.; Tokunaga, Y.; Sodeyama, T.; Tanaka, M. Chem. Lett. 1988, 885-888.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 4, 2015 | http://pubs.acs.org Publication Date: March 1, 1992 | doi: 10.1021/ba-1992-0230.ch012

44. Sakakura, T.; Sodeyama, T.; Tanaka, M. Chem. Lett. 1988, 683-684. 45. Sakakura, T.; Abe,F.;Tanaka, M. Chem. Lett. 1991, 297-298. RECEIVED

for review October

19, 1990.

ACCEPTED

revised manuscript June 4,

In Homogeneous Transition Metal Catalyzed Reactions; Moser, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

1991.