A novel double insertion of the difluoromethylene unit from trifluoromethylcopper into the carbon-copper bond of perfluoroaryl- and perfluorovinylcopper reagents: Preparation, mechanism and applications of new fluorinated copper reagents

Journal of Fluorine Chemistry 102 (2000) 89±103

A novel double insertion of the di¯uoromethylene unit from

tri¯uoromethylcopper into the carbon±copper bond of

per¯uoroaryl- and per¯uorovinylcopper reagents: preparation,

mechanism and applications of new ¯uorinated copper reagents

Zhen-Yu Yang¹, Donald J. Burton^*

Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA

Received 18 June 1999; received in revised form 7 July 1999; accepted 12 August 1999

Dedicated to Professor Paul Tarrant on the occasion of his 85th birthday

Abstract

Reaction of CF₃Cu with penta¯uorophenylcopper, prepared from CuBr and penta¯uorophenylcadmium C₆F₅CdX, gave the double CF₂

unit insertion product, C₆F₅CF₂CF₂Cu, in 70±80% yields. The insertion reaction also worked well with CF₃MX (M Cd, Zn; X Br, CF₃)

and C₆F₅CdX in the presence of CuBr at room temperature to afford C₆F₅CF₂CF₂Cu. With a vinylcopper analog, (Z)-CF₃CF=CFCu, double

CF₂insertion also occurred resulting in the formation of (E)-CF₃CF=CFCF₂CF₂Cu, which could be trapped with allyl bromide to give (E)-

CF₃CF=CFCF₂CF₂CH₂CH=CH₂. When CF₂=CFCu was used as a substrate, (E)-CF₃CF=CFCF₂CF₂Cu was observed, but in low yield. A

mechanism for this novel double CF₂insertion is proposed to involve a copper di¯uorocarbenoid complex intermediate, which inserted into

the carbon±copper bond of the ¯uorinated phenyl and vinyl coppers to form ¯uorinated benzyl or allyl copper reagents. The intermediate

benzyl or allyl coppers are more reactive than the penta¯uorophenyl or vinylcoppers and rapidly undergo insertion of another CF₂unit.

Per¯uorobenzylcopper was prepared independently and gave C₆F₅CF₂CF₂Cu on reaction with CF₃Cu. The resultant new copper reagent,

such as C₆F₅CF₂CF₂Cu, showed good thermal stability and reactivity. Halogenation of the copper reagent gave the corresponding halides

C₆F₅CF₂CF₂X, and insertion of sulfur dioxide into the carbon±copper bond followed by trapping with allyl halide gave the corresponding

allylic sulfones. C₆F₅CF₂CF₂Cu also participated in coupling reactions with allyl halides, vinyl halides and aryl halides to give the coupled

products in good yields. Selective functionalization of both aryl rings of the ¯uorinated diarylethanes with a variety of reagents has also

Keywords: Fluorinated copper reagents; Penta¯uorophenylcopper; Tri¯uoromethylcopper; Insertion reactions; Coupling reactions

1. Introduction

such as zinc, cadmium and copper reagents have been

developed [1±3]. Among these reagents, per¯uoroalkylcop-

per reagents have received the most attention, since they

exhibit high stability and reactivity and have been the most

versatile for the introduction of the per¯uoroalkyl group into

organic compounds. Preparations of F-alkylcopper com-

pounds have been most generally achieved from per¯uor-

oalkyl iodides as starting materials, although

per¯uorocarboxylate and per¯uoroalkylelemental com-

pounds have been utilized in the preparation of per¯uor-

oalkylcopper reagents [4,5]. Among per¯uoroalkylcoppers,

tri¯uoromethylcopper is the most important and interesting

since it exhibits excellent versatile utility and remarkable

reactivity [6]. Tri¯uoromethylcopper has been widely used

to prepare various tri¯uoromethylated compounds which

The use of organometallic reagents in organic synthesis

has been a dynamic and growing area in organic chemistry.

However, the development of ¯uorinated organometallics

has proceeded at a slower pace and has not reached the

degree of complexity of its hydrocarbon counterparts due to

the lack of suitable precursors and in part to the low thermal

stability of the lithium and magnesium analogs. In the last

decade, thermally stable ¯uorinated organometallic reagents

^*Corresponding author. Tel.: 1-319-335-1363; fax: 1-319-335-1270.

E-mail address: donald-burton@uiowa.edu (D.J. Burton).

¹E.I. Dupont de Nemours, Central Research & Development Depart-

ment, Experimental Station, Wilmington, DE 19880-0328, USA.

PII: S 0 0 2 2 - 1 1 3 9 ( 9 9 ) 0 0 2 4 7 - X

90

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

often exhibit enhanced biological activity [7]. However,

tri¯uoromethylcopper is much less thermally stable than

its higher homologs. Early preparations of this copper

reagent have been achieved from the reaction of tri¯uor-

omethyl iodide, tri¯uoromethylmercury or iododi¯uoro-

methylsulfonyl ¯uoride with copper, but these methods

have either employed expensive reagents or required high

temperatures [8±24]. Recently, Burton and Wiemers

reported a low temperature pre-generative route to tri¯uor-

omethylcopper by in situ metathesis of tri¯uoromethylcad-

mium or zinc reagents, prepared from the reaction of a

di¯uorodihalomethane with cadmium or zinc in DMF with

cuprous halides [25,26]. Although, three different copper

species in DMF solution can be formed, two of them slowly

decomposed at room temperature to afford penta¯uor-

oethylcopper in quantitative yield. The mechanism of the

decomposition reaction has not been investigated in detail,

but it is obvious that a CF₂unit inserts into the carbon±

copper bond. Since tri¯uoromethylcopper reagent acted as a

CF₂unit transfer reagent, it was of interest to determine

whether CF₂could insert into other organometallic reagents

[27]. Herein, we report a novel and ef®cient double insertion

reaction of CF₂into the sp²-carbon±copper bonds to make

new ¯uorinated copper reagents and describe the applica-

tion of these reagents in organic synthesis.

308C in DMF, and the resulting reaction mixture was

slowly warmed to room temperature (1 h). ¹⁹F NMR ana-

lysis of the reaction mixture indicated that the CF₃Cu signal

had disappeared and new signals at 39.9 (t, 29.3 Hz) and

44.6 (s) ppm were observed, indicating the formation of

C₆F₅CF₂CF₂Cu. The insertion reaction was quite clean and

70±80% yields of product (based on C₆F₅Cu) were formed

by ¹⁹F NMR analysis. However, when CF₃Cu was reacted

with C₆F₅Cu at room temperature, an exothermic reaction

occurred, which resulted in the desired product

C₆F₅CF₂CF₂Cu along with signi®cant amounts of

CF₃CF₂Cu. The latter was formed by insertion of the

CF₂unit into CF₃Cu. Since the F-alkyl- or aryl cadmium

reagents and CuBr exchange was rapid, even at low tem-

perature, this insertion reaction could be simpli®ed by in situ

generation of the copper reagents. Thus, upon treatment of

the tri¯uoromethylcadmium or zinc reagent (2 equiv.) with

C₆F₅CdX in the presence of CuBr (3 equiv.) in DMF at room

temperature for 40 min, C₆F₅CF₂CF₂Cu was formed in 70±

80% yields.

CF₃Cu C₆F₅Cu

!

C₆F₅CF₂CF₂Cu ꢁ70 80%

40^ꢀC to RT

CuBr

C₆F₅CdX 2CF₃MX ! C₆F₅CF₂CF₂Cu ꢁ70 80%

RT

where M Cd, Zn and X Br, CF₃.

2. Results and discussions

In the presence of catalytic amounts of CuBr, the reaction

was extremely slow and only trace amounts of the desired

copper reagent were formed. In the absence of CuBr, no

double insertion product was detected under similar condi-

tions. These results indicated that the cadmium or zinc

reagents did not undergo the insertion reaction.

2.1. Insertion of CF₂into the carbon±copper bond of

pentafluorophenylcopper

C₆F₅Cu is completely soluble in a number of organic

solvents and exhibits remarkable thermal stability. The ®rst

synthesis of this reagent was achieved by metathesis reac-

tion of penta¯uorophenyl lithium or magnesium halide with

cuprous halides [28±30]. However, this method requires

pre-generation of the thermally unstable penta¯uorophenyl

lithium or Grignard reagents. Although Rieke prepared the

penta¯uorophenylcopper directly from F-phenyl iodide, a

highly active copper powder and an ethereal solvent were

required [31,32].

We have prepared C₆F₅Cu in DMF without the need for

solvent exchange. The copper reagent is synthesized from

C₆F₅CdX, which is readily prepared from bromopenta¯uor-

obenzene and cadmium powder in DMF at room tempera-

ture [33]. The metathesis reaction of the C₆F₅CdX with

CuBr proceeds smoothly at room temperature to give

C₆F₅Cu in almost quantitative yield [27,34]. C₆F₅Cu pre-

pared from C₆F₅CdX exhibits different reactivity from that

prepared from the corresponding lithium or Grignard

reagents [34]. In this paper C₆F₅Cu is prepared from

C₆F₅CdX in DMF.

The C₆F₅CF₂CF₂Cu reagent was characterized by ¹⁹F

NMR analysis. Although, many per¯uoroalkyl copper

reagents exhibit several ¹⁹F NMR signals in solution,

C₆F₅CF₂CF₂Cu was observed as a single species and the

CF₂Cu group exhibited a singlet at 44.7 ppm (vs. PhCF₃).

Further con®rmation of the structure of C₆F₅CF₂CF₂Cu

was afforded by halogenation. When a solution of

C₆F₅CF₂CF₂Cu was treated with bromine or iodine, the

corresponding bromide, C₆F₅CF₂CF₂Br, and iodide,

C₆F₅CF₂CF₂I, were isolated in 55% and 48% yield, respec-

tively, based on C₆F₅CdX, while with chlorine, a mixture of

C₆F₅CF₂CF₂Cl and C₆F₅CF₂CF₂Br was formed. The for-

mation of C₆F₅CF₂CF₂Br in the latter case is due to oxida-

tion of bromide anion with chlorine in the solution to afford

bromine, followed by reaction with C₆F₅CF₂CF₂Cu.

C₆F₅CF₂CF₂Cu !^Br²C₆F₅CF₂CF₂Br ꢁ55%

I₂

C₆F₅CF₂CF₂Cu ! C₆F₅CF₂CF₂I ꢁ48%

Cl₂

Penta¯uorophenylcopper reagent in DMF solution was

slowly added to two equivalents of CF₃Cu reagent, prepared

by the exchange reaction of CF₃CdX and CuBr at 408C to

C₆F₅CF₂CF₂Cu ! C₆F₅CF₂CF₂Br ꢁ28%

C₆F₅CF₂CF₂Cl ꢁ22%

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

91

2.2. Insertion of CF₂into carbon±copper bond of

fluorovinylcoppers

2.3. Mechanism of the double CF₂insertion reaction

Fluorinated transition metal complexes exhibit dramati-

cally different structural and bonding characteristics in

comparison with their hydrocarbon counterparts [37±41].

Metal±carbon bond distances in ¯uorinated organometallic

reagents are signi®cantly shorter than those of hydrocarbon

analogs, resulting in stronger metal±carbon bonds in the

former case [42]. On the other hand, the acceptor capacity of

the per¯uoroalkyl group causes a drift of dp electrons from

the metal into the C±F antibonding orbitals, weakening the

C±F bonds [43,44]. Clark and Tsai proposed a ``no-bond''

resonance structure (CF₂=MF) based on IR analysis [45]. In

fact, CF₃MX, such as (CF₃)₂Cd, has been used as a di¯uor-

ocarbene source with ole®ns to give di¯uorocyclopropanes

[46].

Successful insertion of CF₂into the carbon±copper bond

of penta¯uorophenylcopper prompted us to study other F-

sp²carbon±copper bonds. We utilized (Z)-penta¯uoropro-

penylcopper as a model. The vinyl copper is easily prepared

by metathesis with copper(I) halide of the analogous vinyl-

cadmium reagent, which is readily obtained by reaction of

the ¯uorinated vinyl iodide and cadmium powder in DMF at

room temperature [35,36]. The tri¯uoromethylcadmium

reagent was slowly added to a solution of the vinyl copper

reagent and CuBr in DMF at 308C and the mixture

warmed to room temperature over several hours. ¹⁹F

NMR analysis of the reaction mixture indicated the pre-

sence of CF₃Cu; the vinylcopper signals had disappeared

and double insertion had occurred to give a new homoallylic

copper reagent with retention of stereochemistry. The two

new CF₂signals were observed at 114 (brs) ppm (vs.

CFCl₃) and 109 (m) ppm, respectively.

Structures of tri¯uoromethylcopper in DMF solution are

more complex than was initially thought [25]. Previous

CF₃Cu formalism for tri¯uoromethylcopper is over-

simpli®ed, i.e., because copper has multiple oxidative

states. Burton and Wiemer previously reported that there

are three copper species in solution after warming the

initially formed tri¯uoromethylcopper [25]. Two of them

were determined to be Cu(I) complexes, which could be

oxidized to form stable multi(tri¯uoromethyl)copper(III)

complexes. The higher oxidative state tri¯uoromethyl-

copper(III) showed different chemical and thermal reactiv-

ity as compared with tri¯uoromethylcopper(I) [47,48].

Tri¯uoromethylcopper(III) failed to decompose to give

CF₃CF₂Cu, although they all coupled with aryl iodides.

The insertion was conducted at low temperature initially

and the active tri¯uoromethylcopper species was freshly

generated CF₃Cu(I). CF₃Cu(I) has lower thermal stability

than tri¯uoromethylcopper(III), since the electron-rich

copper(I) donates more electron density to the C±F

antibonding orbitals, strengthening the C±Cu bond and

weakening the C±F bond. We propose that CF₃Cu(I) is

in equilibrium with a copper di¯uorocarbenoid complex

in solution, although we could not directly observe the

carbenoid species by analysis of the CF₃Cu(I) solution. It

is possible that the carbenoid complex has a short life time

and only transient existence. The copper di¯uorocarbenoid

should have different reactivity than free di¯uorocarbene.

The latter is the most electrophilic dihalocarbene [49,50]

and reacts readily with ole®ns but reacts with electrophiles,

such as halogens, poorly [51]. Copper di¯uorocarbenoid

may alter the reactivity of the carbene±carbon from

electrophilic to nucleophilic [52±54]. In fact, attempts to

trap di¯uorocarbene with tetramethylethylene failed in

the insertion reaction system. In hydrocarbon chemistry,

copper(I) salts have been widely used as catalysts for

cyclopropanations of ole®ns with diazo compounds

[55,56]. A carbenoid with copper(I) was proposed, but never

observed by NMR until Arduengo's recent isolation of

the homoleptic copper±carbene complex [57]. The X-ray

structure of the carbene±copper complex was determined by

In order to con®rm the assigned structure of the homo-

allylic copper reagent, allyl bromide was added to the

reaction mixture, and the partially ¯uorinated diene was

isolated in 48% yield, based on the starting vinylcopper

reagent.

Tri¯uorovinylcopper also reacted with tri¯uoromethyl-

copper in DMF; the only identi®able product was (E)-

CF₃CF=CFCF₂CF₂Cu. Although, the mechanism of forma-

tion of this copper reagent is not entirely clear, we propose

that double CF₂insertion initially forms per¯uorobutenyl-

copper A, which isomerizes by ¯uoride ion catalysis to the

per¯uoroallylcopper B. Another CF₂insertion into B forms

the observed product. Alternatively, single CF₂inserts into

the tri¯uorovinylcopper to form per¯uoroallylcopper, which

isomerized to CF₃CF=CFCu. Then, double insertion of CF₂

affords the ®nal copper reagent. The two reaction pathways

cannot be readily distinguished, but we believe the latter is

less likely since the double insertion is very rapid compared

to isomerization.

92

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

Raubenheimer, and the carbon±copper bond is shorter than

the carbon±copper single bond [58].

Attempts to prepare a stable F-benzylcopper failed at

room temperature. However, upon addition of the solution

of cadmium reagent to CuBr in DMF at 358C to 408C,

the metathesis reaction was rapid and the corresponding

copper reagent was formed in almost quantitative yield as

detected by low temperature ¹⁹F NMR analysis. The reso-

nance for the copper reagent in the ¹⁹F NMR spectrum

exhibited typical aromatic ¯uorines. The CF₂Cu signals

appeared at 24.1 and 28.0 ppm (t, J 22.0 Hz) vs.

C₆H₅CF₃in a 7:1 ratio, indicating two different copper

species, which have been previously observed in many F-

alkyl and allylcopper species in our laboratory. In addition,

the ¹¹¹Cd=¹¹³Cd satellite couplings had disappeared.

Further evidence for the formation of copper reagent was

chemical transformation. Upon addition of allyl bromide to

the copper reagent solution at low temperature, the CF₂Cu

signals disappeared and the allylated product was observed

within 15 min.

Insertion of carbenoids into the carbon±copper bond has

been previously reported [59±61]. Cairncross and Sheppard

reported that reaction of ethyl diazoacetate with penta¯uor-

ophenylcopper gave ethyl(penta¯uorophenyl)acetate in

43% yield after hydrolysis. They did not observe any double

carbene insertion products [30]. From our observation that

the double insertion product C₆F₅CF₂CF₂Cu is formed from

C₆F₅Cu and CF₃Cu, it is assumed that the initially formed

C₆F₅CF₂Cu is more reactive towards insertion than C₆F₅Cu.

When the stoichiometry of C₆F₅Cu and CF₃Cu was ꢂ1:1,

C₆F₅CF₂CF₂Cu was formed in 55% yield and 45% of

C₆F₅Cu remained; the formation of C₆F₅CF₂Cu was not

observed by ¹⁹F NMR analysis of the reaction mixture. To

test our hypothesis, an independent preparation of

C₆F₅CF₂MX was required, and the insertion reaction of the

per¯uorobenzylcopper reagent carried out with CF₃Cu [62].

When per¯uorobenzyl bromide was added to a suspen-

sion of acid-washed cadmium powder in DMF at room

temperature, an exothermic reaction occurred and resulted

in the formation of the per¯uorobenzylcadmium reagent.

The overall ¹⁹F NMR yield of the cadmium reagents, a

mixture of mono and bis reagents, was 85±90%.

The formation of the F-benzylcadmium reagents was

con®rmed via analysis of the ¹⁹F NMR and ¹¹³Cd spectra

of the reaction mixture. The ¹⁹F NMR spectrum exhibited

distinct resonances for three types of aromatic ¯uorines and

one di¯uoromethylene group. Fluorines alpha to cadmium

showed the expected satellite peaks due to coupling with the

¹¹¹Cd=¹¹³Cd isotopes. Although, it was dif®cult in the ¹⁹F

NMR spectrum to distinguish between the mono and bis

cadmium reagents, the ratio could be readily determined via

¹¹³Cd NMR analysis. In the ¹¹³Cd NMR spectrum, the mono

cadmium reagent exhibited a triplet at 241.2 ppm (t,

J 274.5 Hz, DMF, vs. CdSO₄), while pentets were

observed at 218.3 ppm (pent, J 236.8 Hz, DMF, vs.

CdSO₄) for the bis reagent, due to coupling to the four

¯uorines on the a-carbons. The ratio of mono to bis cad-

mium reagents was 69:31. In the ¹⁹F NMR spectrum a

doublet of triplets was observed for the CF₂of the mono

cadmium reagent at 32.0 (dt, J 274.0 Hz, J 24.0 Hz,

vs. C₆H₅CF₃) ppm and the bis cadmium reagent showed a

doublet of triplets at 31.9 (dt, J 236.7 Hz, J 26.0 Hz,

vs. C₆H₅CF₃) ppm.

Since F-benzylcopper is not stable at room temperature, it

is reasonable to propose that C₆F₅CF₂Cu is an intermediate

in the double CF₂insertion reaction, even though it could

not be detected by ¹⁹F NMR analysis at room temperature.

When C₆F₅Cu, CF₃CdX and CuBr were mixed at 308C,

C₆F₅CF₂Cu was not observed, since no insertion reaction

occurred at such low temperature and only CF₃Cu and

C₆F₅Cu were observed by ¹⁹F NMR. However, when CF₃Cu

was added to a solution of pre-generated C₆F₅CF₂Cu at

308C and the mixture slowly warmed to room tempera-

ture, ¹⁹F NMR analysis of the reaction mixture indicated the

formation of C₆F₅CF₂CF₂Cu along with CF₃Cu, C₂F₅Cu

and C₆F₅CF₂Cu decomposition products. This result posi-

tively demonstrated that C₆F₅CF₂Cu was involved as an

intermediate in the insertion reaction.

CF₃Cu , CF₂CuF

C₆F₅Cu CF₂CuF ^s!^lowC₆F₅CF₂Cu

C₆F₅CF₂Cu CF₂CuF ^f!^astC₆F₅CF₂CF₂Cu

Consistent with the formation of the F-benzylcadmium

reagents, hydrolysis of the cadmium reagent solution with

dilute HCl gave a-hydroper¯uorotoluene in quantitative

yield. Treatment with iodine gave a 75% isolated yield of

per¯uorobenzyl iodide. The F-benzylcadmium reagent

readily also undergoes allylation at room temperature to give

4,4-di¯uoro-4-penta¯uorophenyl-but-1-ene in 75% yield.

The F-benzylcadmium reagent in DMF was thermally

stable at room temperature for several days. When heated at

508C overnight, only small amounts decomposed, while

decomposition became rapid above 708C.

In conclusion, tri¯uoromethylcopper may be in equili-

brium with a copper di¯uorocarbenoid, which inserts into

the copper±carbon bond of penta¯uorophenylcopper to

form an active per¯uorobenzylcopper. An additional copper

di¯uorocarbenoid rapidly inserts into per¯uorobenzylcop-

per to give the double insertion product, C₆F₅CF₂CF₂Cu.

2.4. Functionalization of C₆F₅CF₂CF₂Cu

The new copper reagent C₆F₅CF₂CF₂Cu exhibits good

thermal stability at room temperature to 558C. At tempera-

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

93

Table 1

tures >858C it undergoes decomposition reactions. Thus,

Reaction of C₆F₅CF₂CF₂Cu with aryl iodides

C₆F₅CF₂CF₂Cu can be generated in large quantities in DMF

and stored in the absence of oxygen and moisture for several

days at room temperature or below without noticeable

decomposition. Although, C₆F₅CF₂CF₂Cu was prepared

from either CF₃CdX or CF₃ZnX, CF₃ZnX was preferably

used to prepare C₆F₅CF₂CF₂Cu on a large scale due to lower

toxicity of zinc powder.

C₆F₅CF₂CF₂Cu also exhibits high reactivity and can be

functionalized with organic electrophiles to give the corre-

sponding coupled products in moderate to good yields based

on C₆F₅CdX. Allylation of C₆F₅CF₂CF₂Cu with allyl

halides readily gave the partially ¯uorinated alkenes in

good yield. Reaction with 3-chloro-but-1-ene or 1-bromo-

but-2-ene gave only C₆F₅CF₂CF₂CH₂CH=CHCH₃, indicat-

ing regiospeci®city of the allylation. Further evidence for

the regiospeci®city observed in the allylation was provided

by reaction with 3-chloro-3-methyl-but-1-ene and 1-chloro-

3-methyl-but-2-ene, both of which afforded the same pro-

duct C₆F₅CF₂CF₂CH₂CH=C(CH₃)₂. The coupled product

from 3-chloro-but-1-ene and 3-chloro-3-methyl-but-1-ene

resulted from an S_N2⁰type pathway, which is presumably

favored due to the steric hinderance at carbon 3. Similar

regiochemistry with other ¯uorinated organocopper

reagents has been observed previously [63,64].

C₆F₅CF₂CF₂Cu YC₆H₄I ! C₆F₅CF₂CF₂C₆H₄Y

Entry

Y

T (8C)

t (h)

Yield (%)

1

2

H

65

60

70

60

65

10

12

4

53

68

66

54

53

72

45

35

45

30

50

2-CH₃

3-CH₃

4-CH₃

2-NO₂

3-NO₂

4-NO₂

2-C₆H₅

4-C₆H₅

4-OCH₃

4-OCOCH₃

3

4

5

6

3.5

2.2

12

5

7

8

9

10

11

12

4

were obtained. The poor coupling between C₆F₅CF₂CF₂Cu

and triphenylbromoethylene presumably is due to the bulki-

ness of the vinyl bromide.

C₆F₅CF₂CF₂Cu C₆H₅CHCHBr

! C₆F₅CF₂CF₂CHCHC₆H₅ꢁ58%

Reaction of C₆F₅CF₂CF₂Cu with aryl iodides usually

worked well. A variety of substituents on the phenyl ring

did not interfere with the coupling reaction as illustrated in

Table 1. Aryl iodides with electron-withdrawing groups,

such as nitro, usually reacted faster. Electron-releasing

groups on the aryl iodide required a longer reaction time

although both groups gave good yields of the coupled

products.

C₆F₅CF₂CF₂Cu CH₂CHCH₂Br

38%

! C₆F₅CF₂CF₂CH₂CHCH₂

C₆F₅CF₂CF₂Cu CH₃CHCHCH₂Br

41%

! C₆F₅CF₂CF₂CH₂CHCHCH₃

C₆F₅CF₂CF₂Cu CH₃CHClCHCH₂

C₆F₅CF₂CF₂Cu YC₆H₅I

44%

! C₆F₅CF₂CF₂C₆H₅Y ꢁ1 ꢁ35 72%

! C₆F₅CF₂CF₂CH₂CHCHCH₃

C₆F₅CF₂CF₂Cu ꢁCH₃₂CCHCH₂Cl

2.5. Reactions of

2-pentafluorophenyl-1-phenyltetrafluoroethanes

26%

! C₆F₅CF₂CF₂CH₂CHCꢁCH₃

2

C₆F₅CF₂CF₂Cu ꢁCH₃₂CClCHCH₂

36%

2-Penta¯uorophenyl-1-phenyltetra¯uoroethanes 1 are an

interesting class of compounds. They contain both an

electrophilic center, the penta¯uorophenyl group, and a

nucleophilic center, the phenyl ring, although the latter is

deactivated by a per¯uoroalkyl group. Both nucleophilic

and electrophilic reagents could react with this class of

compounds. In addition, the ¯uorines on aliphatic carbons

are activated by adjacent aryl rings, which could react with

Lewis acids such as AlCl₃and TiCl₄.

! C₆F₅CF₂CF₂CH₂CHCꢁCH₃

2

Sulfur dioxide readily undergoes insertion into the

carbon±copper bond of C₆F₅CF₂CF₂Cu to form

C₆F₅CF₂CF₂SO₂Cu, detected by ¹⁹F NMR analysis. The

sul®nate reacted with allyl bromide to give the allyl sulfone

initially. However, the allyl sulfone isomerized during

work-up and puri®cation to give a mixture of allyl and

vinylsulfones in a ratio of 1.4:1.

C₆F₅CF₂CF₂Cu SO₂! C₆F₅CF₂CF₂SO₂Cu

56%

C F CF CF SO CH CHCH

CH₂CHCH₂Br

6

5

2

!

87%

C₆F₅CF₂CF₂SO₂CHCHCH₃

The copper reagent also participated in coupling reactions

with vinyl halides. With b-bromostyene, the coupling reac-

tion occurred smoothly at 708C to give the coupled product

in 70% yield. However, with triphenylbromoethylene under

similar conditions only low yields of the coupled product

2.5.1. Reactions with nucleophiles

Carbon nucleophiles, such as alkyl lithiums, reacted

smoothly with 1 to give substitution products. Substitution

94

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

Table 2

Reactions of C₆F₅CF₂CF₂C₆H₄Y with nucleophiles

C₆F₅CF₂CF₂C₆H₄Y NuX ! 4-NuC₆F₄CF₂CF₂C₆H₄Y

Entry

NuX

Y

Yield (%)

Attempt to acetylate 1 (Y 4-Me) with acetyl chloride in

the presence of TiCl₄in CH₂Cl₂failed. Instead, the ¯uorine±

chlorine exchange product 2 (Y 4-Me) was formed in

high yields. 1-(2-methylphenyl)-2-penta¯uorophenyltetra-

¯uoroethane also underwent chlorine±¯uorine exchange

reaction with TiCl₄in CH₂Cl₂but 1-(3-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane and 1-phenyl-2-penta-

¯uorophenyltetra¯uoroethane remained unchanged with

TiCl₄under similar conditions. However, with a stronger

Lewis acid, such as AlCl₃, the chlorine±¯uorine exchange

proceeded smoothly with 1-(3-methylphenyl)-2-penta¯uor-

ophenyltetra¯uoroethane at room temperature. The halogen

exchange occurred exclusively at the carbon adjacent to the

phenyl ring, suggesting that the exchange reaction involved

a cation intermediate. Since a phenyl ring stabilizes a

benzylic cation better than the penta¯uorophenyl ring,

exchange occurred only at this position.

1

2

PhLi

H

73

80

59

47

42

81

64

72

66

60

MeLi

H

3

3-Me

H

4

MeONa

EtONa

5

6

KOH/EtOH

KOH/t-BuOH

i-PrONa

PhONa

7

H

8

4-Me

H

9

10

11

n-C₆H₁₃NH₂

Et₂NH

2-NO₂

H

occurred exclusively at the para position of the penta¯uor-

ophenyl ring. For example, slow addition of methyl lithium

in ether to a solution of 1 in ether caused the immediate

precipitation of lithium ¯uoride and the formation (in good

yield) of the substitution product. Other lithium reagents

such as phenyl lithium and butyl lithium also readily reacted

with 1 and the results of these substitution reactions are

tabulated in Table 2.

Compound 1 reacted with alkoxide in alcohol at room

temperature to give the substitution product in high yields.

For example, the methoxy product was obtained upon

reaction of 1 with sodium methoxide in methanol and ether

at room temperature for 1 h. With sodium ethoxides or

isopropoxide, 1 gave the corresponding ethoxy- and iso-

propoxy-substituted products, respectively. When reacted

with KOH in ethanol at room temperature, 1 gave the ethoxy

product in 81% yield; no hydroxyl product was detected.

However, when reaction with KOH was carried out in a

mixture of t-butanol and water, the hydroxyl-substituted

product was obtained exclusively. Phenoxide also worked

well to give the phenyl ether in 72% yield.

3. Conclusions

We have discovered a novel double CF₂insertion reaction

of CF₃Cu with the carbon±copper bonds of ¯uorinated

phenyl and vinyl copper reagents. The insertion reaction

has been proposed to involve a di¯uorocarbenoid copper

complex intermediate, which transferred a CF₂into a car-

bon±copper bond to form ¯uorinated benzyl or allyl copper

reagents. The selectivity of CF₂insertion into C₆F₅CF₂Cu

and CF₂=CFCF₂Cu is remarkable. The benzylic and allylic

copper reagents are more reactive than C₆F₅Cu and

CF₂=CFCu and readily undergo the second insertion of

CF₂. The insertion process stops cleanly once a primary

alkylcopper reagent is formed. From our experience with

CF₂insertion into R_FCF₂Cu higher temperatures facilitate

insertion into R_FCF₂Cu. Since the insertion reactions

described herein were conducted at 08C to RT, competitive

insertions into C₆F₅CF₂CF₂Cu and CF₃CF=CF₂CF₂CF₂Cu

were not observed. These resultant new copper reagents

have shown good thermal stability and reactivity. Halogena-

tions of the copper reagent gave the corresponding halides

C₆F₅CF₂CF₂X, and insertion of sulfur dioxide into carbon±

copper bond followed by trapping by allyl halide gave allyl

sulfones. C₆F₅CF₂CF₂Cu also participated in coupling reac-

tions with allyl halides, vinyl halides and aryl halides to give

the coupled products in good yields. Selective functionali-

Amines also displaced ¯uorine in the para-position of the

penta¯uorophenyl ring. When 1 was reacted with excess

hexylamine at 608C for 4 h, the corresponding amine was

formed in 66% yield. Diethyl amine gave the substitution

product in 60% yield under similar conditions.

2.5.2. Reactions with electrophiles or MClx (M Al or Ti,

x 3,4)

Electrophilic reactions of 1 is relatively dif®cult due to

deactivation of the phenyl ring by the per¯uoroalkyl group.

With bromine, 1 (Y H) gave no brominated product. With

the slightly activated 4-methyl phenyl ring 1 (Y 4-Me),

bromination occurred in CCl₄in the presence of iron, giving

the corresponding brominated product in 71% yield.

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

95

zation of both aryl rings of the ¯uorinated diarylethanes

with a variety of reagents has been also demonstrated.

(75 mmol) of CuBr. Then, 25 mmol of a penta¯uorophe-

nylcadmium reagent in 25 ml of DMF and 50 mmol of a

tri¯uoromethylzinc reagent in 42 ml of DMF were added

and the resultant reaction mixture was stirred at 08C to room

temperature for 30 min. ¹⁹F NMR analysis of the reaction

mixture indicated that C₆F₅CF₂CF₂Cu reagent was formed

in 73% yield. Then, 4.0 g (25 mmol) of bromine in 10 ml of

DMF were added slowly with stirring at 08C over 15 min,

the reaction mixture stirred at room temperature for an

additional 10 min, and then ¯ash distilled at reduced pres-

sure (1 mm Hg) to give a light yellow distillate, which was

poured into a 200 ml of water. The organic layer was

separated and washed twice with water to give 5.2 g

(80%) of C₆F₅CF₂CF₂Br, b.p.: 76±788C/40 mm Hg. ¹⁹F

NMR (CDCl₃): 67.2 (t, J 4.9 Hz, 2F), 107.8 (t,

J 3.17 Hz, 2F), 137.1 (m, 2F), 146.2 (m, 1F),

159.7 (m, 2F) ppm; ¹³C NMR (CDCl₃): 177.51 (tt,

J 311.4 Hz, J 41.4 Hz, CF₂), 114.32 (tt, J 261.3 Hz,

J 34.7 Hz, CF₂) ppm; FT±IR (CCl₄): 1528 (m), 1508

4. Experimental

4.1. General

Materials. Aryl iodides, vinyl and allyl halides were

purchased from Aldrich and used directly. All reactions

were monitored by ¹⁹F NMR analysis of the reaction

mixtures on a 90 MHz spectrometer. The ¹H, ¹⁹F, and

¹³C NMR spectra of ®nal products were obtained on a

90 MHz spectrometer (CFCl₃, or TMS internal references).

FT±IR were recorded as CCl₄solutions in a 0.1 cm path

length cell. ¹¹³Cd NMR spectra were recorded at 19.84 MHz

(CdSO₄external reference). Low resolution mass spectra

analyses were performed at 70 eV in the electron-impact

mode on a single quadrapole instrument interfaced to a gas

chromatograph ®tted with an OV-101 column. High resolu-

tion mass spectra analyses were performed by the Univer-

sity of Iowa High Resolution Mass Spectroscopy Facility at

70 eV in the electron impact mode. GLPC analysis were

performed on a 5% OV-101 column and thermal conduc-

tivity detector. Melting points were obtained on a capillary

melting point apparatus in open-ended capillaries and are

uncorrected.

(s), 1334 (m), 1175 (m), 1000 (s); GC±MS: 348 (M ,

1.6), 346 (M , 1.7), 217 (100), 179 (12.1), 167 (12.7),

117 (30.0).

4.1.3. Reaction of C₆F₅CF₂CF₂Cu with chlorine

A two-necked ¯ask ®tted with a stir bar and a N₂inlet was

charged with 4.5 g (45 mmol) of CuCl and 15 mmol of

penta¯uorophenylcadmium reagent in 15 ml of DMF.

30 mmol of tri¯uoromethylzinc reagent in 30 ml of DMF

were added and the resultant reaction mixture was stirred at

08C to room temperature for 30 min. Chlorine gas was

condensed into the reaction mixture at 08C using a dry-

ice/IPA (IPA isopropyl alcohol) condenser. The resultant

reaction mixture was allowed to stir for 20 min and then

¯ash distilled at reduced pressure (1 mm Hg) to give a light

yellow distillate, which was poured into water. The organic

layer was separated and washed with water to give, after

drying, 2.5 g of products. ¹⁹F NMR analysis indicated a

mixture of C₆F₅CF₂CF₂Br (28% yield) and C₆F₅CF₂CF₂Cl

(22% yield). ¹⁹F NMR (CDCl₃) for C₆F₅CF₂CF₂Cl: 72.1

(t, J 5.1 Hz, 2F), 105.1 (t, J 31.7 Hz, 2F) ppm: GC±

4.1.1. Reaction of C₆F₅CdX with CF₃CdX and CuBr:

preparation of 1-iodo-2-pentafluorophenyltetrafluoroethane

A three-necked ¯ask, cooled in an ice-water bath, was

®tted with a stir bar and an Ar inlet and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent [33] and 40 mmol of the tri¯uoro-

methylcadmium reagent [25] were added and the

resultant reaction mixture was stirred at room temperature

for 40 min. ¹⁹F NMR analysis of the reaction mixture

indicated the formation of a 78% yield of C₆F₅CF₂CF₂Cu

(DMF, vs. C₆H₅CF₃): 39.0 (t, J 29.3 Hz, 2F), 44.6 (s,

2F), 77.2 (m, 2F), 90.1 (m, 1F), 101.1 (m, 2F). Then,

4.2 g (17 mmol) of iodine were added, the reaction mixture

stirred at room temperature for 2 h, and then ¯ash distilled at

reduced pressure (1 mm Hg) to give a light yellow distillate,

which was poured into a 200 ml of water. The organic layer

was separated and the aqueous layer was extracted with

CH₂Cl₂. The combined organic layers were washed twice

with water and dried over anhydrous MgSO₄. After rotary

evaporation of the CH₂Cl₂, the residue (4.1 g) was distilled

to give 3.4 g (48%) of C₆F₅CF₂CF₂I, b.p.: 78±848C/18 mm

Hg. ¹⁹F NMR (CDCl₃): 61.5 (s, 2F), 99.9 (t, J

31.7 Hz, 2F), 137.2 (m, 2F), 146.5 (m, 1F), 159.9

MS: 304 (M , 1.1), 302 (M , 3.1), 217 (100), 179 (21.9),

167 (17.4), 87 (14.8), 85 (42.8).

4.1.4. Preparation of (E)-4,4,5,5,6,7,8,8,8-nonafluoro-

1,6-octadiene

(Z)-CF₃CF=CFCu prepared from 10 mmol of (E)-

CF₃CF=CFI in 10 ml of DMF was slowly added to 20 mmol

of CF₃Cu in 30 ml of DMF at 308C to 508C. After the

addition was complete, the mixture was slowly warmed to

room temperature. ¹⁹F NMR analysis of the reaction mix-

ture indicated the presence of (E)-CF₃CF=CFCF₂CF₂Cu,

which was reacted with 10 mmol of allyl bromide at

room temperature. The reaction mixture was ¯ash

distilled at reduced pressure to give a distillate, which

was poured into water. The organic layer was separated,

washed with water, and dried to give 1.0 g of crude (E)-

(m, 2F) ppm. GC±MS: 394 (M , 12.9), 267 (50.0), 217

(100), 179 (17.7), 167 (17.0), 127 (16.5), 117 (30.5).

4.1.2. 1-Bromo-2-pentafluorophenyltetrafluoroethane

A three-necked ¯ask, cooled in an ice-water bath, was

®tted with a stir bar and an Ar inlet and charged with 10.5 g

96

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

CF₃CF=CFCF₂CF₂CH₂CH=CH₂. ¹⁹F NMR: 68.7 (ddt,

J 21.4 Hz, J 9.2 Hz, J 1.2 Hz, 3F), 114.2 (dt,

J 18.9 Hz, J 6.1 Hz, 2F), 119.4 (dd, J 25.0 Hz,

J 9.8 Hz, 2F), 155.0 (dm, J 139 Hz, 1F), 160.1

(dm, J 139 Hz, 1F) ppm. ¹H NMR: 3.0 (tdm, J 19 Hz,

J 7 Hz, 2H), 5.8 (ddt, J 17 Hz, J 10 Hz, J 7 Hz,

1H), 5.41 (dtd, J 17 Hz, J 3 Hz, J 1 Hz, 1H), 5.35 (d,

J 10 Hz, 1H) ppm. ¹³C NMR: 122.9 (s, CH₂), 126.5 (t,

J 4 Hz, CH), 35.4 (t, J 22 Hz, CH₂) ppm.

4.1.6. 5-(Pentafluorophenyl)-4,4,5,5-tetrafluoro-pent-1-ene

A three-necked ¯ask ®tted with a stir bar and a N₂inlet

was cooled in an ice-water bath and charged with 10.8 g

(75 mmol) of CuBr. Then, 25 mmol of penta¯uorophenyl-

cadmium reagent in 25 ml of DMF and 50 mmol of the

tri¯uoromethylcadmium reagent in 45 ml of DMF were

added and the resultant reaction mixture was stirred at

08C to room temperature for 40 min; then 2.4 g (20 mmol)

of allyl bromide was added and the reaction mixture stirred

at 658C for 4.5 h followed by ¯ash distillation at reduced

pressure to give a distillate, which was poured into water.

The organic layer was separated and washed with water

after drying to give 2.4 g (38%) of product. ¹⁹F NMR

(CDCl₃): 107.6 (t, J 31.7 Hz, 2F), 114.3 (m, 2F),

138.5 (m, 2F), 149.0 (m, 1F), 161.3 (m, 2F) ppm.

¹H NMR (CDCl₃): 5.92±5.78 (m, 1H), 5.36±5.30 (m, 2H),

3.93 (td, J 18.3 Hz, J 7.0 Hz, 2H) ppm. ¹³C NMR

(CDCl₃): 126.62 (t, J 4.4 Hz, CH=), 121.72 (CH=),

118.40 (tt, J 249.9 Hz, J 36.1 Hz, CF₂), 116.04 (tt,

J 257.1 Hz, J 38.9 Hz, CF₂), 25.15 (t, J 23.0 Hz,

CH₂) ppm. FT±IR (CCl₄): 3089 (w), 1655 (s), 1526 (s),

1509 (s), 1333 (s), 1181 (s), 1138 (s), 1093 (s), 1054 (s), 995

4.1.5. Reaction of C₆F₅CF₂CF₂Cu with SO₂and allyl

bromide

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 10.5 g

(75 mmol) of CuBr. Then, 25 mmol of penta¯uorophenyl-

cadmium reagent in 25 ml of DMF and 50 mmol of tri-

¯uoromethylzinc reagent in 42 ml of DMF were added and

the resultant reaction mixture was stirred at 08C to room

temperature for 30 min. Excess SO₂gas was condensed into

the reaction mixture at 08C using a dry-ice/IPA condenser

and the resultant reaction mixture was allowed to stir at

558C for 1.5 h. ¹⁹F NMR (C₆H₅CF₃, internal reference)

analysis indicated that C₆F₅CF₂CF₂SO₂Cu [( 44.1 (t,

J 31.7 Hz, 2F), 67.3 (s, 2F) ppm] was formed in 56%

yield based on the penta¯uorophenylcadmium reagent.

After addition of 2.4 g (20 mmol) of allyl bromide, the

reaction mixture was stirred at room temperature overnight

and C₆F₅CF₂CF₂SO₂CH₂CH=CH₂[( 43.9 (t, J 31.7 Hz,

2F), 52.9 (t, J 9.7 Hz, 2F) ppm] was formed in 87%

yield (based on C₆F₅CF₂CF₂SO₂Cu) by ¹⁹F NMR (vs.

C₆H₅CF₃) analysis of the reaction mixture. The reaction

mixture was evacuated and the residue was diluted with

CH₂Cl₂. Solids were removed by ®ltration and washed

with CH₂Cl₂. The combined organic layers were

washed with water and dried over MgSO₄. After evapora-

tion of the CH₂Cl₂, the residue was puri®ed by silica

gel chromatography (CH₂Cl₂:hexane 1:3) to give 3.2 g

of a mixture of C₆F₅CF₂CF₂SO₂CH₂CH=CH₂[A] and

C₆F₅CF₂CF₂SO₂CH=CHCH₃[B] in a 4.1:1 ratio. ¹⁹F

NMR (CDCl₃): A: 104.8 (t, J 32.0 Hz, 2F), 114.5

(t, J 8.0 Hz, 2F), 137.5 (m, 2F), 146.2 (t, J 20.8 Hz,

1F), 160.0 (t, J 18.2 Hz, 2F); B 104.5 (t, J 31.3 Hz,

(s); GC±MS: 308 (M , 14.7), 217 (78.4), 167 (12.0), 91

(100), 71 (33.0), 41 (6.7).

4.1.7. 5-Pentafluorophenyl-1,2-dibromo-5,5,4,4-

tetrafluoropentane

A mixture of 0.4 g (1.3 mmol) of 5-(penta¯uorophenyl)-

4,4,5,5-tetra¯uoro-1-pentene and 0.4 g (2.5 mmol) of bro-

mine in 2 ml of CHCl₃was stirred at room temperature

overnight. The solvent was evaporated to give 0.6 g (90%)

of product, 100% GLPC purity. ¹⁹F NMR (CDCl₃): 108.1

(t, J 31.7 Hz, 2F), 114.4 (m, 2F), 138.1 (m, 2F),

1

147.5 (m, 1F), 160.3 (m, 2F) ppm. H NMR (CDCl₃);

4.51±3.21 (m) ppm. FT±IR (CCl₄): 1550±1505 (m), 1250

(m), 1185 (s), 1090 (m), 1000 (s); GC±MS: 466 (M , 0.2),

468 (M , 0.3), 470 (M , 0.2), 217 (100), 167 (14.5).

4.1.8. 6-(Pentafluorophenyl)-5,5,6,6-tetrafluoro-hex-2-ene

A three-necked ¯ask ®tted with a stir bar and a N₂inlet

was cooled in an ice-water bath and charged with 4.3 g

(30 mmol) of CuBr. Then, 10 mmol of the penta¯uorophe-

nylcadmium reagent in 10.5 ml of DMF and 20 mmol of the

tri¯uoromethylzinc reagent in 18 ml of DMF were added

and the resultant reaction mixture stirred at 08C to room

temperature for 40 min. Then, 1.3 g (15 mmol) of 3-chloro-

but-1-ene was added to the reaction mixture and mixture

stirred at room temperature overnight. Flash distillation of

the reaction mixture at reduced pressure gave a distillate,

which was poured into water. The organic layer was sepa-

rated, washed with water and dried to give 1.4 g (44%) of

product. ¹⁹F NMR (CDCl₃): 107.8 (t, J 31.4 Hz, 2F),

114.6 (m, 2F), 138.3 (m, 2F), 149.0 (m, 1F), 161.2

(m, 2F) ppm. ¹H NMR (CDCl₃): 5.81±5.70 (m, 1H), 5.50±

5.40 (m, 1H), 2.84 (td, J 18.4 Hz, J 7.0 Hz, 2H), 1.73

(d, J 6.4 Hz, 3H) ppm. ¹³C NMR (CDCl₃): 133.47 (CH=),

2F),

116.0 (m, 2F),

137.5 (m, 2F),

146.6 (t,

J 20.4 Hz, 1F), 160.3 (t, J 18.0 Hz, 2F) ppm. ¹H

NMR (CDCl₃): A: 5.95±5.81 (m, 1H), 5.66±5.57 (m,

2H), 4.06 (d, J 7.2 Hz, 2H) ppm. B: 7.29 (dq,

J 15.1 Hz, J 7.0 Hz, 1H), 6.43 (d, J 15.1 Hz, 1H),

2.15 (dd, J 7.0 Hz, J 1.5 Hz, 3H) ppm. ¹³C NMR

(CDCl₃): A: 127.70 (CH=), 120.85 (CH=), 56.41 (CH₂)

ppm. B: 156.12 (CH=), 124.23 (CH=), 18.47 (CH₃) ppm.

FT±IR (CCl₄): 2943 (w), 1656 (m), 1527 (s), 1510 (s), 1504

(s), 1370 (s), 1334 (s), 1207 (s), 1178 (s), 1111 (s), 1000 (s);

GC±MS: A: 372 (M , 1.4), 248 (4.3), 217 (37.0), 179 (5.3),

117 (5.1), 105 (94.7), 41 (100); B: 372 (M , 2.2), 248 (4.4),

217 (39.2), 179 (7.3), 105 (78.4), 41 (100).

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

97

118.70 (t, J 4.0 Hz, CH=), 118.20 (tt, J 250.7 Hz,

J 35.8 Hz, CF₂), 33.83 (t, J 22.9 Hz, CH₂), 18.17

(CH₃) ppm. FT±IR (CCl₄): 2936 (w), 1656 (s), 1524 (s),

1506 (s), 1427 (s), 1333 (s), 1182 (s), 1158 (s), 1089 (s), 997

(s); GC±MS: 322 (M , 9.4), 217 (92.0), 167 (17.6), 77

(67.9), 69 (12.6), 55 (100).

Similarly, the C₆F₅CF₂CF₂Cu prepared from 20 mmol

of penta¯uorophenylcadmium reagent and 40 mmol of

tri¯uoromethylzinc reagent in the presence of 40 mmol

of CuBr in 47.7 ml of DMF was treated with 20 mmol

of 1-bromo-but-2-ene to give 2.6 g (41%) of the same

product.

washed with water (4 Â 300 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, the black brown solid was

puri®ed by silica gel chromatography (CH₂Cl₂:hexane

1:10) and recrystallized from a mixture of CH₂Cl₂and

hexane to give 2.7 g (53%) of product; m.p. 125±1268C;

¹⁹F NMR (CDCl₃): 107.0 (t, J 31.7 Hz, 2F), 112.4 (t,

J 9.8 Hz, 2F), 138.2 (m, 2F), 148.3 (m, 1F), 160.7

1

(m, 2F) ppm. H NMR (CDCl₃): 7.46 ppm. FT±IR (CCl₄);

1655 (w), 1525 (vs), 1200±1090 (s), 1000(s); GC±MS: 344

(M , 1.5), 217 (5.6), 167 (2.1), 127 (100), 77 (5.5).

4.1.11. 1-(2-Nitrophenyl)-2-pentafluorophenyltetrafluoro-

ethane

4.1.9. 2-Methyl-6-(pentafluorophenyl)-5,5,6,6-

tetrafluoro-hex-2-ene

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

zinc reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.7 g

(15 mmol) of 2-nitroiodobenzene was added and the reac-

tion mixture stirred at 708C for 4 h. The reaction ¯ask was

then equipped with a distillation head and evacuated to

remove DMF. The residue was diluted with 400 ml of

dichloromethane, and solids were removed by suction ®l-

tration and CH₂Cl₂(2 Â 50 ml). The combined organic

layers were washed with water (4 Â 300 ml) and dried over

MgSO₄. After evaporation of the CH₂Cl₂, a black brown

solid was obtained, which were further puri®ed by silica gel

chromatography (CH₂Cl₂:hexane 1:9) and recrystallized

from a mixture of CH₂Cl₂and hexane to give 3.1 g (53%) of

product; m.p. 112±1138C. ¹⁹F NMR (CDCl₃): 106.0 (t,

J 31.8 Hz), 107.7 (s, 2F), 138.3 (m, 2F), 147.4 (m,

1F), 160.4 (m, 2F) ppm. ¹H NMR (CDCl₃) ppm: 7.74; FT±

IR: 1530 (s), 1510 (s), 1200 (m), 1120±1100 (s), 995 (m);

A three-necked ¯ask ®tted with a stir bar and a N₂inlet

was cooled in an ice-water bath and charged with 6.3 g

(45 mmol) of CuBr. Then, 15 mmol of the penta¯uorophe-

nylcadmium reagent in 15 ml of DMF and 20 mmol of the

tri¯uoromethylzinc reagent in 31 ml of DMF were added

and the resultant mixture stirred at 08C to room temperature

for 30 min. Then, 1.6 g (15 mmol) of 1-chloro-3-methyl-

but-2-ene was added, the reaction mixture was stirred at

room temperature overnight. Flash distillation of the reac-

tion mixture at reduced pressure gave a distillate, which was

poured into water. The organic layer was separated, washed

with water, dried, and distilled to give 1.4 g (26%) of the

product. ¹⁹F NMR (CDCl₃): 107.39 (t, J 31.7 Hz, 2F),

114.4 (m, 2F), 138.3 (m, 2F), 148.7 (m, 1F), 161.0

1

(m, 2F) ppm. H NMR (CDCl₃): 5.20 (t, J 7.3 Hz, 1H),

2.87 (td, J 18.6 Hz, J 7.1 Hz, 2H), 1.78 (s, 3H), 1.70 (s,

3H) ppm. ¹³C NMR (CDCl₃): 139.42 (CH=), 118.81 (tt,

J 250.7 Hz, J 34.8 Hz, CF₂), 111.93 (CH=), 29.42 (t,

J 32.9 Hz, CH₂), 25.71 (CH₃), 18.08 (CH₃): FT±IR

(CCl₄); 2936 (m), 1656 (s), 1527 (s), 1506 (s), 1333 (s),

GC±MS: 389 (M , 20.1), 217 (100), 172 (35.8), 153 (16.0),

1182 (s), 1088 (s), 1001 (s); GC±MS: 336 (M , 4.8), 217

(33.8), 167 (6.0), 119 (4.8), 69 (100), 41 (41.1).

142 (8.4), 114 (11.0); Anal: calcd. for C₁₄H₄F₉NO₂: C,

43.20; H, 1.04; F, 43.94; N, 3.60; Found: C, 43.69; H, 1.14;

F, 43.90; N, 3.43.

Similarly, C₆F₅CF₂CF₂Cu prepared from 15 mmol of

penta¯uorophenylcadmium reagent and 30 mmol of tri-

¯uoromethylzinc reagent in the presence of 45 mmol of

CuBr in 46 ml of DMF was treated with 3-chloro-3-methyl-

but-1-ene to give 1.8 g (36%) of product.

4.1.12. 1-(3-Nitrophenyl)-2-pentafluorophenyltetrafluoro-

ethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of penta¯uorophenyl-

cadmium reagent and 40 mmol of the tri¯uoromethylcad-

mium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.7 g

(15 mmol) of 3-nitroiodobenzene was added and the reac-

tion mixture was stirred at 55±608C overnight. The ¯ask was

equipped with a distillation head and evacuated to remove

DMF. The residue was diluted with 400 ml of dichloro-

methane, and the solids were removed by suction ®ltration

and CH₂Cl₂(2 Â 50 ml). The combined organic layers were

washed with water (4 Â 300 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, a black brown solid was

obtained, which were further puri®ed by silica gel chroma-

4.1.10. 1-Phenyl-2-pentafluorophenyltetrafluoroethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

zinc reagent were added, and the resultant reaction mixture

stirred at room temperature for 40 min. Then, 3.1 g

(15 mmol) of iodobenzene was added and the reaction

mixture stirred at 708C for 4 h. The reaction ¯ask was then

equipped with a distillation head and evacuated to remove

DMF. The residue was diluted with 400 ml of dichloro-

methane, and solids were removed by suction ®ltration and

CH₂Cl₂(2 Â 50 ml). The combined organic layers were

98

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

tography (CH₂Cl₂:hexane 1:9) and recrystallized from a

mixture of CH₂Cl₂and hexane to give 4.2 g (72%) of

product; m.p. 1228C, ¹⁹F NMR (CDCl₃): 106.3 (t,

J 31.7 Hz, 2F), 112.0 (t, J 9.7 Hz, 2F), 137.9 (m,

2F), 146.9 (m, 1F), 160.0 (m, 2F) ppm; ¹H NMR: 8.52±

8.14 (m) ppm. FT±IR: 1635 (w), 1530 (s), 1500 (s), 1190

111.7 (t, J 9.8 Hz, 2F); 138.2 (m, 2F), 148.2 (m,

1F), 160.7 (m, 2F) ppm. ¹H NMR (CDCl₃): 7.64 (d,

J 8.5 Hz, 2H); 7.24 (d, J 8.5 Hz, 2H), 2.33 (s, 3H)

ppm. FT±IR: 1765 (m), 1505 (s), 1100 (m), 995 (m); GC±

MS: 402 (M , 2.4), 360 (13.6), 217 (24.7), 167 (2.9), 143

(100), 43 (8.7).

(m), 1100±1090 (m), 985 (m); GC±MS: 389 (M , 11.8), 172

(43.8), 167 (8.0), 114 (15.6).

4.1.15. 1-(2-Methylphenyl)-2-pentafluorophenyl-

tetrafluoroethane

4.1.13. 1-(4-Nitrophenyl)-2-pentafluorophenyltetrafluoro-

ethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then 3.3 g

(15 mmol) of 2-methyliodobenzene was added and the

mixture was stirred at 55±608C overnight. The reaction

¯ask was equipped with a distillation head and evacuated

to remove DMF. The residue was diluted with 400 ml of

dichloromethane, and solids were removed by suction ®l-

tration and CH₂Cl₂(2 Â 50 ml). The combined organic

layers were washed with water (4 Â 300 ml) and dried over

MgSO₄. After evaporation of the CH₂Cl₂, 6.9 g of the black

brown solid was puri®ed by silica gel chromatography

(CH₂Cl₂:hexane 1:2) and recrystallized from a mixture

of CH₂Cl₂and hexane to give 3.7 g (68%) of product, m.p.

1058C. ¹⁹F NMR (CDCl₃): 106.4 (t, J 31.8 Hz, 2F),

107.3 (s, 2F), 138.5 (m, 3F), 148.4 (m, 1F), 160.8

(m, 2F) ppm. ¹H NMR (CDCl₃): 7.29 (m, 4H), 2.49 (s, 3H)

ppm. FT±IR: 1535 (s), 1505 (s), 1200 (m), 1100 (m), 1060

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of penta¯uorophenyl-

cadmium reagent and 40 mmol of the tri¯uoromethylzinc

reagent were added and the resultant mixture stirred at room

temperature for 40 min. Then, 3.7 g (15 mmol) of 4-nitroio-

dobenzene was added and the reaction mixture stirred at

658C for 2.5 h. The reaction ¯ask was then equipped with

distillation head and evacuated to remove DMF. The residue

was diluted with 400 ml of dichloromethane, and solids

were removed by suction ®ltration and CH₂Cl₂(2 Â 50 ml).

The combined organic layers were washed with water

(4 Â 300 ml) and dried over MgSO₄. After evaporation of

the CH₂Cl₂, black brown solids were obtained, which were

further puri®ed by chromatography on silica gel

(CH₂Cl₂:hexane 1:10) and recrystallized from a mixture

of CH₂Cl₂and hexane to give 2.6 g (45%), m.p. 1098C; ¹⁹

F

NMR (CDCl₃): 106.3 (t, J 31.7 Hz, 2F); 112.4 (t,

J 9.7 Hz, 2F), 138.2 (m, 2F), 147.1 (m, 1F), 160.1

1

(m, 2F) ppm. H NMR (CDCl₃): 8.39 (d, J 8.3 Hz, 2H);

(m), 990 (m); GC±MS: 358 (M , 2.1), 217 (6.5), 167 (2.1),

141 (100), 91 (12.3), 77 (1.1).

7.85 (d, J 8.3 Hz, 2H) ppm. FT±IR: 1530 (s), 1510 (s),

1340 (s), 1200 (s); 1100 (s), 1000 (m); GC±MS: 389 (M ,

15.3); 217 (81.6), 172 (100), 167 (6.5), 156 (32.6), 142

(31.6), 114 (37.3).

4.1.16. 1-(3-Methylphenyl)-2-pentafluorophenyl-

tetrafluoroethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.3 g

(15 mmol) of 3-methyliodobenzene was added and the

mixture was stirred at 55±608C overnight. The reaction

¯ask was equipped with a distillation head and evacuated

to remove DMF. The residue was diluted with 400 ml of

dichloromethane, and solids were removed by suction ®l-

tration and CH₂Cl₂. The combined organic layers were

washed with water and dried over MgSO₄. After evapora-

tion of the CH₂Cl₂the black brown solid was puri®ed by

silica gel chromatography (CH₂Cl₂:hexane 1:2) and

recrystallized from a mixture of CH₂Cl₂and hexane to give

3.6 g (66%) of the product, m.p. 126±1278C., ¹⁹F NMR

4.1.14. 1-(4-Acetoxyphenyl)-2-pentafluorophenyl-

tetrafluoroethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

zinc reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.9 g

(15 mmol) of 4-acetoxyphenyl iodide was added and the

reaction mixture was stirred at 658C for 4 h. The reaction

¯ask was then equipped with a distillation head and evac-

uated to remove DMF. The residue was diluted with 400 ml

of dichloromethane, and solids were removed by suction

®ltration and CH₂Cl₂(2 Â 50 ml). The combined organic

layers were washed with water (4 Â 300 ml) and dried over

MgSO₄. After evaporation of the CH₂Cl₂, the black brown

solid was puri®ed by silica gel chromatography

(CH₂Cl₂:hexane 1:9) and recrystallized from a mixture

of CH₂Cl₂and hexane to give 3.0 g (50%) of product; m.p.

1198C. ¹⁹F NMR (CDCl₃): 106.7 (t, J 31.7 Hz, 2F),

(CDCl₃):

J 9.8 Hz, 2F),

106.9 (t, J 31.8 Hz, 2F),

112.1 (t,

148.4 (m, 1F),

138.1 (m, 2F),

1

160.8 (m, 2F) ppm. H NMR (CDCl₃): 1545 (s), 1515

(s), 1230 (s), 1200 (s), 1100 (w), 1010 (s); GC±MS: 358

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

99

(M , 4.1), 167 (2.1), 91 (65); Anal: calcd. for C₁₅H₇F₈:

C, 50.29; H, 1.97; F, 47.74; Found: C, 50.05; H, 1.99; F,

47.26.

(m); GC±MS: 374 (M , 3.6), 217 (1.9), 167 (1.9), 157 (100),

114 (9.2); Anal: calcd. for C₁₅H₇F₉O: C, 48.14; H, 1.88; F,

45.70; Found: C, 48.66; H, 1.86; F, 44.26.

4.1.17. 1-(4-Methylphenyl)-2-pentafluorophenyl-

tetrafluoroethane

4.1.19. 1-(2-Phenylphenyl)-2-pentafluorophenyl-

tetrafluoroethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.3 g

(15 mmol) of 4-methyliodobenzene was added and the

mixture was stirred at 658C overnight. The reaction ¯ask

was equipped with a distillation head and evacuated to

remove DMF. The residue was diluted with 400 ml of

dichloromethane, and solids were removed by suction ®l-

tration and CH₂Cl₂(2 Â 50 ml). The combined organic

layers were washed with water (4 Â 300 ml) and dried over

MgSO₄. After evaporation of the CH₂Cl₂, the black brown

solid was puri®ed by silica gel chromatography

(CH₂Cl₂:hexane 1:8) and recrystallized from a mixture

of CH₂Cl₂and hexane to give 2.9 g (54%) of product; m.p.

135±1368C; ¹⁹F NMR (CDCl₃): 107.0 (t, J 31.7 Hz,

2F); 112.1 (t, J 9.8 Hz, 2F), 138.2 (m, 2F), 148.5

(m, 1F), 160.8 (m, 2F) ppm. ¹H NMR: 7.49 (d, J 8.1 Hz,

2H), 7.28 (d, J 8.1 Hz, 2H), 2.42 (s, 3H) ppm. FT±IR:

1550 (s), 1515 (s), 1265 (m), 1105 (m), 1085 (m), 1015 (s);

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 4.2 g

(15 mmol) of 2-phenyliodobenzene was added and the

mixture was stirred at 658C overnight. The reaction ¯ask

was equipped with a distillation head and evacuated to

remove DMF. The residue was diluted with 400 ml of

dichloromethane, and solids were removed by suction ®l-

tration and CH₂Cl₂. The combined organic layers were

washed with water (4 Â 300 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, the black brown solid was

puri®ed by silica gel chromatography (CH₂Cl₂:hexane

1:5) and recrystallized from a mixture of CH₂Cl₂and

hexane to give 2.2 g (35%) of product; m.p. 97±988C.

¹⁹F NMR: 103.7 (s, 2F), 105.6 (t, J 31.7 Hz, 2F),

138.1 (m, 2F), 148.7 (m, 1F), 160.7 (m, 2F) ppm. ¹H

NMR: 7.63±7.31 ppm. FT±IR: 1540 (s), 1520 (s), 1215 (m),

1015 (m); GC±MS: 420 (11.2), 217 (9.7), 203 (27.1), 183

(100), 167 (2.3), 152 (2.2).

GC±MS: 358 (M , 1.4), 217 (6.2), 167 (2.0), 141 (100), 91

(8.7).

4.1.20. 1-(4-Phenylphenyl)-2-pentafluorophenyl-

tetrafluoroethane

4.1.18. 1-(4-Methoxyphenyl)-2-pentafluorophenyl-

tetrafluoroethane

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 4.2 g

(15 mmol) of 4-phenyliodobenzene was added and the

mixture was stirred at 658C overnight. The ¯ask was

equipped with a distillation head and evacuated to remove

DMF. The residue was diluted with 400 ml of dichloro-

methane, and solids were removed by suction ®ltration and

CH₂Cl₂(2 Â 50 ml). The combined organic layers were

washed with water (4 Â 300 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, the black brown solid was

puri®ed by silica gel chromatography (CH₂Cl₂:hexane

1:5) and recrystallized from a mixture of CH₂Cl₂and

hexane to give 2.8 g (45%), m.p. 172±1748C; ¹⁹F NMR:

106.8 (t, J 31.7 Hz, 2F); 112.2 (t, J 9.8 Hz, 2F),

138.0 (m, 2F), 148.2 (m, 1F), 160.6 (m, 2F) ppm. ¹H

NMR: 7.70±7.41 (m); FT±IR (CCl₄): 1527 (m), 1507 (s),

1425 (s), 1334 (s), 1294 (s), 1193 (s), 1096 (s), 1002 (s);

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 3.7 g

(15 mmol) of 3-nitroiodobenzene was added and the mix-

ture was stirred at 658C overnight. The reaction ¯ask was

equipped with a distillation head and evacuated to remove

DMF. The residue was diluted with 400 ml of dichloro-

methane, and solids were removed by suction ®ltration and

CH₂Cl₂(2 Â 50 ml). The combined organic layers were

washed with water (4 Â 300 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, the black brown solid was

puri®ed by silica gel chromatography (CH₂Cl₂:hexane

1:8) and recrystallized from a mixture of CH₂Cl₂and

hexane to give 1.7 g (30%) of product; m.p. 117±1188C.

¹⁹F NMR (CDCl₃): 107.0 (t, J 31.7 Hz, 2F); 111.4 (t,

J 9.8 Hz, 2F), 138.1 (m, 2F), 148.7 (m, 1F), 160.9

(m, 2F); ¹H NMR: 7.52 (d, J 8.8 Hz, 2H), 6.98 (d,

J 8.8 Hz, 2H), 3.86 (s, 3H) ppm. FT±IR: 1550 (m),

1505 (s), 1295 (m), 1255 (m), 1185 (s), 1100 (m), 1000

GC±MS: 420 (M , 5.9), 217 (4.4), 203 (100), 152 (11.4), 97

(11.6), 81 (28.6), 69 (54.3).

100

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

4.1.21. 1-Phenyl-4-pentafluorophenyl-3,3,4,4-tetrafluoro-

but-1-ene

4.1.24. 3-(Pentafluorophenyl)-3,3-difluoro-but-1-ene

0.6 g (5 mmol) of allyl bromide was added to a solution of

3.3 mmol of C₆F₅CF₂CdX in 6 ml of DMF and the resultant

mixture was stirred at room temperature overnight. The

reaction mixture was ¯ash distilled (2 mm Hg) to give a

distillate, which was poured into 10 ml of water and

extracted with CH₂Cl₂(3 Â 15 ml). The combined organic

layers were washed with water dried over molecular sieves.

After evaporation of the CH₂Cl₂, the residue was distilled to

give 0.62 g (73%) of product, b.p. 89±908C/33 mm Hg,

99.3% GLPC purity. ¹⁹F NMR (CDCl₃): 90.0 (m, 2F),

140.7 (m, 2F), 151.4 (t, J 20.5 Hz, 1F), 161.4 (m,

2F) ppm. ¹H NMR (CDCl₃): 5.85±5.72 (m, 1H), 5.29±5.17

(m, 2H), 3.01 (td, J 15.5 Hz, J 6.7 Hz, 2H) ppm. ¹³C

NMR (CDCl₃): 172.74 (t, J 5.4 Hz, CH=), 122.17 (CH=),

120.25 (t, J 248.0 Hz, CF₂), 43.39 (t, J 36.1 Hz, CH₂)

ppm. FT±IR (CCl₄): 3090 (w), 1655 (s), 1502 (s), 1332 (s),

1269 (s), 1184 (s), 1177 (s), 1138 (s), 1093 (s), 1054 (s), 999

A three-necked ¯ask ®tted with a stir bar and an Ar inlet

was cooled in an ice-water bath and charged with 8.4 g

(60 mmol) of CuBr. Then, 20 mmol of the penta¯uorophe-

nylcadmium reagent and 40 mmol of the tri¯uoromethyl-

cadmium reagent were added and the resultant mixture was

stirred at room temperature for 40 min. Then, 2.7 g

(15 mmol) of b-bromostyrene was added and the mixture

was stirred at 608C overnight. The reaction ¯ask was

equipped with a distillation head and evacuated to remove

DMF. The residue was diluted with 200 ml of dichloro-

methane, and solids were removed by suction ®ltration and

CH₂Cl₂(2 Â 200 ml). The combined organic layers were

washed with water (3 Â 200 ml) and dried over MgSO₄.

After evaporation of the CH₂Cl₂, 7.1 g of the black liquid

was obtained, which was puri®ed by silica gel chromato-

graphy (CH₂Cl₂:hexane 1:2) to give 4.8 g of a yellow

solid. After recrystallization from ethanol, 3.2 g (58%) of

white solid product was obtained, m.p. 92±938C; ¹⁹F NMR

(CDCl₃): 107.2 (t, J 31.7 Hz, 2F); 112.4 (m, 2F),

138.2 (m, 2F), 148.3 (m, 1F), 160.4 (m, 2F) ppm.

¹H NMR: 7.40 (s), 6.6±4.8 (m); FT±IR: 3010 (w), 1645 (w),

1520 (s), 1500 (s), 1180 (s), 1090 (m), 975 (m).

(s); GC±MS: 258 (M , 9.6), 217 (100), 194 (17.0), 167

(7.9), 117 (9.3), 41 (21.6).

4.1.25. Perfluorobenzylcopper reagents

An NMR tube was charged with 42 mg (0.3 mmol) of

CuBr under N₂; then 0.3 mmol of C₆F₅CF₂CdX in 0.5 ml of

DMF solution was added at 508C. After being shaken, the

NMR tube was kept at 358 to 408C for 40 min. ¹⁹F NMR

analysis of the reaction mixture ( 358C) indicated a mix-

ture of C₆F₅CF₂Cu and C₆F₅CF₂CdX. After 1.2 h at 458C,

the ¹⁹F NMR spectrum revealed only the copper reagent,

which contained two different species A and B in a 7:1 ratio.

¹⁹F NMR (DMF, vs. C₆F₅CF₃): 24.1 (t, J 22.0 Hz,

1.75F) ppm. for A; 28.0 (t, J 22.0 Hz, 0.25F) for B,

82.8 (m, 2F), 97.7 (m, 1F), 102.4 (br, 2F).

4.1.22. Preparation of perfluorobenzylcadmium reagents

A ¯ask ®tted with a stir bar and a N₂inlet was charged

with 0.24 g (2 mmol) of cadmium and 2 ml of DMF. Then,

0.3 g (1 mmol) of C₆F₅CF₂Br was added and resultant

mixture was stirred at room temperature (exothermic reac-

tion) for 1.5 h. ¹⁹F NMR analysis (vs. C₆H₅CF₃as internal

reference) of the reaction mixture indicated that 85±90% of

the cadmium reagents were formed. C₆F₅CF₂CdBr: ¹⁹F

NMR (DMF, C₆H₅CF₃):

32.0 (dt, J 274.0 Hz,

J 24.0 Hz, 2F), 82.5 (dt, J 22.6 Hz, J 22.6 Hz,

2F), 97.7 (t, J 22.0 Hz, 1F), 103.1 (m, 2F) ppm.

¹¹³Cd NMR (DMF, CdSO₄): 241.2 ppm (t, J 274.5 Hz).

(C₆F₅CF₂)₂Cd: ¹⁹F NMR (DMF, C₆H₅CF₃): 31.9 (dt,

J 236.7 Hz, J 26.0 Hz, 2F), 82.0 (dt, J 23.1 Hz,

J 26.0 Hz, 2F), 97.6 (t, J 22.3 Hz, 1F), 103.0 (m,

2F) ppm. ¹¹³Cd NMR (DMF, CdSO₄): 218.3 ppm (pent,

J 236.8 Hz).

4.1.26. 1-Phenyl-2-(4-phenyltetrafluorophenyl)-

tetrafluoroethane

A ¯ask ®tted with a stir bar and an Ar inlet was charged

with 0.34 g (1 mmol) of 1-phenyl-2-penta¯uorophenyltetra-

¯uoroethane and 5 ml of ether. Then, 0.5 ml (1 mmol) of

C₆H₅Li in cyclohexane and ether were added at 08C and the

resultant mixture stirred for 30 min. The reaction mixture

was diluted with 25 ml of ether, washed with water and

dried over MgSO₄. After evaporation of the ether, the

residue was recrystallized from CHCl₃to give 0.29 g

4.1.23. Iodoperfluorotoluene

1.27 g (5 mmol) of iodine was added to a solution of

3.3 mmol of C₆F₅CF₂CdX in 6 ml of DMF and the resultant

mixture stirred at room temperature overnight. The reaction

mixture was ¯ash distilled (2 mm Hg) to give a distillate,

(73%) of product. ¹⁹F NMR (CDCl₃):

107.1 (t,

J 31.8 Hz, 2F); 112.2 (t, J 7.3 Hz, 2F), 139.6 (m,

1

2F), 143.1 (m, 2F) ppm. H NMR (CDCl₃): 7.51 ppm.

FT±IR (CCl₄): 1540 (s), 1480(s), 1220 (m), 985 (s) ppm.

Ê

which was washed with water ®ve times and dried over 3 A

GC±MS: 392 (M , 0.3), 217 (23.0), 175 (64.8), 173 (100),

103 (15.3), 77 (8.6), 51 (4.4).

molecular sieves to give 0.85 g (69%) of product. ¹⁹F NMR

(CDCl₃): 37.1 (t, J 31.8 Hz, 2F), 139.7 (m, 2F),

148.8 (t, J 22.0 Hz, 1F), 160.0 (m, 2F) ppm. FT±IR

(CCl₄): 1523 (s), 1504 (s), 1331 (s), 1188 (s), 1127 (s), 1078

4.1.27. 1-Phenyl-2-(4-methyltetrafluorophenyl)-

tetrafluoroethane

(s), 1000 (s); GC±MS: 325 (M F, 2.7), 217 (100), 198

(7.1), 167 (19.5), 148 (10.3), 127 (11.9), 117 (30.3), 69

(10.5).

A ¯ask ®tted with a stir bar and an Ar inlet was charged

with 0.34 g (1 mmol) of 1-phenyl-2-penta¯uorophenyltetra-

¯uoroethane and 10 ml of ether. Then, 0.8 ml (1.2 mmol) of

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

101

CH₃Li was added at 08C and the resultant mixture stirred for

4.1.31. 1-Phenyl-2-(4-ethoxytetrafluorophenyl)-

tetrafluoroethane

1 h. The reaction mixture was poured into 30 ml of ether,

washed with water and dried over MgSO₄. After evapora-

tion of the ether, 0.24 g (80%) of product was obtained: ¹⁹F

NMR (CDCl₃): 107.2 (t, J 31.7 Hz, 2F), 112.5 (t, J

9.8 Hz, 2F), 140.9 (m, 2F), 142.8 (m, 2F) ppm. ¹H NMR

(CCl₄): 7.35 (s, 5H), 2.32 (s, 3H) ppm. FT±IR (CCl₄): 1540

(m), 1485 (s), 1285 (m), 1135 (m), 1070 (m), 1000 (m); GC±

A mixture of 0.28 g (0.8 mmol) of 1-phenyl-2-penta-

¯uoro-phenyltetra¯uoroethane and 0.28 g (5 mmol) of

KOH in 10 ml of ether and 2 ml of ethanol was stirred at

room temperature overnight. The reaction mixture was

diluted with 25 ml of ether, washed with water and dried

over MgSO₄. After evaporation of the ether, the residue was

recrystallized from hexane to give 0.24 g (81%) of product;

¹⁹F NMR: 106.8 (t, J 31.7 Hz, 2F), 112.6 (t, J

9.8 Hz, 2F), 140.9 (m, 2F), 157.0 (m, 2F) ppm. ¹H

NMR (CDCl₃): 7.53 (s, 5H), 4.37 (q, J 6.9 Hz, 2H), 1.45

(t, J 6.9 Hz, 3H) ppm. FT±IR: 2980 (w), 1540 (m), 1490

(s), 1200 (s), 1115 (m), 1090 (m), 1000 (s); GC±MS: 370

MS: 340 (M , 2.6), 213 (6.0), 163 (6.3), 127 (100), 77 (8.8).

4.1.28. 1-(3-Methylphenyl)-2-(4-methyltetrafluorophenyl)-

tetrafluoroethane

A ¯ask ®tted with a stir bar and an Ar inlet was charged

with 0.15 g (0.42 mmol) of 1-(3-methylphenyl)-2-penta-

¯uorophenyltetra¯uoroethane and 10 ml of ether. Then,

0.7 ml (1.0 mmol) of CH₃Li was added at 08C and the

resultant mixture stirred for 1 h. The reaction mixture

was poured into 30 ml of ether, washed with water and

dried over MgSO₄. After evaporation of the ether, 0.09 g

(59%) of product was obtained; ¹⁹F NMR (CDCl₃): 107.1

(t, J 31.7 Hz, 2F), 112.2 (t, J 9.7 Hz, 2F), 141.1 (m,

2F), 142.8 (m, 2F) ppm. ¹H NMR (CDCl₃): 7.37 (s, 4H),

2.42 (s, 3H), 2.33 (s, 3H) ppm. FT±IR: 2940 (w), 1540 (m),

(M , 4.0), 243 (11.9), 215 (33.2), 167 (2.6), 127 (100.0),

117 (3.6), 77 (9.2).

4.1.32. 1-(3-Methylphenyl)-2-(4-ethoxytetrafluorophenyl)-

tetrafluoroethane

A mixture of 0.29 g (0.8 mmol) of 1-(3-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane and 2 mmol of sodium

ethoxide in 7 ml of EtOH and 2 ml of ether was stirred at

room temperature for 40 min. After the solvent was evapo-

rated, the residue was diluted with 30 ml of ether, washed

with water and dried over MgSO₄. After evaporation of the

ether, the residue was recrystallized from ethanol to give

0.13 g (42%) of product; ¹⁹F NMR (CDCl₃): 106.7 (t,

J 31.7 Hz, 2F), 112.2 (s, 2F), 140.6 (m, 2F), 156.7

(d, J 12.2 Hz, 2F) ppm. ¹H NMR: 7.38 (m, 4H), 4.45 (m,

2H), 2.43 (s, 3H), 1.46 (m, 3H) ppm. FT±IR: 2970 (w), 1530

(m), 1485 (s), 1185 (m), 1010 (m), 1090 (m), 995 (m); GC±

1485 (s), 1295 (m), 1080 (m), 1020 (m); GC±MS: 354 (M ,

4.9), 213 (14.3), 163 (18.1), 141 (100), 91 (13.7).

4.1.29. 1-Phenyl-2-(4-hydroxytetrafluorophenyl)-

tetrafluoroethane

A mixture of 0.34 g (1 mmol) of 1-phenyl-2-penta¯uoro-

phenyltetra¯uoroethane 0.33 g (6 mmol) of KOH in 10 ml

of t-BuOH and 1 ml of water was stirred at 608C for 15 h.

After the solvent was evaporated, the residue (0.8 g) was

diluted with 30 ml of ether, washed with a saturated NH₄Cl

solution and dried over MgSO₄. After evaporation of the

ether, 0.44 g of solids were obtained, which was recrystal-

lized from hexane to give 0.27 g (81%) of product; ¹⁹F NMR

MS: 384 (M , 4.5), 215 (17.3), 141 (100), 91 (4.7).

4.1.33. 1-(4-Methylphenyl)-2-(4-isopropoxytetrafluoro-

phenyl)-tetrafluoroethane

A mixture of 0.36 g (1 mmol) of 1-(4-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane and 3 mmol of sodium

isopropoxide in 4 ml of isopropyl alcohol and 4 ml of ether

was stirred at room temperature for 2 h. After the solvent

was evaporated, the residue was diluted with 30 ml of ether,

washed with water and dried over MgSO₄. After evapora-

tion of the ether, the residue (0.37 g) was recrystallized from

ethanol to give 0.27 g of (64%) product; ¹⁹F NMR (CDCl₃):

106.8 (t, J 31.8 Hz, 2F), 112.2 (t, J 8.7 Hz, 2F),

140.7 (m, 2F), 156.0 (d, J 12.2 Hz, 2F) ppm. ¹H NMR

(CDCl₃); 7.40 (d, J 8.1 Hz, 2H), 7.28 (d, J 8.1 Hz, 2H),

4.71 (m, 1H), 2.42 (s, 3H), 1.99 (d, J 5.9 Hz, 6H) ppm.

FT±IR (CCl₄): 2940 (w), 1530 (m), 1480 (s), 1175 (s), 1085

(CDCl₃):

106.7 (t, J 31.7 Hz, 2F),

112.7 (t,

J 9.8 Hz, 2F), 140.7 (m, 2F), 162.8 (d, J 14.6 Hz,

2F) ppm. ¹H NMR (CDCl₃): 7.63±7.53 (m, 5H), 7.26 (s, 1H)

ppm. FT±IR (CCl₄): 3550 (w), 1550 (s), 1500 (s), 1250 (m),

1200 (m), 1010 (m), 980 (m).

4.1.30. 1-(3-Methylphenyl)-2-(4-methoxytetrafluorophenyl)-

tetrafluoroethane

A mixture of 0.29 g (0.8 mmol) of 1-(3-methylphenyl-2-

penta¯uorophenyltetra¯uoroethane and 2 mmol of sodium

methoxide in 10 ml of CH₃OH and 5 ml of ether was stirred

at room temperature for 1 h. After the solvent was evapo-

rated, the residue was diluted with 30 ml of ether, washed

with water and dried over MgSO₄. After evaporation of the

ether, the residue was recrystallized from ethanol to give

0.14 g (47%) of product; ¹⁹F NMR (CDCl₃): 106.7 (t,

J 31.8 Hz, 2F), 112.2 (t, J 10.0 Hz, 2F), 140.7 (m,

(s), 1065 (s), 975 (s); GC±MS: 398 (M , 1.3), 383 (2.3), 356

(10.4), 215 (9.3), 141 (100), 91 (8.4), 43 (14.5), 41 (10.5).

4.1.34. 1-Phenyl-2-(4-phenoxytetrafluorophenyl)-

tetrafluoroethane

1

2F), 157.9 (d, J 14.6 Hz, 2F) ppm. H NMR: 7.38 (m,

A mixture of 0.34 g (1 mmol) of 1-phenyl-2-penta¯uoro-

phenyltetra¯uoroethane and 4 mmol of sodium phenoxide

in 10 ml of ether was stirred at room temperature for 4.5 h.

4H), 4.18 (s, 3H), 2.42 (s, 3H) ppm. GC±MS: 370 (M , 4.1),

229 (21.4), 141 (100), 91 (10.0), 56 (3.2).

102

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

After the solution was evaporated, the residue was diluted

with 30 ml of ether, washed with water and dried over

MgSO₄. After evaporation of the ether, the residue was

recrystallized from hexane to give 0.3 g (72%) of product;

¹⁹F NMR (CDCl₃): 106.8 (t, J 31.8 Hz, 2F), 112.3 (t,

J 9.8 Hz, 2F), 139.1 (m, 2F), 153.3 (d, J 14.7 Hz,

2F) ppm. ¹H NMR (CDCl₃): 7.55±6.96 ppm. FT±IR (CCl₄):

0.30 g (71%) of product; ¹⁹F NMR (CDCl₃): 106.7 (t,

J 31.7 Hz, 2F), 111.9 (t, J 9.8 Hz, 2F), 138.0 (m,

2F), 148.0 (m, 1F), 160.6 (m, 2F) ppm. ¹H NMR

(CDCl₃); 7.77 (s, 1H), 7.38 (m, 2H), 2.48 (s, 3H) ppm.

FT±IR: 1550 (s), 1525 (s), 1215 (m), 1120±1100 (m), 1020

(m); GC±MS: 438 (M , 4.3), 436 (M , 4.1), 219 (100), 221

(97.6), 217 (73.4), 167 (19.7); 140 (51.4), 139 (21.5), 99

(13.1), 89 (12.8), 75 (6.3).

1525 (s), 1409 (s), 1190 (s), 970 (m); GC±MS: 418 (M ,

5.0), 219 (7.4), 127 (100), 77 (19.4).

4.1.38. 1-(4-Methylphenyl)-2-pentafluorophenyl-1,1-

dichloro-2,2-difluoroethane

4.1.35. 1-(2-Nitrophenyl)-

2-(4-hexylaminotetrafluorophenyl)tetrafluoroethane

A mixture of 0.30 g (0.77 mmol) of 1-(2-nitrophenyl)-2-

penta¯uorophenyltetra¯uoroethane and 4 ml of hexylamine

was stirred at 608C for 4 h. The solution was evaporated to

remove excess hexylamine and the residue was diluted with

40 ml of ether and then was washed with 10% HCl, satu-

rated Na₂CO₃solution and dried over MgSO₄. After eva-

poration of the ether, 0.24 g, (66%), of the product was

obtained. ¹⁹F NMR (CDCl₃): 105.1 (t, J 31.8 Hz, 2F),

107.9 (s, 2F), 143.0 (m, 2F), 161.7 (d, J 14.6 Hz,

A mixture of 0.36 g (1 mmol) of 1-(4-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane, 0.16 g (2 mmol) of

acetyl chloride and 2 mmol of TiCl₄in 10 ml of CH₂Cl₂

was stirred at room temperature for 26 h. The solution was

poured into a beaker with 10% HCl, extracted with CH₂Cl₂.

The organic layer was washed with Na₂CO₃solution, dried

over MgSO₄. After evaporation of the CH₂Cl₂, the residue

(0.36 g) was obtained, which was recrystallized from hex-

ane to give 0.25 g (64%) of product; ¹⁹F NMR (CDCl₃):

94.9 (t, J 31.7 Hz, 2F), 134.2 (m, 2F), 148.4 (m,

1F), 160.2 (m, 2F) ppm. ¹H NMR (CDCl₃): 7.61 (d,

J 8.3 Hz, 2H), 7.19 (d, J 8.3 Hz, 2H), 2.40 (s, 3H)

ppm. FT±IR: 1540 (s), 1515 (s), 1265 (w), 1195 (m), 1145

(m), 1115 (s).

1

2F) ppm. H NMR (CDCl₃): 7.69±7.27 (m, 4H), 4.60 (br,

1H), 3.44 (br, 2H), 1.56±1.30 (m, 8H), 0.90 (m, 3H) ppm.

FT±IR: 3420 (w), 3020 (w), 2910 (w), 1650 (m), 1550 (s),

1520 (s), 1250±1220 (m), 1000 (m); GC±MS: 470 (M ,

8.0), 417 (M 1, 2.0), 399 (5.5), 298 (100), 214 (48.5),

192 (20.5).

4.1.39. 1-(2-Methylphenyl)-2-pentafluorophenyl-1,1-

dichloro-2,2-difluoroethane

4.1.36. 1-Phenyl-2-(4-diethylaminotetrafluorophenyl)-

tetrafluorothane

A mixture of 0.36 g (1 mmol) of 1-(2-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane and 2 mmol of TiCl₄in

5 ml of CH₂Cl₂was re¯uxed under Ar for 3 h. The reaction

mixture was poured into 10% HCl solution and extracted

with CH₂Cl₂. The combined organic layers were washed

with water and dried over MgSO₄. After evaporation of the

CH₂Cl₂, 0.38 g of a residue was obtained, which was

puri®ed by recrystallization from hexane to give 0.22 g

(61%) of product; ¹⁹F NMR 93.2 (t, J 31.7 Hz, 2F),

134.0 (m, 2F), 148.0 (m, 1F); 161.1 (m, 2F) ppm. FT±

IR: 1520 (s), 1485 (s), 1185 (w), 1120 (m), 985 (s); GC±MS:

A mixture of 0.34 g (1 mmol) of 1-phenyl-2-penta¯uoro-

phenyltetra¯uoroethane and 6 ml of diethylamine was stir-

red at 608C for 2.5 h. After the solvent was evaporated to

remove excess diethylamine, the residue was diluted with

30 ml of ether, washed with water and dried over MgSO₄.

After evaporation of the ether, a residue (0.6 g) was

obtained, which was recrystallized from hexane to give

0.24 g (60%) of product. ¹⁹F NMR (CDCl₃): 106.6 (t,

J 31.7 Hz, 2F), 112.5 (t, J 9.8 Hz, 2F), 142.0 (m,

1

2F), 150.7 (d, J 12.2 Hz, 2F) ppm. H NMR (CDCl₃):

390 (M , 1.5), 392 (M , 1.1), 394 (M , 0.2), 355 (2.8), 299

(6.0), 173 (100); 175 (64.7), 177 (11.2), 167 (19.2), 103

(29.2), 77 (15.6).

7.56±7.52 (m, 5H), 3.33 (q, J 6.8 Hz, 4H), 1.15 (t,

J 6.8 Hz, 6H) ppm. FT±IR: 3015 (w), 2940 (w), 1590

(s), 1525 (s), 1220 (m), 1120 (m), 1025 (m); GC±MS: 397

(M , 8.0), 382 (27.0), 270 (12.0), 226 (20.2), 214 (7.6), 198

(7.0), 127 (100), 77 (16.6).

4.1.40. 1-(3-Methylphenyl)-2-pentafluorophenyl-1,1-

dichloro-2,2-difluoroethane

A mixture of 0.36 g (1 mmol) of 1-(3-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane and 0.53 g (4 mmol) of

aluminum chloride in 10 ml of CH₂Cl₂was stirred at 788C

for 5 h and then warmed to room temperature. After being

treated with 10% HCl, the reaction mixture was extracted

with CH₂Cl₂. The combined organic layers were washed

with water and dried over MgSO₄. After evaporation of the

CH₂Cl₂, the residue was puri®ed by silica gel chromato-

graphy (hexane:CH₂Cl₂ 20:1) to give 0.24 g (62%) of

product; ¹⁹F NMR: 94.8 (t, J 31.7 Hz, 2F), 134.2 (m,

2F), 148.3 (m, 1F), 161.1 (m, 2F) ppm. ¹H NMR

4.1.37. 1-(3-Bromo-4-methylphenyl)-2-

pentafluorophenyltetrafluoroethane

A mixture of 0.36 g (1 mmol) of 1-(4-methylphenyl)-2-

penta¯uorophenyltetra¯uoroethane, 0.8 g (5 mmol) of Br₂

and 0.06 g (1 mmol) of Fe in 5 ml of CCl₄was stirred at

758C for 5.5 h. The solvent was poured into Na₂SO₃solu-

tion and extracted with CH₂Cl₂. The combined organic

layers were washed with water and dried over MgSO₄.

After evaporation of the solvent, a residue (0.46 g) was

obtained which was recrystallized from ethanol to give

Z.-Y. Yang, D.J. Burton / Journal of Fluorine Chemistry 102 (2000) 89±103

103

[27] Z.-Y. Yang, D.M. Wiemers, D.J. Burton, J. Am. Chem. Soc. 114

(1992) 4402.

(CDCl₃): 7.3±7.24 (m, 4H); 2.39 (s, 3H) ppm. FT±IR 1520

(s), 1495 (s), 1190 (m), 1125 (m), 1000 (s). GC±MS: 394

(M , 0.2), 392 (M , 1.1), 390 (M , 1.5), 357 (0.9), 357

(2.8), 177 (11.2), 175 (64.7), 177 (100), 167 (19.2), 103

(29.2), 77 (15.6).

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Acknowledgements

We thank the National Science Foundation for ®nancial

support of this work.

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Article Doi

A novel double insertion of the difluoromethylene unit from trifluoromethylcopper into the carbon-copper bond of perfluoroaryl- and perfluorovinylcopper reagents: Preparation, mechanism and applications of new fluorinated copper reagents

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