Configurational assignment of oxymercurials by nmr

Tetrahedron Letter8!bo.42, PP 4327 - 4330,1972. PergamonPrefm.

CONFIGURATIONAL Robert F. Department

ASSIGNMENT

Richter,

Department

The oxymercuration

1972; received

of simple

unstrained

olefins

hydroxymercurials reported

has been reported.

by Traylor.

for determining deshielding

7a

More

recently,

the configuration

Detroit,

proceeds

3 bicyclo[2.

stretching

Waterstb

Michigan Michigan

48202 48221

19 September1972)

by a trans addition.

2

However,

1. l]hexene4

With bicyclo[

frequency

has reported

and trans-cyclo6both cis and 2. 2. 21 octene the cis/trans

in the infrared

ratio of has been

a convenient nmr method

This method is based upon a

of methoxymercurials.

effect of a methoxyl

Detroit,

A method for determining

based upon the hydroxyl

BY NMR

and Robert D. Bach’

in IlII for publication

with highly reactive olefins such as norbornene, 5 octene, cis oxymercuration has been observed. trans oxymercuration

Philips

Wayne State University, and University of Detroit,

of Chemistry,

(Received in USA 17 &ust

OF OXYMERCURIALS

J. Christopher

of Chemistry,

Printed in Ge*tBritaln.

group when it is cis to the HgX moiety

field shift.

We now report an nmr method for establishing

mercurial8

and an alternate

nmr method for determining

resulting

the cis/trans

in a down-

ratios of acetoxy-

the configuration

of methoxy-

mercurials. Our experimental methanol chloride

solvent.

Saturated

is extracted

solution and saturated the nmr spectrum

procedure

involves

of the oxymercurial

is measured

of the oxymercurial assignment

However,

in acetic

acid or

solution is added and the mercuri-

with CH Cl The CH2C12 is washed with water, sodium bicarbonate 2 2’ sodium chloride. The CH2C12 is removed under reduced pressure and

of our configurational mercurial

the oxymercurial

aqueous sodium chloride

and the nmr spectrum

mercurial6

preparing

in CC14 solvent

versus

exhibit an aromatic in the examples

rests

is then measured

upon the difference

pyridine

solvent

in CC14 solvent.

solvent

(Av

in pyridine in chemical

solvent).

induced upfield chemical

studied the chemical

shift difference

4327

The CC14 is removed solvent.

The basis

shift of an oxy-

Both cis and trans oxyshift in pyridine

solvent.

for both acetoxymercurials

m.

4320

and methoxymercurials

is consistently

The chemiaal

shifts

of the methoxy

superposition

of the appropriate

audiooccilator.

The results

Our data also provide chemical

shift difference

solvent

(A Y OCH3). ’

However,

(e. g.

resonance

, cyclohexene)

a definite

with olefins

octene) for comparison The reasons

with more

trans-acetoxymercurials

derived

of I. 4,

readily

solvent

by only 3.6

pyridine

to the mercury.

of the relatively resulted

resonances

in Ccl4

supposition

However,

1.6,

solvent

9

In pyridine

and a separation

i. 8 and 2. 0 Hz,

and

However,

per equivalent

solvent,

in pyridine

of acetoxy-

of the acetoxy

peaks

the acetoxy peaks were

the ratio of cis and trans isomers

of pyridine

acetoxymercurials

suggested

can be

that the difference

was due in part to coordination inclusion

of the acetoxy from

a similar

of pyridine

resonances series

respectively.

of one or two equivalents

on these acetoxymercurials

derived

1

resonance

for

from

i is due to a ligand

in benzene

resonances

solvent,

An

of 9. 8 Hz was

Inclusion

of the acetoxy

(268-296OK)

from

of the acetoxy

the methyl

were not resolved.

temperature

of the

support for the

derived

in a separation

in

Further

of experiments

shift of the acetoxy

resulted ii

out a variable

of 2, 6-Lutidine

on the cis resonance.

the cis and trans resonances

We have also carried

to make

olefin (i-

using an expanded sweep width spectrum.

solvent induced upfield chemical

observed.

shift

With four equivalents

comes

three and four equivalents 1. I,

in an upfield

as a shoulder

that the separation

in order

shift for the -cis-

Hz in CH2C12 solvent.

of pyridine

In support of this suggestion,

solvent.

effect on the mercury aromatic

in chemical

2,6_dimethylpyridine to the acetoxymercurials 10 but did not cause a measurable separation shift

appeared

ether in CC14

In those cases

for oxymercurials

hindered

in an upfield

the trans isomer

i is only 0.4

of minor amounts

shift of the isomeric

shifts.

should be examined

The difference

respectively.

obtained by integration

chemical

shift differences

In both experiments

Hz.

The marked influence chemical

from

resulted

2. 3, 2. 8 and 3. 1 Hz,

separated

identical

two, three and four equivalents

in Ccl,

methyl

2 and 5 are in good accord with Waters data. 7b _ _ oxymercurials where the alkoxy group is not

oxymercurials

chemical

and intriguing.

mercurial

based upon the

rigid oxymercurials.

for the observed

of one,

using an

We have also included data for an acyclic

solvent are both complex

inclusion

assignments

and its corresponding

have nearly

assignment.

to TMS by

are given in Table I. of configurational

that isomeric

both of the isomeric

configurational

relative

with the side band of TMS generated

examples

environment

than for the trans isomer.

groups were measured

of the methoxymercurial

The results

different

for the cis isomer

of our experiments

additional

it should be emphasized

in a distinctly

greater

and acetoxy

42

of one,

two,

resonances

nmr study in toluene

in the hope of shifting the equilibrium

in favor of acetoxy-

I

I

/

’

7

c

6

5

f

3

2

.?_

trans trans

trans trans

==‘,t”, -

trans

;p”

cis

zl;ps -exe-trans

-exo-cis

cis trans cis trans

Producta

t

C5H5N

ccl,

C5H5N

CC14

C5H5N

cc14

C5H5N

cc14

C5H5N

C5H5N

cc14 cc14

C5H5N

E;b5N

cc14

C5H5N C5H5N

cc14 cc14

Solvent

199.7 196.0

195. 2 191.2

196. 3 194. I

203. I 191.4

201.2 201.2 192.7 193.4

198. 8 193.2 192.8 189.7

201.0 198. I 188.2 192.4

192.7 194.6

187.0 187.4

189. 3 191.4

190.2 190.3

194.0 194.0 194.3 194.3

189. 0 I86.8 190.7 186.9

192. 7 192.7 192.4 192.4

Methyl etherC

121. 8 115. 8

I20.9 116.4

121. 6 115. I

116.1

122.7

120.8 120.8 115.8 1\17.9

122.9 122.9 113.4 117.5

Acetoxy Mercurial

115.9 117.0

116.4 118. 0

115.3 116.1

118. 0

117.6

116. 7 116. 7 117.1 117.7

117.3 117.3 119. I 119.1

Acetated

I

2 2 6 9

7. 0 1.4

8. 2 3. 8

7. 0 2. 7

12.9 I. I

7. 7. -1. -0.

9. 8 6.4 2. I 2. 8

8. 3 5.4 -4. 2 0. 0

AuOCH;

5. 9 -I. 2

4.5 -1. 6

6. 3 -1.0

-1.9

5. 1

0. 2

4. 1 4. I -1.3

5.6 5. 6 -5. 7 -1. 6

8 AK-CH;

3. 7

4. 0

2. 2

11.7

8. 5 7. 8

6. 0 3. 5

12. 8 5. 7

OMe

6. 0

4.5

6. 5

6. 6

5. 0 2. 9

9. 5 5.4

R C-CH3

Au Solventg

-

-

~. ._

-

-

-

-

-

-

-

b ‘Methyl ether obtained by NaBH4 reduction of the aExo mercury sqbstitutent. All values are in Hz relative to TMS. oxymercurial. “Alkyl acetate obtained by NaBH4 reduction of the oxymercurial. “Frequency of the methoxymercurial minus the frequency of the methyl ether. fFrequency of the acetoxymercurial minus the frequency of the alkyl acetate. SFrequency of the oxymercurial in Ccl4 minus its frequency in pyridine solvent.

1-octene

o-

&

0

d3

Olefin

Methoxy Mercurialb

TABLE

-

3 .

5 Q

w

P

mercurial-solvent the assumptions + toluene

complex described

i? complex,

to enhance the solvent shifts. We used the method and 12 that the equilibrium, acetoxymercurial

and Williams

is driven toward complex

Using CC14 as the “inert” complex

formation by Laszlo

solvent,

plots of log K s

between -cis-acetoxymercurial

the hrans isomer

was measured

formation

of the solvent

However.

in pyridine

correlation

between temperature

as well as,

an aromatic

Acknowledgments.

Grant No.

as -0.87

f

Chemical

In pyridine

acetoxymercurials

of the I:1 The AH for

. 08 kcal/mole. solvent

2. 2. 2Joctane was -3. 7 I 0.7

the AH of

kcal/mole.

did not exhibit a linear

These data support the above suggestion that the eq’ is due to coordination of pyridine with the mercury,

solvent induced chemical

shift.

We wish to thank the Petroleum

ES 00761-01,

i

and K

resonances

Society,

in temperature.

gave a heat of formation

. 08 kcal/mole.

with 2-acetoxybicyclo[

of the acetoxy

I/T

with a decrease

and toluene as -0.94

solvent the above isomeric

separation

the American

formation

Grant No.

Research

Fund,

administered

1829 G3, and the National Institutes

by

of Health,

for support of this work. References

I.

Author

2.

W.

3.

(a) (b)

4.

F.

5.

V. l. Sokolov, i36 (1966).

6.

T. E.

7.

(a) (b)

8.

9.

to whom inquiries

Kitching, T. R. T.

Organometal.

should be addressed Chem.

Rev.,

at Wayne State University.

3, 61 (1968).

G. Traylor and A. W. Baker, Tetrahedron Lett., D. Bach and R. F. Richter, ibid., 3915 (1971). Bond,

J. Amer. L.

L.

Chem.

T. G. Traylor W. L. Waters,

Chem.

90, 5326 (1968). and 0. A. Reutov, Dokl.

19,

p. 14,

1959.

Sot.,

Troitskaya

G. Traylor, J. Amer. , 94, 4747 (1972).

No.

Sot.,

86, -

244 (1964);

Akad.

Nauk SSSR,

R. D. Bach and R. F.

116, Richter,

and A. W. Baker, 3, 85, 2746 (1963). Tetrahedron Lett., 3769v969).

7b The slight differences in AU OCH3 in Ccl4 from those reported by Waters are most likely due to different experimental procedures. We have observed that the methoxyl resonance of 2-methoxybicyclo[2. 2. 2]octane was shifted upfield by 0. 5 Ha in the presence of one equivalent of a mixture of cis and trans methoxymercurials derived from 1. The resonances of the methoxymercurials were unchanged. The chemical shift of the cis isomer was 120.6, 1 IS. 8, 117.4 and 116. 5 He, while the chemical shift of the trans isomer was 121.9, 121. 1, 120. 2 and 119. 5 Hz, respectively.

IO.

The chemical shift of both isomers were 122. 0. two and four equivalents of 2,6-Lutidine.

II.

The chemical shift for the cis and traus isomer is 113. I Hz in benzene. With four equivalents of pyridine the chemical shirt of the cis isomer was 113. 5 and the trans isomer I I I. 6 Ha.

I 2.

P. Laszlo

and D. H. Williams,

J. Amer.

Chem.

121. I and 120. 8 with addition of one,

Sot.,

88. 2799 (1966).