Selective oxidations with ceric methanesulfonate and ceric trifluoromethanesulfonate

Tetrahedron Letters,Vol.28,No.lO,pp Printed in Great Britain

SELECTIVE

OXIDATIONS

AND CERIC

Robert W. R. Grace

P. Kreh:

& Company,

0040-4039/87 $3.00 + -00 Pergamon Journals Ltd.

1067-1068,1987

WITH

CERIC

METHANESULFONATE

TRIFLUOROMETHANESULFONATE

M. Spotnitz

Robert

Washington

Research

and Joseph

Center,

T. Lundquist

Columbia,

21044

Maryland

Cerium(IV) in aqueous methanesulfonic acid and trifluoroSummary. methanesulfonic acid are excellent reagents for the oxidation of alkyl and polycyclic aromatics to aromatic aldehydes, ketones and quinones. The ceric agent

ion has been

in the synthesis

and quinones cerium(IV)

from polycyclic

have

known

for some time to be a selective

oxidizing

of aromatic

greatly

aldehydes and ketones from alkyl aromatics aromatics. 1,2 However, the anions used with

limited

its usefulness

due to instability

toward

oxidation

(e.g., chloride3), undesired reactivity with the organic substrates 1,4 chloride, 3 , perchlorate5) nitrate, or marginal solubility and slow (e.g., 8 6,7 organic oxidations (e.g., sulfate, acetate, trifluoroacetate'). We have found

that cerium

obviate

the above

substrates with

of methanesulfonate

problems,

give high

(Table I) and are easily

high

efficiency

are fast under products

salts

at high

conditions

are immiscible

separation.

In these

the cerium

respects,

for a wide

Also,

salts

making

superior

oxidations

and the organic

for facile

product

and ceric

to Cr(VI),l'

electrochemical

of

oxidation

the organic

are soluble

solutions,

ceric methanesulfonate

trifluoromethanesulfonate are clearly l-7,9 Ce(IV) reagents and direct

range

by electrochemical

densities.

the aqueous

known

Table I.

selectivities

recycled

current

where with

and trifluoromethanesulfonate

Mn(III),ll 12

other

oxidation.

Oxidations with Ce(IV) in Methanesulfonic Acid and TrifluoromethanedulfonicAcid

Substrate toluene toluene

Cont. CH3S03H(M)

Temp. ("C)

Reaction Time (min)

Products

Yield Based on Substrate

5.5

80

10

benzaldehyde

91 75

2.4a

25

40

benzaldehyde

5.5

60

10

m-tolualdehyde

70

5.5

80

15

p-chlorobenzaldehyde

86

ethylbenzene

5.5

80

13

acetophenone

44

naphthaleneb b anthracene

2.5

60

35

1,4-naphthoquinone

89

5.0

25

4

9,10-anthraquinone

95

m-xylene p-chlorotoluene

p-methylanisolec 3.6 5 40 p-anisaldehyde 71 b aCF3S03H used in place of CH3S03H. Substrate diluted 1:20 with 1,2_dichloroethanebefore addition. 'Aqueous solution diluted 1:2 with methanol prior to substrate addition.13

1067

1068

Preparation carbonate with

of Cerium(IV)

Solutions:

in 160 ml of water,

CO2 evolution,

resulting 14

(Ce(CH3S03)3'2H20) introduced

in 0.6M cerous

and 6M methanesulfonic

into the anolyte

compartment

ce11.15

The anode was platinum-clad

surfaces

coated

with

The anolyte

commercial

perfluorinated

was heated

at 50°C while

molar

The resultant

(current

stainless gas.

ion exchange

orange

cathode

The preparation

Oxidation

having

(total surface

both area of ca.

(6M CH3S03H)

(Nafion

had a Ce(IV)

The catholyte

Procedure:

electrolytic

cell was

g, 0.03 moles)

390)

by a

(area=50

cm2)

of 0.53

contained

of protons

and

for 22

concentration

compartment

reduction

in aqueous

minutes.

The resultant chloride.

quantitatively

The above

stirred

methylene

a

C

to hydrogen

trifluoromethanesulfonic

colorless

Acknowledgement: V. R. Hoover

at 80°C under

acid was

were

dried

(dodecane

with

results

a nitrogen

atmosphere. for 10

with

3 x 170 ml of

(MgS04)

and analyzed

internal

standard)

to benzaldehyde.

identical

We thank G. W. Ambrose-Ritchey,

and D. S. McFarland

from the

was continued

was extracted

extracts

and 92% selectivity

was re-electrolyzed

(320 ml)

and stirring

mixture

The combined

of toluene

solution

vigorously

was added

by gas chromatography

conversion

solution

mesh

(320 ml) was

type electrolytic

of 14 amps was passed

a clean

dropwise,

to the above.

Toluene(2.77

98.5%

solution

of Ce(IV)

solution

and frame

expanded

membrane

current

and caused

This

of a plate

from the catholyte

a constant

of 53g of cerous

acid was added

methanesulfonate

of platinum

separated

efficiency=88%).

steel

analogous General

was

suspension

acid.

niobium

63.5 micrometers

240 cm2).

minutes.

To a stirred

240g of methanesulfonic

for technical

to those

showing The Ce(II1)

described

J. B. Davis,

above.

W. L. Henry,

assistance.

References 1. L. Syper,

Tet. Lett.,

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4493 347

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P. M. Robertson,

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