A novel synthesis of diaryl ethers

Tetrahedron

Letters

No.4,

PP. 409-411,

1968.

Printed

Pergamon Press.

in Great Britain.

A NOVEL SYNTHESIS OF DIARYL ETHERS Herbert

Meislich,

Arnold Speert and Miriam

Department The City College

of Chemistry

of The City University

New York, (Received The reactions several

silver

salts

in a variety between

cation

attempted

synthetic

acid

cent

was

shown

analysis

may signal

silver

in benzene)

or aryl)

with

laboratories

to look

at Cd and migration

(I)

reports

(1)

with

silver

the isolation

the importance

of an

One of several

of a phenol.

signal

at 5.12

D,O),

and changes

6

perchlorate

84.65

and identifi-

of this reaction

as a

is very similar

element

is also

and 8.74

identical

On the basis

of this evidence

bis-3,4,5_trimethylphenyl

ether,

III.

6

hydrogen.

If the

formula

and H-8.72

percent.

for the absence

of The

of a peak at

and for the presence

of a peak at 1175 cm-‘.

to that of II, except

for the absence

in the chemical

the neutral The mass

m .p. from acetone.

an empirical

, owing to the OH group (lost when the solution of no more than 0.05

overnight

to a 38.1 per-

fraction,

percent

C-84.99

to that of II, except

practically

amounting

A neutral

is oxygen,

are:

to the OH stretching,

was continued

fraction

(II).

over concentrated

after one recrystallization

carbon

values

in vacua

benzene

An acidic

yield

percent

The calculated

(dried

in anhydrous

in 37 percent

was

corresponding

The NMR spectrum

peaks.

which

is made that the remaining

spectrum

3610 cm-’

in these

of 4-bromoisophorone

to be 3,4,5_trimethylphenol

CisHzzO is obtained. infrared

studied

or solvent

precursor

from light and moisture.

was isolated

The elementary assumption

product

(R=alkyl

This communication

benzene.

and azeotroped

protected

yield

is being

by anion

the intermediate

of I with anhydrous

in a flask

145-145.5OC,

1957)

method.

The reaction sulfuric

of solvents

was the reaction

in anhydrous

of an unexpected

broad

10031

in USA 21 February

displacement

R group from C, to C., giving

porchlorate

N.Y.

of New York

of 5,5-di-R-4-bromo-2-cyclohexene-l-ones

at the competition

experiments

Blejwas

fraction spectral

of II was

shifts

analysis

shaken

of the remaining

was assigned was

of a with three

the structure confirmatory

as

follows: a)

the parent peak is at m/e

b)

the ratio

c)

the second

= 254.

of the M and M+2 peak is consistent most

trimethylphenyl

intense

band is at m/e

= 119,

ion.

409

with the molecular indicating

formula

the presence

CrsHszO.

of the

No.4

410

d)

a low intensity peak is observed at m/e = 135, indicating a trimethylphenoxy fragment (2).

e)

the presence of a symmetrical molecule containing three CHs groups on one side is indicated by the appearance of peaks at m/e of 239, 224 and 209. As evidenced

by the ultraviolet,

crude neutral fraction,

infrared and nuclear magnetic resonance spectra of the

some x

-unsaturated ketonic material was present. This + material, which may consist of the 4-hydroxy- and/or the 4-perchlorato-derivatives of isophorone,

was not identified.

The mechanism of the formation of III could involve the reaction of two moles of preformed phenol, or, more likely,

involve the reaction of one mole of pre-formed phenol and

one mole of bromocyclohexenone

.

That the former mechanism is not operative was

demonstrated by duplicating the conditions but in the absence of I.

of the reaction in the presence of the phenol II,

Thus, under anhydrous conditions,

a solution of II in benzene and

a solution of hydrogen bromide in benzene were added over a period of several hours to a solution of silver perchlorate in benzene. several hours with all the possible silver bromide.

In this way the phenol was in contact for

catalysts,

namely, silver ion, perchloric acid and

No ether was isolated.

A plausible mechanism is shown in Chart I. CHART I

b.-_ I

H+,

II

-Hz0

IV Ok

Ar = 3,4,5-(

$

CHI)&.H2

OAr

)

J$

411

No.4

The important

intermediate

tion,

of bromide

b) loss

give the diary1 ether, possibly

precede

is the hemiketal c)

ion,

III.

Loss

a 1,2-methyl

of bromide

isolation

of 3,4,5-trimethylanisole (3),

and from the reaction

methanol

(4).

The major difference is involved

Diary1 ethers type reaction. encouraged modified

These

start of the reaction.

ion and rearrangement

to eventually

of a methyl

is akin to the one proposed of isophorone

group could by Fort for the

with cupric

bromide chloride

is the fact

reactions,

that in Fort’s

of a hemiketal

are being

conditions

of an Ullman-

of the halocyclohexenone

synthesized

experiments

by adding will

is being

other phenols

be reported

at the

later in the complete

paper. Acknowledsment The authors assistance Company sample

wish

to thank the NSF Undergraduate

to two of us (A.S. for the mass

spectral

and M.B.), analysis,

Dr.

Research

R. S. Gohlke,

and Professor

Participation formerly

Marshall

Program for

of Dow Chemical

Beringer

for an authentic

of 3,4,5_trimethylphenol.

References 1) 2)

A.J.B.

Edgar,

Fragmentation

S. H. Harper and M.A. of diphenyl

CbHs+ ion with very little 3)

A.W.

Fort, ---J. Org.

4)

A.W.

Fort,

Lbs.,

Chem., 26,

Kazi,

ether in a mass CbHsO+ ion. &,

332 (1961).

J. Chem.

spectrometer

J.M . Wilson,

765 (1961).

in

rather

of a diary1 ether under such mild conditions The structure

successful

methanol

in

intermediate.

under the very vigorous

synthesis

diary1 ethers

d) aromatization,

with dry hydrogen

synthesized

The unexpected

a) dehydra-

undergoes

of 6-tosyloxyisophorone

a study of its universality. and mixed

and

from the reaction

in formation

are normally

in sequence

shift,

This mechanism

dehydration.

methanol

than a phenol

IV, which

Sot., gives

1083 (1957) predominantly

Experentia,

-16.

403

the

( 1960).