The oxidation of silanes in dimethyl sulfoxide

Tetrahedron Letters ~0.46, Printed in Great Britain.

THE

pp.

3449-3452,

OXIDATION DIMETHY

Robert

and Douglas

of Chemistry,

The

strong

bases,

of studying

the behavior

we have found that di-

compounds.

The

sulfide

is evolved

taining

compounds

the relative

base

of dimethyl

reaction

concentrations

Methyldiphenylsilane sulfoxide

containing

at room

temperature,

mixture

was worked

Dilute

aqueous

up 10 minutes

with ether.

indicated

that the starting stretching

at 5.07

of the starting

sulfoxide

sulfide

frequency material

was absent.

anion, The

*

reacts

reaction

of the silane.

of the product completely

The absence the above

of

of dimethyl

sulfoxide

the addition

con-

ankx~ and the silane.

solution

had reacted

confirmed

Dirnethyl

are functions

is evolved.

red spectrum

material

silicon

Both the type of silicon sulfide

of

react

oxygenated

and quantitative.

of dimethyl

after

silanes

acid was added and the organic

An infra

4.7pSi-H

rapid

1964)

in the presence

to yield

when added toa

and dimethyl

extracted

sulfoxidee

of dimethyl

one equivalent

hydrochloric

of silanes

of the dimethyl (I),

University

form 5 October

product.

and the amount

Marks

and trisubstituted

is extremely

as the reduced

L.

Ohio

in revised

with the conjugate

IN

Ohio State

15 June 1964;

In the course

Ltd.

L SULFOXIDE

Columbus, (Received

Pergamon Press

OF SILANES

J. Ouellette

Department

1964.

materials mixture as the

of the quartet

observation.

The

The conjugate base of dimethyl sulfoxide was produced utilizing sodium hydride. The required quantity of a 56$sodium hydride-mineral oil dispersion was washed three times with pentane to remove the mineral oil. The final traces of pentane were removed by a stream of nitrogen. Freshly distilled dimethyl sulfoxide was added to the sodium hydride. After heating at 600 for one half hour, the clear solution was cooled to All reactions were carried out room temperature and used immediately. under a nitrogen atmosphere.

3449

3450

No. 46

reaction

product

consisted

of a mixture

bis-(m&h)-ldiphenyl)-siloxane performed

utilizing

of methyldiphenylsilanol

(III) in the ratio

the intensities

of 4.3

of the methyl

to 1.

singlets

(II) and

Analysis

(n. m. r.)

was of

each compound. Ph

Ph

Ph

I

I

I

CH,-S

t-H

I

I

Ph

I

II

That the oxygenated up was

confirmed

zation.

Vacuum

containing identical

products

by utilizing transfer

compounds products

The product sulfoxide

anion and silane.

dimethyl

sc.lfoxide

product

the latter

indicating

bromide

in ether

in the aqueous

of the relative

The

sulfoxide

silane

was

that only a catalytic

work

for neutraliof silicon

yielded

the

work up.

amounts

excess

only the silanol

of the dimethyl

the aqueous

and dissolution

residue

When a two-fold

was the siloxane.

case

sulfoxide

observed

from

hydrogen

the resultant

was employed,

one tenth ol’ an equivalent sole

are not derived

is a function

I

Ph III

anhydrous

that were ratio

I

Ph

of dimethyl

from

1

CH3-Si-0-Si-CH,

CHs-Si-OH

PI

Ph

of dimethyl

of the anion of was obtained.

When

anion was used,

completely quantity

the

consumed

of base

in

is required

for the reaction. Methylzliphenylsilane of the dime,:hyl species silicon in order

sulfoxide

is stable anion.

is the anion of dimethyl atom.

However

to allow

It is therefore sulfoxide

the dimethyl

the reaction

of the anion is less

to dimethyl

to occur

than stoichimetric.

sulfoxide likely

in the absence

that the attacking

which transfers

sulfoxide

anion must

quantitatively The relative

oxygen

to the

be regenerated

when the concentration yields

of silanol

and

3451

NO.26

siloxane attack

can be rationalized

as the siloxane

of the anion of the silanol

concentration following

is sufficiently

reaction

sequence

undoubtedly

on unreacted

silane

low to allow

competition

is proposed

to explain

results

from

when the base to occur.

The

the observed

products.

0

Ph 1.)

I

Ph-Si-H

7

t

CHati-CH,

9”@

__$

Ph-Si-0

CH3

Ph 2.)

CH,S CH3

t

\

\ CH, 1 0

Ph-Si-0

t

0

Ph

I

I

CH,-S-CH,

00

Ph-SiOH

&

I

cY,=S

t

-CH,

I

I CH3

CH3

Ph 3.)

I

Ph-Si-0

0

t

I

0

4.)H

t

In order pathway

I

CH,-S-CH,

to provide

the following

silane

with the same

sulfoxide. system contents sulfide

sulfoxide

The yield with nitrogen

supporting

facility

t

evidence

H,

for the proposed

experiments

of the sodium

produced

were

salt

carried

that oxidized

as a solution

containing

and trapping warmed

manometrically.

sulfide

to 50’

Addition

the anion of dimethyl

material

and the yield

In two

out.

methyldiphenyl-

was determined

condensable

oxidation

of methyldiphenylsilanol

a solution

of dimethyl

of the trap were determined

CH,-S=CH2

additional

of a tenth of an equivalent to dimethyl

I

j

by sweeping at -78’.

the

The

of dimethyl

experiments

utilizing

three

3452

No.46

equivalem:s

of the conjugate

equivalen:s

of dimethyl

quantities

dicted

of dimethyl

quantities

one equivalent

sulfide

were sulfide

Utilizing

0.42

and 0.47 The

nt with those

At high base

is predicted

and 0.89

catalytic

in two trials.

are in agreene

one half equivalent

0.81

sulfoxide

produced

scheme.

sulfide

s&oxide,

obtained.

of dimethyl

oxidative

of dimethyl

of base

of dimethyl

were

base

of dimethyl

by the proposed

quantities

sulfide

of the conjugate

equivalents served

base

obpre-

concentrations

whereas

with catalytic

of dimethyl

sulfide

the oxidation

step

should

be

produced. The been

exact mechanism

established.

simultaneous

However,

transfer

Diphenylsilane conditions tetrasiloxane

where

by which

a reasonable

of oxygen

also

is produced

and hydrogen

undergoes

an equivalent

cyclic

mechanism,

occurs,

the oxidation

of base

and dimethyl

is employed. sulfide

occurs

has not in which

can be written.

reaction

under

Octaphenylcyclo-

is evolved.