Complex bases. XIV. Use of sodamide containing complex bases as versatile, inexpensive reagents to generate carbanions

Tetrahedron Letters,Vol.25,No.l5,pp Printed in Great Britain

COMPLEX

BASES.

XIV. USE OF SODAFlIDE CONTAINING

AS VERSATILE,INEXPENSIVE

M.C. CARRE, Laboratoire

G. NDEBEKA,

REAGENTS

A. RIONDEL,

P. BOURGASSER

BP 239, 54506 VANDOEUVRE-LES-NANCY

aprotic

solvents

used are lithium

to be of interest'.

reagents

and only a few sodium

derivatives

is a lack of sodium

Some years basic properties enolates Bases

may be preferred

ago, we discovered

de Nancy

I

(France)

with strong

counterparts

exist.

to those of lithium2

salts3.

the concept

modified

basic reagents

Taking

in

bases

into account

it is clear that

h:!dride4 and to lithium or potassium

The new bases thus obtained

were extended 3b,5 amides .

C.B. have been used to perform

the proton

the generation

sodium

were called

to the activation

elimination-additions,

5,6,7 . Concerning

that C.B. were able to abstract 5a,3b substrates .

of bases synergy.

by sodium alkoxides,

C.B.) and the results

polynerisations

and P. CAUBERE*

In this area, the most widespread

and developed

may be strongly

as well as by inorganic

as anionic

BASES

CARBANIONS

basic reagents.

of sodamide

(abbreviated

Cedex

by proton abstraction

continues

that organosodium there

of carbanions

COMPLEX

TO GENERATE

I, ERA CNRS No 476, Universite

de Chimie Organique

Generation

0040-4039/84 $3.00 + .OO 81984 Pergamon Press Ltd.

1551-1554,1984

from tri- and diphenylmethane8

Connlex

of sodium

syn-eliminations

of carbanions,

The

ketone

as well

we first showed and from a few

other

In the present possibilities and they merit

offered

the following

From experiments alkoxides tertiary

paper we wish to describe

by C.B. The main results

(activating alkoxides

examples

have been summarized

of the

in the Table

comments.

not reported,

agents)

some representative

obtained

capable

and diethylene

it appeared

of activating

glycol monoalkyl

1551

that from among the numerous 5a sodamide , the best are found among

ethers.

1552

To obtain good results, emphasized

that, as observed

interfere

with the carbanionic

the condensation

selectively

Generally described

with tri- or diohenylmethane8, condensation

of ketones

unreacted

even with base-sensitive

takes place with the generated

the results

with more sophisticated

sulfenylation data2".

soeaking

excess of C.B. must be used. However

obtained

Indeed C.B. give comparable

of thioketals

demonstrative

or better yields

C.B. does not electrophiles

and

carbanion.

with C.B. compare

bases. Alkylation

are particularly

it should be

favorably

or acetals

if compared

with those and methyl-

with literatuna

and allow simpler experimental

conditions.

Finally,

these reactions

are very easy to perform as exemplified

ration of 2-methylthiocyclohexanone (450 mmol)

: To a mechanically

in THF (50 ml), under a nitrogen

atmosphere,

(150 mmol)

in THF (20 ml) and the mixture

(100 mmol)

in THF (20 ml) was then added dropwise

stirred

for 2 h. After cooling

slowly added classical

work-up,

susnension

was added dropwise

by the preoaof NaNH2 Et(OCH2CH2)20H

was heated at 45°C for 2 h. Cyclohexanone

to O'C, dimethyl

(0.5 h) and the reaction

stirred

at room temnerature

disllfide

(100 nmol)

and the mixture in THF (10 ml) was

was complete

the product was distilled

12.98 g (90 %) of 2-methylthiocyclohexanone

at the end of the addition. After 9b at 85"C/7 mm (Lit. : 83-84'C/7 mm) to yield

which had spectra

identical

with those reported

elsewhere.

In conclusion, with a sodium cation.

C.B. allow the generation

Floreover, very easily

which are less sensitive

to air and moisture

of a number of carbanions

prepared

from commercial

and less expensive

associated

starting

than lithium

materials reagents,

they allov large scale preparation.

Note that by removing

the solvent

from a C.B., Solid Complex Bases are obtained 3b,7a or in an inert adjuvant such as

and may be kept as such under an inert atmosphere mineral

oil and used (after washing)

therefore

be as easily

handled

by simple addition

as any water-sensitive

of a suitable

solid reagent.

solvent.

C.B. may

DME (501

NaNH2-Et[OCH CH 1 ONa (4012 2 2 [601

al After hydrolysis bl In mixture with 10 % of unreacted

(201

OVE (501

NaNH2-Et(OCH2CH2120Na (1201 (601

CH2(SEt12 (201

starting

DrlE[501

NaNH2-Et(OCH CH 1 (301 * 2 2 [60)

THF (501 THFI501 ONaorOME(501

THF (1001

C6H5CH[SEt12 [20)

(30+R+t,Bul

NaNH2-Et(OCH CH 1 ONa (751 137 2 2 _. 512

160)

[IDO)

THF

THF [lOOI

[mll

Solvent

I-Eienzosuberone [251

I-Tetralone

Et2C0

!NaNH2-Et[OCH2CH2120Na (1501 (1001 (300)

1=2,3,4,5

or

NaNH2-RIOCH2CH2120Na

NaNH2-ButONa (301 (601

NaNH2-Et(OCH CH 1 ONa [3012 2 2 (601

C6Hll

Pr-CH=N-I [ZOI

Complex Base CmM of constituentsl

ímmI

Substrate

5

3

5

25

material

-30

Ph-CH2Cl

Me1

(401

Me-S-S-Me 1251

Me-S-S-Me (1001

CH2=CH-CH2Br (201

Ph-CH2Cl (20)

determined

RBr (401 R=Et,C6H13

0

0

0

hy 1H NMRI.

[401

(401

CôH13Br

Me1

2

0

0

o-5

-35

-30

(OCl

[mMI 120:

Condensation temperature

Condensed electrophile

RBr [401 R=Et~cr;PhCH21

(ratio

3

3

25

25

2

2

2

2

2

25

25

25

0

25

25 2 [n=3,4,51

60

50

Preparation of carbanion T('CI t(hl

n=4

(701

(701

(701

[761;

R

162);

R=Et

[661

(62);

C6H13

(061

[721

(661

(901

(801

n=5

n=3

.-

Itrap-es1

PhCH2(861;@CH2

(60-851

[701b1

iPr

[C6H13)CH[SEt12

NeCH[SEt12

R=Et

C6H5[RlC(SEt12

We(C6H5)C(SEt12

__-

----

Oisubstituted

"SI

Oisubstituted (traces)

2-Methylthio-1-benzosuberone

2-Methylthio-1-tetralone

Me(MeSlCH-CO-Et

O

n=2

(641

MeCTCH2-PhlTPrlCHO

CH2 R= L//L351a1

al

[SSI

0

R=CH2Ph

Me2C(CH2-PhlCHO

R

yield 1551al

(601

[isolated

Ph-CH2-CH[EtlCHO

Product

(76

1554

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