Stereoselective synthesis and reactions of 1-seleno-4-tert-butyl cyclohexyllithiums

Tetrahedron Printed in

Letters,Vol.30,No.41,pp Great Britain

Stereoselective

Synthesis

5635-5638,1989

and Reactions

0040-4039/89 $3.00 Pergamon Press plc

of 1-Seleno-4-tert-Butyl

+ .OO

Cyclohexyllithiums

A. KrieP, G. Evrard*, E. Badaoui, V. De Beys and R. Dieden Department

of Chemistry,

Facult& Universitaires

Notre-Dame

de la Paix, 61 me de Bruxelles,

B-5000 Namur (BELGIUM) The axial C-Se bond of seleno- and mixed selenoacetak derivedfrom I-tert-butyl cyc2ohexanones exhibit

a high tendency to be cleaved by n-butyllithium. The resulting 1 -selerw+tert-butyl

cyclohexyllithium

are selective& protonated or seIenyIated via axial attack.

We recently described 1 that l,l-bis@henylseleno)4tert-butyl to provide, complete

after hydrolysis, stereocontrol

intermediarily phenylseleno

I-(phenylseleno)-4-tert-butyl

(Scheme

1 entry I). Although

formed 1-lithio-4-tert-butyl

cyclohexane

delivers the corresponding have

for

that

and have directly

phenylseleno

performed

the crude

the perdeuterated

methylseleno-4-tert-butyl

cyclohexane

I-methylseleno-

u

substituted

of the

in the axial position,

an axial carbon lithium bond.

reaction

of selenides

group and

on

l-phenylseleno-l-

by GCMS

moiety in the axial 2. We found

moiety whereas the perdeuterophenyl

group becomes

moiety

in the axial position

leads

to similar

cyclohexane results

&’

since

l-

substituent

is

on this spectacular

behaviour

we looked at the reactivity

cyclohexanes

4 that this reagent usually cleaves selectively and a methylseleno to possess

group providing

the more stabilised

tram l-phenylseleno-4-tenbutyl

of the two

& and M towards n-butyllithium. the C-SeMe bond of alkanes thus the corresponding

and that in fact proved to be the case (4a, trans/cis when its stereoisomer

&j is involved

h is expected

to be formed

: 97 / 3, Scheme

moiety

1 entry VII), the

since two effects should work in opposite

The cleavage of the axial C-SePh bond expected on the basis of the above mentioned 5635

a-

of the two selenoalkyllithiums

cyclohexane

protocol is performed on the mixed selenoacetal k bearing the methylseleno

should be different

that the

formed (Scheme 1 entry IQ.

which is expected

available.174 Although

when the above mentioned

possessing

mentioned

& (trans/cis : 96 / 4) without a perdeuteromethylseleno

by a phenylseleno

phenylselenoalkyllitium

on the axial phenylseleno

bearing the perdeuterophenylseleno

mixture

l-phenylseleno-4-ten-butyl

We have in fact recently described

directions.

that axial protonation

3 (Scheme 1 entry VI) under similar conditions.

In order to get further information stereoisomeric

situation

: 96 / 4) with almost

on 1-perdeuteromethylseleno-1-methylseleno-4-tert-butyl

methylseleno

produced almost quantitatively

potentially

above

group remains attached to the cyclohexyl

The same reaction performed

geminally

this result implies

cyclohexyllithium the

cyclohexane analysed

part of the butyl selenide X concomitantly

bearing

b reacts with n-butyllithium

(trans/cis

has taken place, it does not tell which one of the two

takes place almost exclusively

1-seleno-4-tert-butyl

purpose

perdeuterophenylseleno4text-butyl position

4

groups is cleaved by n-butyllithium.

We now report that the reaction

We

cyclohexane cyclohexane

results should

5636

provide the I-litbio-1-methylseleno-4-tert-butyl

cyclohexane

&which

possesses

the less stabilized carbanionic

centre whereas the cleavage of the equatorial C-SeMe bond should provide 1-lithio-1-phenylseleno-4-tert-butyl cyclohexane

a

with the more stabilized

which, from the above discussion, cleavage

of the equatorial

bond occurred

cyclohexyllithium

2

predominantly

rearranged

which the lithium atom is axial, prior to hydrolysis

The mixed corresponding

selenoacetals

required

stereoselective,

the

entering

perdeuterophenylseleno-

seleno

u

have

been

moiety

synthesized

diperdeuterometbyldiselenide

being

table).

In fact, as previously

reported

counterpart.

k

by Duddeck

cyclohexane

chloride

significant

quantities

bromination

of different

determined

been described

regardless

proceeds

work 1-lithio-1-seleno-4-tert-butyl under

with ammonium behaviour.

in

(see

In addition, replacement

of a

the structure

9 (figure). Finally the ones assuming

10 that

with l-lithio-l-phenylseleno-

11, about the stereochemistry that menthyllithium pentane,

with predominant

and often predominant

kinetic

control

cyclohexanes from

seleno-

chloride and diselenides.

We are currently investigating

of conformationally

t&lb, generated

bearing an equatorial

inversion

of configuration.

position.

However,

selenoacetals

deuteration

at Cl in order to supply a reasonable

that in

as has been shown in this arc produced

almost

la. la’. lb. lb’. lc and under from axial attack

It would be surprising if only steric factors are responsible behaviour

and

I-Lithio-4-tert-butyl-

&j and that they react almost exclusively

the stereochemical

or

whereas halogenation

It has been suggested

with the lithium in the axial position or mixed

from menthyl-

and that carbonation,

12b.c similarly.

rigid

C-Li bond is present in

retention of configuration

chloride behaves

control from the mixed selenoacetal

with various substituents

l-

and

different

of -220 ppm 8b. Furthermore

of the halide used for its preparation

available from the corresponding

thermodynamic

origin were remarkably

by X-ray crystallography

these species, the bulky chelated lithium lies in the equatorial

exclusively

Thus

have been

1 entries IV and V). The 77Se

by analogy to the above mentioned

and lithium metal in refluxing

results in significant

cyclohexane

direction. M and k

&.

with dibromcethane

with halogens

axial

cyclohexane

(Scheme

reacts via an axial attack as does dimethyldiselenide

It has however

neomenthyl

the

cyclohexane

*a, an axial PhSe group is about 130 ppm more shielded

Little is known 11, except for cyclopropyllithiums cycloalkyllithiums.

of the

(Scheme 1 entries I and II) whereas &’

respectively

and u

structure of the mixed acetal la’ has been assessed diperdeuterophenyldiselenide 4-tert-butyl

from

The same proves to be valid for MeSe groups.

(m.p.= SO-51°C) has been unambiguously

by selenenylation

l,l-bis(methylseleno)-4-tert-butyl

6b and diphenyldiselenide

&, in

cyclohexane

b by sequential reaction with n-butyllithium

methyl group by a phenyl group results generally in a deshielding of k

been prepared

introduced

cyclohexane

from

5 to its stereoisomer

l-

2. This reaction proved to be almost completely

@Aor dimethyldiselenide

NMR spectra of the two mixed selenoacetals

than its equatorial

have

and 1-methylseleno-1-phenylseleno-4-tert-butyl

prepared from l,l-bis(phenylseleno)-4-tert-butyl

and

: 80 / 20) and that the resulting

& (trans/cis : 96 / 4 ).

cyclohexane

cyclohexanes

THF and with perdeuterodiphenyldiselenide

lithium atom

We in fact found (Scheme 2) that

(&/a

almost instantaneously

for this work

I-lithio-1-seleno-4-tert-butyl

an equatorial

leading finally to I-phenylseleno-4-tert-butyl

: 96 / 4) and 1-methylseleno-4-tert-butyl

& (man&is

centre but which contains

would appear to be the less favourable.

C-SeMe

phenylseleno-4-text-butyl

carbanionic

of l-lithio-4-tert-butyl

solution to this bchaviour.

for such

cyclohexanes

5637

lm 9

X-B = H-NH3Cl 9

X

4.a

H

ii

H H

:

H H

420.0 178.7 199.3 406.0

“Se chemical shifts in ppm at 293%. ku!E

1

X-B =RlSe-SeR1 R1

Yield%

la: ki

C6D5 84% CH3 87%

Ih: id

CD3 c6H5

558.5 311.2 541.4 341.5 406.6 181.9

in CDCl,, Ikk,Se being used as the reference

81% 80%

5638

Referenca 1.

A. Krief, W. Dumont, M. Clarembeau,

G. Bernard and E. Badaoui, Tetrahedron

2.

These analyses

on an Hewlett-Packard

(crosslinked

have been performed

S%methyl

GC/MS

a,

2005 (1989).

5995A fitted with a HP-17

silicon gum phase) column (25 m x 0.2 mm x 0.33 pm ), He as carrier gas,

flow rate : lml /mn. 3.

Some doubt remains quantity

about the butylselenide

of CD3. Work is in progress

surprising 4.

A. Krief, W. Dumont, M. Clarembeau This reaction

has also been followed

reactions

described

bearing

the lithium

corresponding a.

using a more sophisticated

lo-15 % of CH3 besides a large GC/MS

system to understand

this

result.

5.

6

which might contain

Prepared

above. We have observed exclusively

methylseleno by

oxidation

perdeuterobromobenzene b. Prepared

and E. Badaoui, Tetrahedron

a,

2023 (1989).

at -78OC by “Se NMR. It is surprisingly

slower than the related

the 1-lithio-I-phenylseleno-4-tert

in axial position.

(6: 467.4 ppm,

butyl cyclohexane

THF-hexane)

as well as the

analogue (6: 229.3 ppm, TIIF-hexane). 7a

of

perdeuterophenylselenol

itself

(Janssen Chimica) and elemental magnesium

in 40% yield from perdeuteromethyl

synthesised

7b

from

and selenium.

iodide, lithium borohydride-methanol

and elemental

selenium in DMF. 7c 7

a.

A. Krief, A.F. De Mahieu, W. Dumont and M. Trabelsi, Synthesis,

b. D.C. Foster, Organic Reaction,

8

c.

M.Trabelsi,

a.

H. Duddeck,

unpublished

results from our laboratory.

P. Wagner and S. Gegner, Tetrahedron

b. N.P. Lutbra and J.D. Cklom in : “The Chemistry Patai and Z. Rappoport 9

a.

crvstal

da

I&t. 26, 1205, (1985)

of Organic Selenium and Tellurium

: C17H26Se2, MR = 388, monoclinic,

using an Enraf-Nonius

2053 unique observed direct method

and refined

Data Centre,

a = 18.970(11),

and Mo-Ka

radiation

b = 8.728

(x = 0.7 1069 A), with

[with I > 1.9 o(I)] having 2 8 < 52’. The structure by full-matrix

9b. The atomic coordinates

Crystallographic

space group P21/c,

S.

II

V = 1786 A3, Z = 4, Dx = 1.443 g.cm-3, X-ray data were

CAD-4 diffractometer,

reflections

SHBLX-86

(SHBLX-76)

Compounds”,

Ed., J. Wiley & Sons Ltd. (1986), vol. I, ch. 6, pp. 189-241

(15), c = 11.280(6) A, p = 107.027(24)‘, collected

131, (1988).

Coll. Vol. 3,771 (1955).

University

was solved by

least squares to a current residual

R of 0.04

for this work are available on request from the Cambridge Chemical

Laboratory,

Lensfield

Road, Cambridge

CBE

IEW, Great Britain. b.

G.M. Sheldrick,

SHBLX-76,

“Program for crystal structure determination”,

University

of Cambridge,

England (1976). The neutron diffraction

10.

of u

11 a, D.J. Cram in “Fundamentals A.T. Blomquist b.

B.J. Wakefield

will be performed of Carbanion

soon.

Chemistry

: Organic Chemistry,

a series of monographs”,

Ed., New York (1965). in “The Chemistry

of organolithium

Compounds”,

Pergamon

Press, Oxford, England

(1974). 12 a.

W.H. Glaze and CM. Selman, J. Org. Chem. 3,

1987 (1968).

b. W.H. Glaze, C.M. Selman, A.L. Ball and L.E. Bray, J. Org. Chem. 2,641 c.

W.H. Glaze and CM. Selman, J. Grganometal. (Received

in

UK 25 August

1989)

Chem.,11, P3 (1968).

(1969).