Synthesis and tautomerism of persubstituted 1,3-dianils, and substituent rotation in their chiral nickel complexes

Tetrahedron Letters No. 5, pP 459-462, 1977.

SYNTHESIS AND

AND

TAUTOMERISM

SUBSTITUENT Rudolf

Institut

IN THEIR

Alfons

fiir Organische Karlstr.

Rinted in Great Britain.

OF PERSUBSTITUTED

ROTATION

Enorr,*

Pergsmn Press.

CHIRAL

WeiD,

Chemie

23, D-8000

1,3-DIANILS,

NICICEL COMPLEXES

and Heinz

Polzer

der UniversitPt

Miinchen

Miinchen 2, Germany

(Received 30 November 1976; received for publication 6 Jaaaary 1977) Whereas

malondianils

dialdehydes

be synthesized tion"3

from

takes

ents.

Therefore,

tion,

based

the primary is added

product

after

hydrolysis or may avoid

ca.

with

its

trans

The

liquid,

and

75$ s

coupling

as well

groin

employed

in CC14)

from

E

We performed lysis;

Yields

a structural

lation

normally

was

authentic not

substitu-

for

whereas

ppm,

?&

@

I-propanol were

follow

ppm,

After

70°C

symmetry in CC14.

to

of 2546 Lg 2

Because

atb = 7.70 (NH 3.72

(CH 3.57

Crystallization

equilibrium

of the

characterized

and NH resonance

(NH 12.5 ppm).

CH3Li

or distilled below

the

6 = 14 ppm'

60s

acid

Since

26-96s.

from

consists

The

is evolved.

is crystallized

contains

(NH 5.40

hours.

of 2, more

methane

or

stochio-

of the imidic

(E)-configuration

= 12 Hz9

with

two hours.)

for 40-80

regeneration

ara;out the

s/z

for

no more

of 0.2

of methyllithium

be refluxed

one equivalent

6a-e

by addition

instantaneously,

atmosphere

(in ethanol

J(R2,R3)

by ppm.

ppm)

ppm,

t with

from

concentration

li85%

1546).

proof

7146 of dipivaloyl-methane with

cyclization4

two bulky

the amount

(not optimized)

Kf assumes

to separate (CH 5.03

and

the dianil

pure lo mixture,g/a

ppm),

begin

2f must

until

work-up,

as the horseshoe

identified

added

with

the NH absorption

constant

of C/N-condensa-

out in ether

not

by 2 with

(Z)-structures

analytically (CH2 3.35

was

in ether

as the perchlorate

and/or

malon-

(Ri + H) cannot

quinoline only

lithio-N,N-diis&opyl-amide

ca. 30 hours

R' substituent,

J P 7 Hz)

are

or Cl) in an inert

formation4).

spectrum

of its bulky

does

7 is deprotonated

The horseshoe-shaped 'H nmr

2 is carried

of methane

ice and basic

be purified quinoline

methods

for 5g with

(Pinacolone-anil

15 and

5

synthetic method with C/C-condensa6 5 by Marekov, Stork, and Wittig. 7

heated

(X = OC2H5

2

substituted

a different

of pre-formed

salt 2 is then

derivative

from

1,3-dianils

the Beyer-Combea

even

of N,N-diisopropyl-amine

amounts

lithium

5,

is true

work

increased.

accessible

acyclic

1. If conventional

of azomethines

If evolution

correspondingly metric

This

we designed

on previous

equivalents

easily

to nmono-anilsn

place.

deprotonation

methyllithium.

are

persubstituted

1,3-diketones

are applied

invariably

The

like &

?_ (R1=R3=H),

of C/C-condensation lg were

specimens.

The

observed. 459

isolated alternate

for

7/8g by acid

as the cip&r possibility

complex

hydroand

of N-iminoalky-

No. 5

P’

R2 R3

R'

0

II \Hp

Ph

Ld

/N

0 R’\c/CH

+CH3Li

>

II

-CH/+

cs

1 R2

2

H R2

//

R3

/,

R3

R’

> PhHN

a

H

b

/\ 8 / CH3 23

126-128

Ii

1-1

CH3

8\/

CH3

CH3

SCgH5

CH3

(CH2)G

112-113

H

H

=4H9

H

tc4H9

86s

with

C2H5

nC3H7

cH3

‘6”5

=4H9

CH

c6H5

*C4H9

fully

yields

from

the

in THP

with

hexane

aipitation

with

ethanol

Projecting

ligands 2

(e)

B configuration.

3

102-103.5

1,3-dianils

[(C2H5)4N]2NiBr4

symmetrical

[140/10’3

11

paramagnetic

extraotion

with

98-99.5

nC3H7

Tetrahedral,

H‘N\Ph

CH3

tc4B9

3

N\Ph

($)

\

CH3

R3

Li@

PhAN

?

X\C/

(jg

93-95



nickel

complexes

by treatment

for

or benzene,

.

12-86

hours

with under

,9 crystallize8

*

2 10

2 were

methyllithium 12 After N2. from

dry

prepared

in 0 -

and heating evaporation and

ethyl

acetate

(pre-

We select here cases 9a, Et and 2 with if necessary). 13914 ) for a study of substituent rotation. chirality along the axis C3Ni.C3' from the right, one obtains Jl_

(axial 14

The

cyclohexenyl

double

bonds

are

symbolised

by two

No. 5

461

9a 12, s

11, R

one above

wedges

4,

(rear)

chelate

hydrogen) one for

we 4

expect due

lohexenyl will

Since

nickel

may

of the anilino

(C12CD)29

in reasonable

with

Due AG+

having

0

(2)

one

to the left

of the vertical

q

axis

(C,). Rotations

z

ligand

with

more

interchanged

than

be obtained

in E.

agreement

similar

with

the a/b We find barriers

methyl/hydrogen

repulsions, in

23 kcal/mol, from

moieties

nmr

by

as a whole

coalescence AG* for

repulsions

the relevant

nickel

cyc-

inver-

chemical shifts a and b. 13 the smaller barrier of

non-equivalences

(C12CD)2;

180~ of the rear (i.e.,

of the p-hydro-

= 16 kcal/mol

(320 K)

2,2'-dimethyl-biphenyl in a planar

transition

in IJ disappear J values"

(ppm)

at 240K are

shown

= 2-H and 4-H. 16 l-phenyl-naphthalene whose rotatiofor the non-planar 17 Enantiomeriaation requires AG* = 15.2 kcal/mol at ia unknown.

is a model

nal barrier K in

to weaker

= 9.8 kcal/mol

12 for

351

needs

signals

state.

e

symmetry

enantiomer

rotation

and

chemically equivalent groups (CHg or aromatic p1 Ii nmr absorptions (a,b) of equal intensity, but only

or of the rear

inversion

derivatives15

in

two

to the

produce

cyclohexenyl

in

the horizontal For

substituent

sion)

gen

ring.

(C12CD),.

to nitrogen

is n:t

-389

Hindered

rotation

observed

for 2

of the phenyl (e)

-379

groups

but detectable

_

about

for jJ

their

(12;

bonds

AG'

=

462

No.

12.1 kcal/mol mol

at 238 K), 2

(17.7 kcal/mol

(12;

(340 K) found

2

12.8 kcal/

at 253 K).

The highest (C12CD)2 group

barrier

deserves

about

the bond

transition

state

process.

We gratefully

Deutsohe

AG8

special

the latter

and

= 17.4 kcal/mol attentiun.

It could

to C3 or to Inversion therefore

acknowledge

constitutes

support

be due

for

(9d) in

to rotation

of the SC H 65 a linear

of divalent sulfur via 18 another lower energy

by the Stiftung

limit

Volkswagenwerk

for

and

the

Forschungsgemeinschaft.

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AND

NOTES

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A.