Synthesis of di-, tetra- and penta-methyl-heptalenes

Tetrahedron printed in

Letters,Vol.27,No.l5,pp Great Britain

SYNTHESIS Klaus Institut

Hafner*,

Norbert

fiir Organische

Summary:

tives with electron

these substituents

crystals

unstable

L.

Knaup,

Hochschule,

and

Klaus-Peter

Petersenstrasse

by two different

to be, in contrast

and air sensitive

substituents

Meinhardt

22, D-6100

pathways.

to the parent

Darmstadt

The new compound,

of the recently

depending

prepared

on their number

12r-electron

system, were known

1,2,5,6,8,10-hexamethylheptalene5

heptalenes

to prepare

heptalene 192 only derival,;d,3,4 or 3-(58) positions , which

unsubstituted

in l-(:5,6,10)

of the bicyclic

lower methylated

so far. The

stimulated

in order to prove the stabilizing

ef-

effect of

and position.

these heptalenes

in a similar way as the hexamethyl

1,2_heptalenedicarboxylates

azulenes -lb-d with dimethyl hydride

PENTA-METHYL-HEPTALENES

were synthesized

stabilization

As it seemed promising tive5, the dimethyl

Giinter

7a-d and -10 proved --

withdrawing

stability

forts to synthesize

AND

and air stable.

from the thermally

cause an electronical

TETRA-

Hock,

Some methylheptalenes

thermally

unexpected

DI-,

Chemie der Technischen

hydrocarbons

Apart

OF

0040-4039/86 $3.00 + .OO 81986 Pergamon Press Ltd.

1669-1672,1986

2b-d - obtained by cycloaddition reaction -4 acetylenedicarboxylate - were reduced with diisobutylaluminum

to the 1,2-bis(hydroxymethyl)-heptalenes

3b-d, which

could be isolated

derivaof the

as stable yellow

(Tab. 1).

R2

R'

MeC$C-CnC-C$Me /'\

R3 207“C

*

c&3

T::;c--#R3

Q RL HO

1

2 l-3,6,7 ---_

Attempts

to synthesize

3

a

b

c

d

Me Me Me Me

H Me Me Me

Me Me H Me

H H H Me

1,3,5,6,7_pentamethylheptalene

i - generated

via the 1,2-bis(chloromethyl)-heptalene

from the diol -3b with phosphorus pentachloride - failed as -l, eliminates spontaneously HCl to give the 1,2_bis(methylidene)-heptalene 5. - This result prompted us to study the

1669

1670

3b

pc’5 CHC$

I-60

OC r

‘c,rJy

:-c,&

Cl

dehydration

of 1,2-bis(hydroxymethyl)-heptalenes

2, which

(similar to 2, OH instead of Cl) to the 2-heptalene As expected, amounts

the heptalene

carbaldehydes

diols 2 can easily be converted acid (Tab. 1).

of p-toluenesulfonic

R’

Decarbonylation

':&R3

5 with tris(triR2

(Ph3Pl3RhCI CgHfj

phenylphosphine)rhodium(I)choride stable compounds

of the aldehydes

with catalytic

R’

CfjHfj I 8OOC

unsymmetrically

structure

-6.

into 5 by reaction

R*

TsOH 2-4

should lead via an enolic

yields

(Tab. 1 and 2). Similar substituted

e

hydrocarbon

I 8OOC

the desired methylheptalenes

1 as thermally

to the heptalene

2, 3, and 5, even the

derivatives

7b exists at 25'C as a mixture

Y&R3

and air

of the bond shift isome!rs

m

X

In addition rent pathway

to -7a-d we also could synthesize

1,6_dimethylheptalene

after the cis-l,Sa,6,lOa-tetrahydroheptalene

derivative

-10 by an entirely -8 became

diffe-

easily accessible

1671

by a new rearrangement reaction.6 -10 is obtained by reduction of the diester 5 with diisobutylaluminum hydride and subsequent two-fold dehydration of 2 (Tab. 1 and 2). The surprising stability of the described methylheptalenes- even of the dimethylheptalenes 192 can not only be the result of a kinetic -7d and -10 - in comparison with the parent compound stabilization due to a steric shielding of the heptalene system, but rather to an enhancement of twisting of the nonplanar12n-perimetercaused mainly by a steric interaction of an increasing number of methyl groups in the peri-positions.This reduces the cyclic conjugation and increases the HOMO-LUMO gap of the [4n]-x-system.

Tab. 1: Yields and Physical Data of the Compounds 2, 2. 2, 2, 1, 2, and 10.7 Compound

Yield[%l

mp[“Cl

ratio A:B 4:l

Uv)Imax(lgE)Inml 268(4.19), 323shc3.571, 393sh(2.791b)

-2bd) 2c

56

99-100

32

113-114

>’ -

35

-3b -3c

86

124-129

1:2

246sh(4.22),

86

130-131

9:l

253(4.32),

300sh(3.491b)

-3d

33

128-130

7:s

255(4.34),

317(3.53jb)

-5

18

133-136

223(4.37),

286(3.82), 247sh(4.19),

113

>98:<2

262(4.19),

273sh(4.17),

205(4.40),

264(4.21), 258(4.33),

326sh(3.381b) 323sh(3.52),

405sh(2.66ja)

316(3.581b)

389(4.011b)

-6a

94

132-134

1:2

218(4.26), 372sh(2.92)b)

-6b

67

112-114

1:20

253(4.25),

271(4.29),

328(3.63),

396sh(2.851b)

1:6

253(4.27),

271(4.30),

330(3.65),

394sh(2.841b)

248(4.11),

254(4.11)=)

6c

56

90-91

Zf) -

28

oil

-7a

86

78-83

-7b

63

59-61

-7c

46

73-74

-7d

44

-9

76

-10

32

oil

252(4.36),

299sh(3.49)a)

252(4.36),

317sh(3.57)a)

251(4.34),

295sh(3.47ja)

oil

250(4.33),

333(3.59ja)

140-142

236(4.11),

243(4.12),

251(4.34),

332(3.59)a)

1:3

256sh(4.23),

271(4.28),

a) in hexane b) in dioxane c) in methanol d) in contrast to an earlier publication4a the reaction affords no dimethyl 5,6,8-trimethyl-2,3_heptalenedicarboxylate e) additionally 13% dimethyl 6-methyl-1,2-heptalenedicarboxylate (orange plates, m.p.: 139-14O’C)

can be isolated

f) could not be obtained as pure compound so far

Tab. 2: -7a:

6=

300 MHz-~H~NMR spectra of the methylheptalenes1 and -10 (in CDC13);TMS as int.stand.): 1.72,

1.74(2s;

3H each, l/6-Me), 1.97(d, J= 1.4Hz; 3H, lo-Me), 1.98(d, J= 1.6Hz; 3H,

S-Me), 1.98(d, J= 0.6Hz; 3H, g-Me), 6.00, 6.10c2br.s; 1H each, 7/9-H), 6.10(m; lH, Z-H), 6.28(m; 2H, 3/4-H). 7bA: 6= 1.71, 1.74(2s; 3H each, l/6-Me), l.gS(covered;3H, S-Me), 1.98(d, J=1.3Hz; 3H, 3-Me),

1672

5.78(d,

J= 10.4Hz;

7-H), 6.20-6.40(m;

IH, 10-H), 5.93(br.s;

1.95(d, J= 1.3Hz; 3H, l-Me), 2.0l(br.s;

7bB: 6= 1.71(s; 3H, 5-Me), 3H, 3-Me),

5.71(d,

7c:

lo,

J= 6.OHz;

IO-H),

IH, 7-H), 6.27(ddd,

6.14(d, J= 5.8Hz; 6.OHs;

IH, Z-H), 6.07(br.s;

lH, 4-H), 6.lO(covered;

IH,

2H, 8/9-H).

5.9o(q,

J= 1.2Hz;

3H, 6-Me);

2.05(d,

IH, 2-H), G.ll(br.s;

J= 11.1, 6.0, 0.6Hz;

lH, 8-H), 6.38(dd,

J= 1.2Hs;

lH, 4-H), J= 11.1,

IH, 9-H).

6= 1.74(~; 6H, 5/10-Me),

1.99(d, J= 1.4H.z; 6~, l/6-Me),

6.13(m;

2H, 2/7-H),

6.3O(m;

4H,

3/4/8/9-H). 7d:

6= 1.73(s; 3H, l-Me), 1.99(d, J= 0.9Hz;

IH, 5-H), 5.86(d, J= 10.9Hz;

(d, J= 6.OHz; 10:

,+ 2.1O(d, 2/7-H),

3H, IO-Me), 5.44(br.d,

J= 0.5~2;

6.12(dd,

6H, l/6-Me),

J= 11.1,

6.3Hz;

J= 5.9Hs;

IH, 6-H), 5.94-6.40(m;

5.64(d,

J= 6.3Hz;

2H, 3/8-H),

5H, 3/4/7/8/9-H).

2H, 5/10-H),

6.32(dd,

J= 11.1,

lH, 2-H), 5.66

5.99(br.d,

6.3Hz;

2H,

J= 6.3Hs; 2H,

4/9-H).

ACKNOWLEDGEMENT Support

of this work by the Deutsche

REFERENCES

AND

L.A. Paquette,

2.

a) H.J. Dauben,

Engl. __-

D.J. Bertelli,

J. Wassen,

J. Am. Chem. Sot. -83 (1961)

K. Miillen, J.F.M. Oth, Angew.

J. Am. Chem. Sot. 102 (1980) 643;

hoff, J. Wassen, E. Vogel,

Angew.

A.R. Browne,

D. Kerimis,

Chem. Int. Ed. (1979) 581;

E. Chamot,

N.T. Allison,

J.F.M. R. Zeller-

(1979) 545.

Chem. Int. Ed. Engl. 13

Chem. -86 (1974) 779; Angew.

H. K8nigs-

Chem. 91

Chem. Int. Ed. Engl. 18

Chem. -86 (1974) 778; Angew.

Angew.

b) E. Vogel,

E. Chamot, Angew.

d) E. Vogel,

Chem. -91 (1979) 579; Angew.

J. Ippen, Angew.

E. Vogel, F. Hogrefe,

4659;

Chem. -86 (1974) 777; Angew.

A.R. Browne,

Chem. Int. Ed. Engl. -18 (1979) 546; L.A. Paquette,

Blount,

Industrie,

acknowledged.

Isr. J. Chem. -20 (1980) 233.

13 (1974) 732; c) L.A. Paquette,

Angew.

3.

is gratefully

NOTES

1.

hofen,

the Fonds der Chemischen

Forschungsgemeinschaft,

and the Dr. Otto RGhm Gedachtnisstiftung

(1974) 734;

Chem. Int. Ed. Engl. 12

(1974)

735. 4.

a) K. Hafner,

H. Diehl,

H.U. S&s,

-15 (1976) 104; b) K. Hafner, 209; Angew.

Chem. -88 (1976) 121; Angew. H.J. Lindner,

K. Hafner

6.

K.-P. Meinhardt andK.

7.

All new compounds

and G.L. Knaup,

Tetrahedron

Hafner,

Lett. -27 (1986),preceding

unpublished

Chem.

Angew.

Int. Ed. Engl. Chem. 97

(1985)

have been characterized

(G.L. Knaup, Dissertation

in

Germany

4 February

paper.

results. by IR, 'H NMR (300 MHz), MS, and elemental

TH Darmstadt

1986). (Received

H.-C.FlGter,

Chem. Int. Ed. Engl. 24 (1985) 212.

5.

analysis

Angew.

G.L. Knaup,

1986)

1985; N. Hock, Diplomarbeit

TH Darmstadt