Synthesis of indolizines from pyridinium(trifluoroacetyl)methylide and fluorinated dipolarophiles

Journal of Fluorine Chemistry, 34 (1986)

215-219

Received:

22, 1986

July 28, 1986; accepted

PRELIMINARY

August

NOTE

of

Synthesla

ERIC

and

and

BANKS*

SUAD

Department,

Chemistry Institute

of

Manchester

and

Pyridinium

Fluorinated

NAJMALDIN

Dipolarophlles

MOHIALDIN

of

Manchester

been

synthesised

University

The

Science

M60

from

Indolizines

(Trlfluoroacetyl)methylide

RONALD

275

Technology.

(U.K.)

1QD

SUMMARY Some via

new

fluoroindolizines

1.3-cycloaddition

(mainly) (VII)]

[CF3cfN

+ and

Treatment

(IV) dimethyl

of

(III)

between

reactions

(trifluoroacetyl)methyllde dipolarophiles

have

and

(V):

(1)

and

(II);

CF3C3CF3

base

fluorinated __)

CF3C=_CH-(VI):

acetylenedicarboxylate with

pyridinium

converted

CF3CFZCF2+ [---,

it

(III)

to

(VIII)].

(IX)

-CHCOCFj C F&O

-3

(II1

(II * To

whom

enquiries

0022-l

139/86/$3.50

should

be

addreased. 0 Elsevier Sequoia/Printed

in The Netherlands

276

I’ N AZ %X

Y

(III)

X = COCFj

(IV)

X

(V)

X = COCHFZ,

(VI)

X = COCF

(VII)

X

(VIII)X

has

to

route

tedious, (I)

development

enabled

pioneering

studies

indolizlnes

via

methylidic

Y

= F.

= COCF3

, Y

= Z = COZMe

. Y

= Z = CF3

Cl]

the

[2.3]

on

the

to

time

synthesis

of

cycloaddition

though

extend

our

fluorinated

reactions

substituent

to at

a

the

pO.3itiOn.

(I.)

and

trifluoroacetonitrile, 3.3.3-trifluoropropyne,

and

hexafluoropropene to

yield

indolizines isolated

6P-66'C): 12n-126°c).

DMAD

complex

proceeded

products

(l-azaindolizine chromatographically

119-121

Oc):

VII

isolable

the

between

hexafluorobut-2-yne,

m.p.

Z = CF3

a simple.

Of

first

fluorinated

trifluoroacetylmethylide

DMF

3

(trifluoroacetyl)methylide

for

Reactions

in

= 2 = CF3

, Y = H. Z= CF

3

recently

a

2 = l-l

3’

, Y

1.3-dipolar

carrying

dipole

CF

= COCF3

pyridinium

us

= 2 = CF3

,Y=

3

X=H

(IX)

The

= COCF

, Y

(10%.

III

(20%.

m.p.83-85

respectively].

from

room

which

the

case

low

yields

in in

at

m.p. 'C):

the of

50-52'C): and

temperature

VIII

CF

expected

3

CN)

I

II

VI

(a%.

(70%.

were (10%. m.p. m-p.

277

PY

PC HO

CF,

-3

(XI)

(Xl

Itl

the

case

of

trifluoroacetonltrile. pyridlnium m.p. the

a

methylide

183-185°c): production

was

of

the

by-products

(IV:

involving

hexafluorobut-2-yne.

1.5-dipolar

cyclization

the

source

possible deferred

of

the

routes

to

to

a

full

postulated

(XII)

and

(see

the

be

in

The the

Scheme)

difluoroacetyl Neither involved

of

its

involved

in

isolated.

analogues th@

(e.g.

XIII)

1,3-cycloadditions

yield, view

of

pyrldlnium

the

formation

the

cycloaddition

the in

of

incursion

of

is

to

thought discussion

compound

a

be of

(V)

Is

dihydroindollzine the

3-trifluoroacetyl-2-trifluoromethylindolisine any

the

[3].

was 3%)

in

from

indolizine;

former

paper. to

(V:

be

(6%

unexpected

CF3CN

however,

to

isolated

(XI)

and

anticipated. 4%)

not

analogue

(t-butoxycarbonyl)methylide

Not

also

was

again

involving

believed

product

(X)

this

reaction

the

formation (IV).

presumably reported

[cf. here

of nor 2,111 were

270

tIl

CF,CXCF,

(-2H)

Treatment reaction

of

of

hydroxide

gave

44-&6'C)

All possessed

in

the correct

spectroscopic consistent

the

pyridinium

hexafluorobut-2-yne

m.p.

(IV1

kCHF,l

Scheme

from

(III)

the

(trifluoroacetyl)tnethyli.de

with

hot

alcoholic

with sodium

aqueous

1,2-bie(trifluoromethyl)indolizine 58%

yield

new

(after

the

[IR.

structures

NMR

('H,

assigned.

here

claimed

compositions

elemental

OX;

recrystallization).

(II-X)

compounds

properties with

product

major

(C.

19,.

13C)

H. and

N)

and

mass]

279 1

2

3

H.

Wittmann.

H.

G.

van

R.

E.

33:

LIbid

R.

E.

(1983) the 11 R.

E.

Ziegler,

Schnering,

Banks

and CM),

Banks 589:

J.

K.

Peters,

Monatsh. Thomson,

E.

Chem.. J.

Chem.

M.

j.&

Peters.

(1983)

Res.

(S).

and

1097. (1985)

0671-0689.

and +.

J.

Thomson,

J.

Chem.

M.

Hitchen.

J.

Sot.,

Fluorine

Perkin

Chem.,

Trans.

I,

-22 In

press. E.

(1982)

Banks 373.

and

S.

J.

Fluorine

Chem.,

0