Reaction of spironaphthalenones with hydroxylamine: Part III. A novel mechanism for the formation of products and trapping of an intermediate.

00404020!93$mO+.OO 0 1993Pergamim PressLtd

Te?rah&onVol. 49.No. 1,pp. 135-140.1993 Printedm GreatBrnain

Reaction of Spironaphthalenones with Hydroxylamine: Part III. A Novel Mechanism for the Formation of Products and Trapping of an Intermediate.

Tirumalai R.Kasturi*,Kaipenchery A.Kumar,Palle and Gundi Sridevi

V.P.Pragnacharyulu

Department of Organic Chemistry Indian Institute of Science Bangalore - 560 012,India. (Received in UK 27 August 1992)

mechanism involving of nitrene 5, formed the intermediacy from the oxime of spironaphthalenone 1 by acid catalysed dehydration, has been proposed to explain the formation of pyrrolotropones / pyrrolo esters to the from spironaphthalenones. The initially formed nitrene rearranges isopyrrole 6, which either undergoes sigmatropic migration to the pyrrolotropone 2 or adds alcohol to form the pyrrolo ester depending on substitution at 1' position.The isopyrrole intermediate 6 has been trapped as a Diels-Alder adduct 8.

Abstract : A

We proposed

have by

recently1

provided

evidences

Dean et.a12 for the conversion

pyrrolotropone

2 6’

is

to show of

not correct. Further, we

that

the

mechanism

spironaphthalenone have

also

reported3

5’


6” 1 ;

-

=3

a)

R=H

b)

R = 4-0CH3

C) R=4-NO2Ph

Ph

a) R = 4 -OCH3Ph ;’ R’=E1 b)R=4-N02Ph ; R’=E1

I2 Scheme

135

1

R H

0

C02R’

%:

la

’

/

N-oH

4 a) R =T-0CH3Ph b) R q4 -NOZPh

to the

137

Reactionofspironaphthalenoneswith hydmxylamincAII

The

formation

spironaphthlenones

of

1

from

3

l'-

substituted

aryl

7. As aromatisation

of 3 (Scheme 2). Alternatively,

pathway to addition

of 7 is not feasible, result

in

the

this ester 3 could arise by

the

to 7 followed by a facile bond cleavage would

alcohol

formation

esters

can also be presumed to follow a similar

give the dihydrotropone of

pyrrolo

addition of alcohol to 6 itself. Nitrene$ have been postulated rearrangement

of

oximes

in the acid catalysed

as intermediates5

(Beckmann rearrangement

and

addition

1, and the

insertion of nitrenes to suitably oriented groups have also been documented in

literature6.

isopyrrole

In

like

the

conversion

intermediates

have

of

to

azide

biphenyl

carbazole7,

Intramolecular

postulated.

been

are of nitrenes derived from azides to give Spiro intermediates insertion 9-11 8-10 reported . Also sigmatropic migration of C-S group8 or acyl groups such Spiro intermediates

in

have been invoked to explain the formation

products.

The

present postulation

of a nitrene intermediate

insertion

followed by acyl migration

to give 7 (Scheme 2) has

of its

and

6

undoubtedly

many analogies. It

was not possible to isolate any intermediate

spironaphthalenone

after a very short interval.

reaction could

with hydroxylamine

not

be

intermediate

6

hydrochloride

in the

It is strange that

isolated. Attempts were then made to by using suitable dienophiles.

reaction

even

trap

the

the

the

hydrochloride

lb

oxime

No adducts could be isolated

or dimethyl acetylenedicarboxylate.

reaction of spironaphthalenone

the

isopyrrole diethyl

when the reaction was carried out in presence of maleic anhydride, maleate, N-phenymaleimide

of

even after stopping

was carried out with

in ethanol in presence of acrylonitrile,

we

However, when hydroxylamine obtained

after

work up, a white solid (M+ 419, analysing for C 8H21N03 ) in 20% yield 3 addition to a small amount of pyrrolo ester 3a . This compound showed

in

carbonyl

lH

absorptions

in its IR spectrum. The compound exhibited

in its

NMR a methoxy signal at 6 3.62 and a singlet at 6 5.38 integrating

for

no one

proton. Based on the spectral data, this compound was shown to be the oxime rla(Scheme 1). This was

the first time that an oxime was isolated

reactions12. When the oxime 4a a

in

these

THF was refluxed with ethanol containing 3 trace of acid, we obtained after work up the corresponding ethyl ester

3a

in

prepared 3b that

nearly quantitative

in

yield. This experiment was repeated

from spironaphthalenone

was obtained in about 80 % yield.These the formation of the

using

Ic. In this case also, the pyrrolo experiments

oxime is the first step in

reaction and further confirmed our earlier observation

undoubtedly this

1

NH20H.HC1 is enough to take the reaction to completion.

4b

ester proved

rearrangement

that one mole of

T.R.KASTURI et al.

The

thus prepared, could serve as

oximes,

carrying

out

experiment5

trapping experiments with acrylonitrile

with

Initial

dienophiles.

and diethyl maleate were

unsuccessful

when the oxime 4a was refluxed with excess of 2-chloroacrylonitrile containing

a trace of acid, we obtained after careful

preparative

TLC,

absorption5

at 2;80 ( CRN 1 and 1680cm-'(unsaturated

exhibited in its a

singlet

a

yellow

compound

in

H NMR signals at 63.6

at dl.1

integrating

very

in

yield

and

showing

IR

C=O 1. This

compound

to methoxy

group and

for two protons. Based on

data , the compound was tentatively

but THF

chromatography

small

corresponding

for

substrates

suitable

different

assigned the structure

these

spectral

8. The structure

of this compound was further confirmed by its mass spectrum which showed an ion at m/e 401 (relative intensity Alder fragmentation

116.99 ( C3N 1

and 6198.76

also

( CH2),

(unsaturated C=O 1. Isolation of the adduct intermediacy

rearrangement. Thus, the common intermediate or

Diels-

was

by its 13C NMR which showed signals at656.10

proved the postulated

pyrrolotropones

to the retro

of compound 8. The structure of this compound

further substantiated

unambiguously

60% 1 corresponding

of

isopyrrole

6

in

7 can explain the formation

pyrrolo esters depending on the

substitution

at

8

the of l'-

position of spironaphthalenones. rearrangement

Utility of this n6vel

compounds of possible biological

of a variety of

interest is being studied at present.

EXPERIMENTAL

SECTION

All m.ps reported are uncorrected. a

in the synthesis

Hitachi model 270-50 double wavelength

-1 IR (cm 1 spectra were recorded on /double beam

spectrometer.

spectra were recorded on a Jeol FX-9OQ(90 MHz) or a Bruker-400(100.62 13 Mass spectra C ) instrument using TMS as an internal standard. recorded

on

a Jeol MS-DX 303 spectrometer

with a builtin-inlet Oxime

and

at 70 ev

MHz, were fitted

system.

of l'- (4-methoxyphenyl)-spiro(naphthalene-l(2~),2'(1'~)-naphtho[2,l-b]

furan)-2-one

was

operating

NMR

added

containing mixture

(4a

to

): A solution of NH20H.HC1

(0.53 gm ) in ethanol

(5

ml)

(1 ml). Five drops of conc.HCl was added and

the

a solution of spironaphthalenone

acrylonitrile

THF

(10 ml)

lb (1 gm) in

refluxed with stirring for 48 hrs. The reaction mixture

was

then

concentrated

and the resulting solid filtered and recrystallised from CHC13 to give 4a in 20% yield; m.p. 212OC; IR (nujol) 1630 cm -1; 1H NMR (90 MHz,

CDC13 1

3.62 (s,3H,0CH3 1, 5.38 (s,lH,benzylic CH), 6.4-7.9

MS: m/e 419 ( M+, 251,402

( m,l7H, ArH);

(90) and 283 (100%); Anal. Calcd. for

C, 80.19; H, 5.01; N, 3.34. Found. C, 80.43; H, 4.46; N, 3.43%.

C28H21N03:

139

Reaction of spironaphthalenones with hydroxylamine_nI

The

filtrate, after purification, gave ester 3a(50 mg) identified

by

spectral data3. Oxime of l'- (4-nitrophenyl)-spiro(naphthalene-1

(2~),2'(1'FJ)-naphtho[2,l-b1

furan )-2-one (4b): Reaction of spironaphthalenone lc (1 gm) with NH20H.HCl (0.52 gm) in THF/ethanol containing acrylonitrile (1 ml) and 5 drops of cont. HC~, followed by workup as mentioned above resulted in 4b in about ) 5.43 28%yield: m.p. 228OC; IR (nujol) 1632 cm -1; 1H NMR (90 MHz, CDC13 6.9-8.0 (m, 16H, (srlH, benzylic CH ), 6.78 (d,J=lO Hz, lH,d-styrene), ArH); MS: m/e (424 M+, 20 ), 417 (60),. 282 (100%); Anal. Calcd for C, 74.65; H,4.14 ; N, 6.45. Found: C, 75.07; H,4.45 ; N, 6.68%. C27H18N204: The filtrate, after purification, gave ester 3b(35 mg) identified by spectral data3. of Oxime 4a /4b with ethanol: A solution of oxime 4a (100 mg)

in

THF (3 ml) was refluxed with ethanol containing a drop of cont. HCl for

24

Reaction

hrs. Solvent removal followed by column chromatography

( silica gel, CHC13)

reaction resulted in the ethyl ester 3a3 in quantitative yield. Similarly oxime 4b with ethanol resulted in the corresponding ester 3b3 in 80 %

of

yield. l'-(4-Methoxyphenyl)-1',3'-(1"-chloro-1"

-cyanoethano)-spiro(naphthalene-

1(2l!J),2'(1'FJ)-naphtho[2,l-b]pyrrol)-l-one(8) : A mixture of oxime 4a (900 mg) in THF (20 ml) containing 2-chloroacrylonitrile (13 ml) and 6 drops of HCl was refluxed for 48 hrs with stirring. Solvent removal

cont. by

purification

of

the residue by column chromatography

(

silica

CHC13:hexane ) and preparative TLC ( silica gel, CHC13:hexanF compound

8 in

1% yield;

m.p.

210°C (d): IR (nujol) 1680 cm

followed gel,

)lresulted in ;

HNMR(

90

13 CDC~~ ); 1.22 (~,~H,cH~), 3.78 MHz, (s,3H,0CH3), 6.66-7.90 (m, 16H,ArH); c NMR (100.62 MHz, CDC13 ); 55.15, 56.10, 64.08, 96.1, 111.98, 113.11, 113.68, 116.99, 122.98, 123.08, 123.22, 124.97, 126.97, 126.82, 127.64,

128.20,

128.42, 128.67, 128.82, 128.99, 129.99,

130.10,

130.37,

130.79, 130.94, 131.21, 139.06, 145.82, 158.96, 158.65, 198.70; MS: m/e 401 (50 ) 373 (15), 83 (lOO%);Anal. Calcd. for C31H21C1N202: C, 76.29; H, 4.30; N, 5.76. Found C, 76.10; H, 4.23; N, 6.16%. ACKNOWLEDGMENTS

the

We thank Dr. A.Sarkar, NCL, Pune and Dr. K.A.Reddy, REC, Warangal

for

analyses reported herein.Thanks are due to SIF, Bangalore for the

NMR

Panjim

and

spectra.

We also thank Prof. S.K.Paknikar, University of Goa,

140

T.R.K~STmret al.

Prof. G.S.R. Subba Rao and Dr. A. Srikrishna of our Department discussions. Financial assistance Research

and

from Council of Scientific

National Science Academy, New

Indian

Delhi

for

helpful

and Industrial is

gratefully

acknowledged. REFERENCES 1.

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