Cation radicals in the bromination of benzodipyran derivatives

Tttr&&m

Prinwd

Val

44. No

Brium.

m GUI

15. pi. 4857

lo

4862.

I988

oo4o4ozo/l?8 53.00+ 1x) 0 1988Rrpmon Pra pk

CATTOWRADICALS IN TIIg BRCMNATIOWOF BlW.ODTPYRANDWTVATIVES

FRANCIS U. DEAN, STEMN N. FRANCI and UIXU OY?4AN

The Robert

Robinson

Laboratories.

LIverpool,

University

of Liverpool

L69 38X, U.K.

in UK

(Rrcrivrd

17 hfay 1988)

the free armtic lftu in 2,3.4,7.0.9-huaAbstract - Bromim attacks hydro-2,2,7,7-tatruthJl~nxo[1,2-~:4,5-~’~dipJr~ and its an&m isomer 1,2,3.B.9.10-huuhydro-3.3.8,B-tat~~thylknro[1,2-~:4,3-~‘~dipyr~ ulthout clur widanca for the intwudiacy of cation radicals. Uhan tlu nuclur situ ara rthylated [as in
on the

indicated 5.

that

‘H fpr

Bowsvcr , the athod

and the

conuquant

connected

line

broadanlng

in tha dwlvad

cation

is

open to

broadening

by a tr-irslon

not known and =ilht

raducc

problu

relatfvaly

slppl~

mthylans

in

(chr-)

tha

nucleus.

WC lava spectra other)

signal

that chxnpa

because

of

can

considered

For tha llnur

for

(2)

P.HL’

(4)

x.

en3;

4857

or

dcrlvativu tha starred

the broadening

121

spin

methyl groups

attached

(_3J R.H (iI R . &

of rthyl

to

the

and its

derivativu

of

at position

spln

at any lroutic athylsns

and rthylana

compound ia altered

and vharc u

(1)

concantratlon

the effect

benzodipyran

s-try Iscrsr

so-

an attached

If tha typa of the

6-hydroxychr-

vu that

fror

1s diffcront

-ined

be

of

there

the objection

tha

factor

ia gasrally this

in

in spectra

radicals

are

groups.

but

substmtially.2

(2)

and

(2)

groups

(methyl

S-position

in

of the aroutlc

site

group

which in one a

To haw and

bantopyran

methyl groups

is

F. hi. DIXN et al,

4858

17.8 Hz under

misslon groups will

specified

the

Simllsrly.

fsctor snd

b

conditions,’

methylena

2.9

groups

TCh2.

For

Hz for

the

muc!~ the

s”.

for

linear

and angular

the

the

(1)

h4s

brosdened

4npulsr

mthylene

for

5 of the chroman nucleus

4nd this

4re

isomer

(2)

groups.

two structures.

then

is

4wnsd

From this

it

elsewhere

in the 6-hydroxychraun

suy vsry

over

sevor41

In order such

to determine

compounds ve

benxodlpyrsns

h4ve

snd raav41

bromine

in

is

bellovod

With

bromine study

but

4cld

it

re4ction the

uln

peroxide

4

rust

view

in

of

the

methyl f4ctors

at

position

the expressions

the fsct

of

c4tlon

regenerstes solid

might

st

tribrollde

origin41

thy1

hss

series

4s

benrodlpyrln

be

no

with

bec4use

if

snd

the

solid

substitutions

too

reduced becsuse

fully

derivstive

but

th4t

msny

unst4ble

for

rull4tsly

by

iodine

bromide

(2).

Further

vhlch Light

(fi).

nuclesr

respectively.

dlbrcaiod4te

snslysed

of

With

fro4

4nd (1).

4 brovn

of

further

lnt4ct.

recut

benrodlpyrsn

not been

to

(4)

(4)

chemistry

bro4dening

recognition 3 intermedistu.

ion

(8)

the

lloctrophilic

the

once 14ve

ch4r4ctcrissble thst

5 thsn

In thls

sub4trste

4nd

be siqle

h4ve r4dic41

r4dicsl

rudily

position

llne

s-

the

(2)

4ml of

(2)

4 mixture blsbr-

4nd le4ves

dlpyr4n

the

4t

the

there

derlv4tives

results

4ctu4lly

but

dibrao

ructions

other

induces

derivstlvu

the

spin)

brosdenlngs

would 4ffect

Iodine

iodine

benrodipyr4n

thst

distribution

forutlon

the

giving

1.99

14 s mfnor one.

spln

r4dlcsl

raoves

ionic

be the

the

little

bier

methyl4ted

sffords

constituent hsve

in

brown

brcmlne

7 by combining

more unpsired

(i.e.

in view

the effect

snd the

noted,

msinly

simil4r

with

the

the fully

sscorbic

this

slso

to be purely

dotslled

produces

solvent

~4s

but

cation

of

unlikely

for

x TM,,

soms h4logenstions.

brcmlnstsd

st4go

this

re4ctlons

whether

Mistsly

No lntermsdl4to elthough

nuclei

totr4chlorasOune

sre

3.6

is more brosdcning

uulned

of

x Ta2

of qInltw.ie

ch4rscterlstlc

resction

positions

there

orders

Hz

trsnsmlssion

2.9 x T(-Jj2 =

7.2 thst

3.6 the

thus:

17.8 x Tn,

sppe4rs

sr4

Tl,e.

by 4 tr4ns-

out when the effects

position

at

fsctor

be modified

th4t

cancel

they

tr4nsmisslon

h4s to

brosdenings

it

those

by s

AZ vhlch

the

If

are compared 4th

isomers

to be modified

by 7.2

contsins md

4s

benxoyl

effect.

Scheme 1 The

structure

spectru

(Tsble).

species

depicted

spin

distribution

4ccepts Scheme.

braidc It

is

of

the

thy1

blsbr-

Scheme 1 outlines sre in ion lass

of (IJ) snd .4sy

course In

formulstc

steps

(a) th4t

systeu vith

4ccMd4n~4

sromstisbs. to

the

delk4llsed

product

our

Two sep4r4te .

credible

is ve in

cle4rly

consider

with

s

The’interndlste

brominstloas route

by 4nslysls

to underlie .but

rulity,

srgumsnt.

defined

throunh

l re

required

.%@ssn.

this hiss is

4nd nmr

result;

the

in chsrge

snd

(E),

sccording bismethide

vhich to

this

slthouuh

Brominstion of bcnmdipyran derivetires onto

this, occur

of

uck

bulky

tuo hydropen etou on the

therefore

We nest msthyl

bromine

1ore

or

exemfned

nsin

(fi) ves

of

69%.

At first et

the

group8

with

either

When bromine

itself

this

the

is

remein

not

es

this

intormedfatt

msthide

cesa

and then

either

cetfon-redicel product Teble,

structure

to

2 shows the

the

one

Schw

shift

thet

Siailsr

operations

the

ArH

(220 If%;

ArCH3

2.06 2.08 2.05 2.09 2.12 2.07 2.08

CDCl,/‘MS)

eech

is

fnitiel.

e

product If

then the yfold

for

uncoupled

vould

attack

loss

the

spfn

is still

hydrogen

with

the other

of

or. side

of Bcnrodlpyran

group

bond ten

there

1.72 1.78 1.80 1.80 1.77 1.76 1.87 1.78

6.91

2.66

I.76

1.50 1.50 1.56

first

atege.

explrfned,

end the

CH2Br

4.61

4.52

but

intermedfete e

for

qufnone

aromstfcity.

be bromineted

6.94 6.87 6.87 6.95

in sol occurred

giving

Derivatives

2.67 2.55 2.76 2.54 2.61 2.54 2.81 2.59

k

can be tfms

of the molecule

BrC:CIJ

tuo

is about

concentrations

more probsbly,

ArCILffi2 p&40

(Is),

et the methyl

in the

a proton

ArCHpI

1.28 1.28 1.31 1.31 1.27 1.28 1.35 1.27 1.50 1.51 1.28

eech

the sums key ion

end

the

uplsnetfon

ion es elresdy

methyl

the double

reection

bromineted

(z).

where br~ine/bromide

first

tstrschlorothe bisbromo-

by &rens 4 system. The

(14). 1 H NH8 Spectra

is

located

similer

but no other

beginning

regenerates

at

tha doubly

of much broalde

in which

of

in

nono of

component

that

raectfon absence

method

end dchydrogenatod

first

in bromide

reection

yield

bromine ves

abstracting

is rich

substitution

usuel

and closely

groups

radicals

showing

chromene nucleus

en eloctrophflic

sequence.

in the

it

the remaining

(45% by ‘If omr anel-

conteined

efficiency,

rthyl

fmidoyl

the

proupr;

the

eppeerences,

selective

roplecment

leaving

the

was essigned

our view

arovtic

but

by

brominerod

beve the ssm

the

sfte

similar.

but it

a published

into

after

the

hydropeu etom csn

l

of selectivity.

ethyl

singly

it

the misturo

reaction,

e prototropic

through

to

the !j-bromotucciniride

6.48 6.58

-

or

Schwa

chengo,

provides

be the

deeptte

etoms

for 5 _

wry

resulted,

to contredict

is the rea8ent

in the bromine

The sequence

to

converted

the ltteched

brafne

low in solution

(g)

reference

route

36% by isolation

degree

aromatic

remove1 of

plene;

l re

constituents

with

found

assumed that,

to ue so we have

mfrture

preferred

uuructive.

about

e moderate

intact

eppeered

with

is

our thet

out-of-plene

by g-bromosuccinlmide

sequences

result

the pointa

up the

of two ufn

which

dohydrogonetfon-brominetive

the eroutlc

brominetions

with

(Teblo)

constituent

to take

end relatively

two

s complex

‘Ibe firnt

structure

treetmnt

excess

will

In

from the fact

compound (a)

the

braafnation

the ‘fi nmr spectm

further

tbet

in-plenm

that

Agefn

compound (lJf.

other

Q$

product.

follove

60X end 67X indicating

heating.

dehydrogenated

l tom

less

assurptfon

betveen

methane with

(20)

correct

the group

of bfsbromms thy1

The yield ysfs):

(Q)

give

nthyl

only vheu the Clf bond 18 perpendiculer

the reletfvely

of

would

produced,

~brarfnetion

4859

through give

pivfng another

the

other

F. hf.

C)MN?I of.

rcr (2) Scheme 2 In theory, product (a)

therefore,

containing

Y~B unmsnakvablo.

brmine

should halogenate the aromatic ~~tbyl

four bromine atas

M could alto

Howwer ,

these methyl sroups nov that prototropfc fact

to obtain

the product (16)

vlth

succlnlmlde should not d&dro~mata methyl groups bar the chief and the mixture produced The mpular

additions

etc.

ltcae

in fret,

mode of attack;

plve

dehydrogenated products

with

the view

reacted

(19)

and (a),

wuwltlvity

(badly)

in this

there

1s sm

Schema 3 continues the pravious argunnts

and ve vore able in

readily

g-bravo-

because the brm-

rvectlon

and (~11)

nov be at

and also discloses

halo/en at

Contrarlvlso,

methyl groups

will

glvfnp a

but lt

fs carplox

compound (16).

with braine

attack

way.

collpound (lo)

tha wometic

to radical

to Introduce

are no longerpossible,

brains

the biabr awrrthyl

(2)

groups of (ik)

competed and the product

expect I?-brcmsuccinirlde

shifts

four

in practice,

appears not to contain the tetrabrcwo

benzodipyran that

but,

with succinimldo

rurvlvlng

the ring

that the wgular

lo

to

a#r”urt

rthylem

groups.

arrangement

cp) Scheme 3 of

the intsrndiotc

which will which

a

cation

therefore quinone

controlled. at position the cationic

uethtde

Consequently,

formmtlon, (Ii)

(a)

permits

be energetically all

our

rssults for

uinly

by tb

to (lQ1

therefore

view

can be explalnod radical,

by a single

proton

than the lroutfsation

hydrogen abstraction

5 of a b-hydroxychroman cationintermediate

arautfratioo

Uu can

intervenes.

a modest preference

full

mora favourable

and (til)

ease of transformation

tlw

outcae

by (il

initial

from ‘roups kinetic into fully

shift,

in Schrrr as

(wthyl control arcutlc

2 in

kinotlcally

cation

radtcal

or methylem) of

the f&o specfos.

of

Brominrtion of benxodlpyran derivativa

4861

(4). S,lO-~ibr~-2,3,4,7,8.9-~dro-2,2,7,7-t.tr_thyl~[l,2-~:4,S-~’jd~~vr~ Brain. (0.2 ml) in totr.ch1ormth.w (20 ml) vu .dd.d to 2.3.4.7.8~hushrdro-2.2.7.7%tr.m.thylb&rol.l,2-b:4.5-b’1dipyr.n (254 s) .lso In tetr.chloro_hur. (50 ;l) during 10 min. Aft.r 4.5 h, .lr w.s blown Thor. vu UI tidi.to &rk.nlnl of colour but no pr.cipft.t.. th. solution w.‘ then wshod with through the lolutlen tmtll .ll free brain. hd be.n r_ved; then sodfu hydtotm c.rbon.ts solution, .nd fin.lly vith .qumus sodiu hyvlm eulphito, w.t*r. Th. dried selutlon _ concentr.ted under V.CUU Iewing . clur _ tht wes subjected Throm fr.ctfons w.re obt.ined. to purffic.tion on silic. with hu.zm-tolwn. (3:l) .s elu.nt. th. first .nd third consisted of rixturos .nd were not exulnod furthsr; the second (Rf 0.28) supplied

the dibraoh.uhrdrobeasodlDvr.n

(from methanol), cm-* (yound: C. 47.55:

v_.

C. 47.6;

5.0X);

2 959. 8,

1 432,

l4. 401.983

5.0X.

I$ 401.983

ss

2 918,

00,

403.981

03,

rectmgulsr 1 409, 00.

p1.t.s

1 365.

403.981

405.979

(233 mg; 56X),

1 312,

03.

1 179,

405.978

m.p.

1 155,

91 0.

160 -

960,

900,

C,6R20Br202

164.C

.nd 828 requires

06.

(7). 5.6-Dibrm-1,2.3,8,9.10-~ydro-3,3,8,8-t.tr~thyl~zo[1,2-b:4.3-b’]dl~yr~ 1,2,3,8,9-Hu~ydro-3.3.8,8-t.tr~thyl~nso~1.2-~:4.3-~‘ldlpyr~ (254 w) v.s treated vlth Chrcmatogr.phy with hex.ne-toluene (1:l) u brain. (0.2 ml) .s in th. foreping experiment. llwt furnlsh.d two fr.ctions of which tbe first e.s . mixture uui vu dlsc.rded; the second (Rf 0.34)

c0nsist.d

169’C

(from

167.

1 120,

of

the

dibr_hu.hvdrobmswlodoyr.n

mtiunol),

vlyx

1095,

918,

962,

2 965. 899.

2 937,

895.

fomlnp

2 920,

1 430,

.nd 832 cm-’

prisu 1 410,

(Pound:

(283 1 379.

C, 47.8;

mg;

68X).

1 365,

H, 5.1X;

a.p.

1 328.

167 1 238.

I$ 401.983

1

022.

C16H20Br202 requires C, 47.6; 8, 5.0X; F4, 401.983 00. 403.981 03. 403.980 956. 405.979 810. 405.979 06). 5.l0-~(braorthtl)-2.3,4,7,8,9-h.x.hydro-2,2,7,7-totruthylknro~1.2-b:4,5-b’Jdlp~.n ml) in tstr.chloraeth.ne (50 rl) vu .ddod to 2,3,4,7,8,9-hcx.hydro(lo). - Bromine (0.8 2,2.5,7,7.10-hexuthylbensoi1.2-b:4,5-b’1dlpyr.n (1.4 g) .lso In t.tr.ch1orcaeth.w (150 ml). The colour d.rkur.6 .t onto snd . brown solid sep.r.ted which decomposed with evolution of When left --in situ vlth stirring for hydr0g.n bromide when .ttapts wr. mad. to isol.tc It. 4.5 h the solid redissolved .nd the r..ction mixture V.S work.d up in the mnner descrlbod .bove except th.t, .ft.r r-r.1 of solv.nts. the residue V.S p.rtly solid .nd. inste.d of Wdl.te chromatogr.phy, u.s v.shed with hot hox.ne .nd then cryst.1lis.d from trichlorometh.ne giving the bisbrororthylh_hvdrobenrodIpvr u1 .s f.lntly yellow prisms (728 mg: 33X). m.p. 235 24O.C. v 2 980, 2 920, 2 868. 1 466, 1 424. 1 418, 1 371. 1 362, 1 278. 1 263. 1 242. 1 220. 1 201. 430.014

1 125,

l?O, 024,

432.012

1 110, 256,

996.

974,

434.OLo 210.

953,

887,

655,

.nd

545 co-l

C18R248r202 requirea

(Found:

C, 50.0;

C. 50.1;

ii. 5.6X:

H. 5.6X;

n, 43C.014

i.

28.

432.012 31; 434.010 34). The su compound w.s obt.ined by using 2,4,4,6-tetr.broaocyclohex.-2,5-dlenone lnstud of brorin. md with trlchloracthuro as solvent, .nd lncludinp sn .lk.line v.sh to rmove phenollc products. However, it proved difficult to remvo non-phanollc side products urd the re.ction w.s not studlod furth.r. 3,8-Dibrow-2,7-dlhydro-2,2.5,7,7,10-hex.nth lbnco-[1.2-b:4,5-b’1dfpyr.n (6). - 2.3,47,8,9-Aex.hydro-2,2,5,7,10-hox.m.thylbenzo 1dlpyr.n (1.4 g) .nd N-brcmosuccinlmlde A 1,2-b:4,5-b Air w.s blown (2.7 g) were h..ted together in refluxlng tatr.chlorowth.ne (150 ml) for 24 h. throuph the solution for 20 min., .nd th.n the succlnimlde produced w.s filtered off and the ffltr.te v.shed, succ.sslvely, with .queous sodium hydro8.n sulphlte. .qu.ous sodim hydrogen c.rbon.te. .nd w.ter. 5%. residue left .fter drying .nd ev.por.tlon of the solvent w.a chroutogr.phed on sflic. wing hexure-tolune (4:l) .s llu.nt. The first fr.ctlon cont.ined . mixture not ex.mlned further. The second fr.ctlon (Rf 0.33) supplied 3,8-dlbromo-2.7-dihvdro2,2.5.7.7,lO-h.xsaethvlbenxo~1.2-b:4,5-b’]dlwrsn thick

prisms

1 140.

1 007.

429.978

91.

the

(634 mg; 29X), 872,

855.

.nd

m.p.

193 -

817 cm-’

C18R20Br202 requires

which 199’C,

vmx

(Pound:

C. 50.5;

4.7X;

s0p.r.t.d

2 970.

C. iO.6:

8.

!4, 425.983

The next fr.ctlon cont.ined this c-pound with .nother other (Rf 0.21) which Y.S obt.ined .a . roft gum th.t

3-~-2.7.8.9-t.tr.h~dro-2.2.5.7.7.l0-hex_th~lknxo[1.2-b:4,5-b’Jdi~~rur

2 950. 4.9X;

from

hex.ne

2 910, fi,

CO, 427.981

425.980 03.

ss

p.le

1 449.

1 353.

02.

429.979

.s

1 267.

427.900

95.

06).

.nd l.ter fr.ctions cont..lned cryst.lllsed from 2-propmol (2)

yellow.

prl_

only giving (484

19; 27X). m.p. 92 - 94’C. v_. 2 965. 2 938. 2 920. 1 367. 1 358. 1 275. 1 168. 1 147, .nd 970 _, -A (Pound: C 61.7. H 6.6X* If 350.085 06, 352.006 75. C18R23Br02 requires C, 61.5; H. r6X: If. 350.08; 07. :52:086 Id).-’ _2,9-Dibroro-3.8-dihvdro-3.3.5.6.8,8_huutnso[l,Z-b:4,3-b’ldlpvr .n (21). - (i) Bromin.tion by brain.. Bromine (0.2 ml) in tetr.chloraethure (20 al) w.s .dded-Tb 1,2,3,8.9.10h~ydro-3,3.5,6,8.8-h.x_thyl~zoI1,2-~:4,3-~’ldipyr~ (306 mg8) .lso in tetr.chloromethure (30 ml). 4s with the ben~o11.2-b:4,5-i’1dipyr.n lsowr .bove. a d.rk colour .nd brown pr0cipit.t. wt. observed. md After 4.5 h .t roa tuper.ture the mixture w.a worked-up in the ‘U v.y. R.cryat.llis.tion of the crude product frcm trlchlorometh.ne failed to give pure ruterl.1 so it w.s chr_togr.phod on silic. gel using h.une-tolune (3:l) .s .lu.nt. After r-v.1 of 111 lnitl.1 fr.ctlon cont.lning . mixture (not .n.lysod further) . main fr.ction Y.C secured th.t cont.in.d . single subst.nce (Rf 0.48) which sep.r.ted from rthurol to give the

4862

dibroaodihydrobanrodiuvrsn 920,

1 373.

1 351.

ss

1 275.

irragulsr

1 141.

1 333,

F. M. DEAN

lI d.

prims

5;

(62

1 095.

13X),

snd 875 as-l

x.p.

137 -

(Pound:

140Y,

C, 50.5;

v_.

2 965,

B. 5.0X1

427.980 956. 429.987 910. C181i2UElr202 requires C, 50.5; H, 4.7X; I$ 425.913 00, 429.979 06). Subsmqwnt frsctions contsined both (2l) snd snothar substsnco which lster sppurmd This mstarisl crystsllismd fra vat uthsnol aivina Z-w-3.8.9.\0-a sad hsd Rf 0.33.

02, 03.

84.C.

“_.

1090.

2 967.

918,

(20)

thlknsol1,2-b:4,3-b’ldi~~

--3,3,5,6,8,8-h-

2 9300. 2 910,

snd 870 cm-1 (Pound:

2 890.

2 840,

C, 61.5;

1 441,

H, 6.8X;

..

1 378.

plstu

(137

1 355.

l& 350.088

14.

5;

1 271,

352.086

35X).

1 164.

2

I& 425.983 427,981 slonr

r.p.

1 147,

80 1 118,

10.

ClaB23Bx02 , 350.088 07. 352.016 10). (ii) Brainstion by N-brarosuccipUdm. mquiras C. 61.5; H. 6.6X; with W-broxosuccinirid~ (2.7 a) in rafluxlna The raquisitm bnzodipyrsn $ 6) (1.4 a) vss hutad tetrscblorarthsnm for 24 h snd ths products umu isolstad ss in the preview ructicm with this rssamt. Chromstoarsphy supplied the dibrmbenrodlpyrsn (929 ng; 43X) snd the mobraobuuodipyrsn (376 mg; 21X) Identicsl vith ssmplos obtsined by tha we of brain@. lbmoso[l.2-b:4,5-b’]dimrsn 3,8-Dibrm-S,lO-bis(br-thrl~-2,7-dihvdto-2,2,7,7-t~tr~~ - Tha 3,8-dibrorobmro[l,2-b:4.5-i’ldipyrsn (14) (1.8 a) VU hutd vith W-brmmccin(6). iride (3.3 a) in tetrschlorasthum for 24 h snd tb products isolstd u in other such hslo/mations. Tha crude product vu psrtly soluble in husns-tolwne (4:L); thm inrolubla psrt sspsratad fra husna to pivs thm 3,8-dibrm-S,lO-bis(browrwthvl)knz~~D~M ss stout ymllou prisms (932 q; 35X), r.p. 197 - lPQ’c,_. 2 970, 1 420, 1 280. 1 195, 1 133, 1 123, 989. 851,

sod

589.795

631 84.

cm-l

(Pound:

C1aHlaBr402

C. 36.8; requires

A, 3.2X; C. 36.9;

l$

581.804

H. 3.1X;

02,

583.801

!4. 581.804

14,

98,

585.799

583.802

17,

93,

587.797

585.800

89.

20,

587.798 23, snd 589.796 26). Chrcmstoarsphy supplied s further qwntity of this coxpound snd slso frsctiona ccntsinina mixtures thst v.re not lxuinad further. 2.3,4,7.8,9-Huuhydro-2,2,5,7,7,lO-huuuthvlknro[l,2-b:4,5-b’]dipyr~(l+) - The linear huxsmthylboncodipyrsn dsrivstiw (2) (2.9 a) in totrschloraothsna W 200 xl (9). A pracipit8to fornd wss trastod with iodina(I) broride (4.2 p) in the ssms solvent (200 xl). Nltroaur rspidly snd did not rodirsolva .vmn on stsndina for scms hours in diffwe dsylight. YU blown through the mixture to r-v. frao hsloaens, then thm solid vu colltid by filtrstion snd wsshad vith tetrschlorathsne snd dried In vscuo, losvina the dibrcmoiodsti u s dsrk green-blsck microcrystsllina povdor (3.9 a, 65X), B.P. 19O’C (dacomp.), v_, 2 960, 2 915. 2 905.

2 840,

snd 808 cm-’

1 423. (Pound:

1 399,

1 370,

C. 39.0;

8,

1 340, 4.7.

1 327,

1 293,

C1aE26Br2102

1 222.

requires

1 151. C, 38.5;

1 099, 8,

1 079,

4.7X).

1 011,

918,

The usa

spectra uhibitmd s psrmt puk for the ution st p/z 274.193 28 (ClaR2b02 requires B/R 274.193 14). Attupted recrystslliastion docapoacd the compound. The hsloaan could b moved snd the c&ion rsdicsl reduced by sqwow sodim rtsbiA solution of the sulphite. sacorbic scid, of sodim thiosulphsto; the lsrt vss tha best. c&ion rsdicsl sslt (555 -0) in dichloroauthsna us8 rhskm for 72 h with W_-sq_w sodim Thhs orasnic lsysr vss wsshd vith ustar. thiorulphsta until sll the colour hsd dissppasrsd. This v.s identified with the haxsdrid, snd concentrstsd until s solid reaidw rsuinad. msthylbanzodipyrsn (2) (260 mg; 96X) by spctroscopic snd other umns.

snd

The suthors thsnk I.C.I. Phsnucouticsls

the

Turkish Limited

AcKNmLEDGRmm Cove -t for flnsncisl for s CASE studentship

support (S.N.?.)

(U.O.)

snd the

D.8.S.

(U.K.)

REFERENCKS

1. 2. 3. 4. 5.

I. Al-Khsyst, P.M. Dun, S.N. Prsnco, D.A. h&kin, h.0.A. Orsbi, I4.L. Robinson, R.Y. Turrmr, snd R.S. Vsrms, J.Cha.Soc., Perkin Trsns. 1. 1985. 1301. C. Vlncow, in “Rsdicsl Iona” ed. B.T. Ksiser snd L. Kevan. Interacionca, 151 (1968); J.K.H. Ssndars. C.G. Newton snd J.C. Ustarton. J.Hsn.tia.. 1978. 3i, 49. J.P. Bunnctt. J.Cha.Ed.. 1974, 5l. 312; N. Kornblux. Anneu.Chrr.Int.Ed., 1975, l4, 734; E.C. Ashby. A.B. Coel, snd J.N. Arayropouloa, Tetrshodron L&t., 1982. 2273. 1971, 104. 168. B. Bofunn snd C. Sslbck, Cha.&r., P.S. Skull. J.C. Dsy. snd H.J. Lindstrca. J.k.Chr.Soc., 1974, 96. 5616.