Synthesis of photochromic spiroindolinopyrans with extended conjugation

Tetrahedron, Vol. 52, No. 26, pp. 87554162, 1996

Copyright 43 1996 Elsevier Science Ltd F’rinted in Great Britain. All rights reserved 0040-4020/96 $15.00 + 0.00

PII: S0@40-4020(96)004 16-4

Synthesis of Photochromic Spiroindolinopyrans Extended Conjugation

with

Sharmila. K. Thakur and Bhaskar. D. Hosangadi* Department of Chemistry, University of Bombay, Vidyanagari, Bombay - 400 098 INDIA. : Unsaturated side chains have been introduced in benzopyran site of parent indolinospiropyran moiety using Wittig reaction under conditions of Phase Transfer Catalysis in a one pot synthesis. The resultant unsaturated photochromic indolinospirobenzopyrans show significant bathochromic shift in the uv region of absorption spectra. Copyright 0 1996 Elsevier Science Ltd Abstract

In past, Wittig reactions either NaOEtt

or NaOH in DMS02.

reverse photochromism3

indolinospirobenzopyrans

Since indolinospirobenzopyrans

have been carried out using

exhibit thermochromism

as well as

in presence of even mild organic acids, like malonic acid or Lewis acids, like SnC14,

reaction conditions eliminating

SCHEME

with photochromic

the use of acid and thermal conditions were envisaged.

[Scheme - 1]

1.

Phase Transfer Catalysis (PTC) which satisfies these requirements for the first time for this class. Quaternaty

was adopted,

and is being reported

ammonium salts using bases like KOH, NaOH, K2CO3, Na2C03

have been used, but these reaction conditions

riced rcfluxing and during work-up

procedure

use of acid is

essential. We now report a method using phase transfer catalyst, namely l&Crown-6 indolinospirobenzopyrans.

for Wittig olefination

This method is of significance as reactions are carried out at room temperature 8755

of in a

8756

S. K. THAKUR and B. D. HOSANGADI

one pot synthesis. The Wittig olelination gave comparable

was successfully

attempted using two different routes. Both the routes

yields (25 - 28%).

In the first approach

1’,3’,-dihydro-6-formyl-

1’,3’,3’-trimethylspiro[2H- 1-benzopyran-2,2’[ lH]indoline]

i.e. 6 - formyl BIPS (5) was prepared by reacting Fischer base (4) and 5-formyl salicylaldehyde treated with phosphonium temperature.

salt of aIky1 halide in presence

of anhydrous

(3). It was then

K2CO3 and l&Crown-6

at room

[Scheme - 21

SCHEME 2.

R

C-H “c”ol”fJW aq. “cl

OH 1

2

In the second methodology, gave corresponding phosphonium

5chloromethyl

phosphonium

salicylaldehyde

(2) on reaction with triphenyl phosphine

salt (8). The latter on condensation

salt (9). Without isolating this intermediate

presence of anhydrous K2CO3 and l&Crown-6

with Fischer base (4) gave a Spiro

further reaction with different substituted aldehydes in

in CH2Cl2 was carried out. [Scheme - 31

SCHEME 3.

2

+

PPh2

-

C6H6 A

7s. b, f - k

Photochromic

8757

spiroindolinopyrans

Table 1

1H NMR (CDClq) S ppm

i,l

1.2 (s, 3H, Me); 1.3 (s, 3H, Me) ; 2.8 (s, 3H, N-Me); 5.8 (d,lH,C4-H); 6.4 - 7.8 (m, 15H, Ar-H & C= C-H)

a

1.2 (s, 3H, Me); 1.3 (s, 3H, Me) ; 2.8 (s, 3H, N-Me); 5.8 (d,lH,C4-H); 6.4 - 8.0 (m. 14H, Ar-H &C=C-H)

b

1.2 (s, 3H, Me); 1.3 (s, 3H, Me) ; 2.8 (s, 2H, CH2-Ar);

IR (Ur) cm-l

UV (EtOH)

cm-* 960 (Cspiro O), 1650 cm-l (C = C-Ar)

316nm (E 33620)

960 cm-’ (Cs iro - O), 1520 cm-l (-402).

386nm

1650 cm-* (C = C-Ar)

(E 33000)

960 cm- 1 (Cspiro - 0)

294nm (E 13880)

2.8 (s, 3H, N-Me); 5.7 (d,lH, C4-H); 6.2 - 7.6 (m, 15H, Ar-H, Q-H and HC = CH) 1.2 - 1.6 (m, 9H, Me); 2.8 (s, 3H, N-Me); d

ii --c-OEI

4.2 - 4.3 ( q, 2H, -OCH2); 5.8 (d,lH, Cq-H); 6.2 - 7.8 (m, lOH, Ar-H, Cq-H and C = C-H) 1.2 (s, 3H, Me); 1.3 (s, 3H, Me);

e

2.8 (s, 3H, N-Me); 5.8 (d,lH, C4-H); 6.4 - 7.8 (m. 15H, Ar-H, C3-H and C = C-H)

-

Compounds

7a and 7b were synthesized

and Cnitrobenzaldehyde

respectively

Further experimental under investigations.

970 cm-l (Cspiro - 0), 1250 cm-l (O-C), 1720 cm-l (for ester)

317nm (E 25000)

960 cm-l (Cspiro - 0).

331nm

1660 cm-l (C = 0 of keto)

(E 39300)

by this pathway using phosphonium

salt (9) and benzaldenyde

and they were found to be identical with those obtained by first route.

studies on photochromic

properties

of newly synthesised

Spiro compounds

are

8758

S. K. THAKUR and B. D. HOSANGADI

Table 2

R

7

1H NMR (CDCl3) 6 ppm

IR (KBr) cm-’ h,,,

1.2 (s, 3H, Me); 1.3 (s, 3H, Me) ; 2.8 (s, 3H, N-Me); 5.X (d,lH,C4-H); 6.4 - 7.8 (m, 15H, Ar-H & C= C-H)

a

1.2 (s, 3H, Me); 1.3 (s, 3H, Me) :

b

u- \

/

l@

2.8 5.8 (s, 3H, N-Me): (d,lH,C4-H): 6.4 - X.0 (m, 14H, Ar-H & C = C-H)

960 cm- ’ (C Spiro - 0). 1650 cm-l (C = C-Ar)

run

316nm (E 33620)

960 cm-l (C, ire - O), 1520 cm-l (-802).

386nm

1650 cm-1 (C = C-Ar)

(E 33000:

____________

(E 36140)

1.17 (s. 3H, Me); f

I .29 (s, 3H. Me);

-

-o\

/

Y’

2.3 (s, 3H, Ar-Me); 2.7 (s, 3H, N-Me); 5.7 (d, 1H, C4-H), 6.4 - 7.7 (m, 14H, Ar-H, CT-H & C = C-H) 1.2 (s, 3H, Me); 1.3 (s, 3H, Me); 2.7 (s, 3H, N-Me): 3.8 (s, 3H, OMe): 5.6 (d, 1H, C4-H)

317nm

960 cm-’ (Cspiro - 0), 1260 cm-l (-O-Me), 1650 cm-l ( X = 0 of ketol

319nm (E 37660)

6.4 - 8.0 (m, 14H, Ar-H, Cq-H & C = C-H). 1.14 (s, 3H, Me): 1.27 (s. 3H, Me); h

2.7 (s, 3H, N-Me); 3.6 (s, 3H, O-Me): 3.8 (s, 3H, O-Me); 5.6 (d,lH, C4-H); 6.4 - 7.2 (m, 13H, Ar-H, C-+-H & C = C-H).

302nm 960 cm-l (Cspiro - 0), 1260 cm-l (-O-Me), 1650 cm- 1 ( >c = 0 of keto)

(E 20200)

Photochromic

-\/ 7o -d-

8759

spiroindolinopyrans

1.19 (s, 3H, Me); 1.28 (s, 3H, Me); 2.8 (s, 3H, N-Me); 5.8 (d, 1H, C4-H); 6.0 (s, 2H, -0-CH2-0); 6.4 - 7.6 (m, 13H, Ar-H, Q-H & C = C-H). 1.19 (s, 3H, Me); 1.28 (s, 3H, Me); 2.7 (s, 3H, N-Me); 5.7 (d,lH, C4-H); and 6.5 - 7.4 (m, 17H, Ar-H ) 1.19 (s, 3H, Me); 1.28 (s, 3H, Me): 2.1 (s, 3H, Me); 2.8 (s, 3H, N-Me); 5.8 (d,lH, C4-H) and 6.5 - 7.8 (m. 12H, Ar-H ).

960 cm-l (Cspiro - O), 1260 cm-l (-0-CH2-O), 1650 cm-l (>C = 0 of

363nm (E 23520)

keto)

960 cm-l 1660cm-1

(Cspiro - 0), (>C=Oof

342nm (E 31360)

keto)

960 cm- 1 ( Cspiro - 0 ), 1660 cm-l ( >C = 0 of

295nm (E 21700)

keto)

Table 3

EXPERIMENTAL

The compounds

were identified by 1H NMR, IR and uv spectroscopy.

Satisfactory,

microanalyses

also obtained (C, H, N analysis match with f 0.4%). Following chemicals used were prepared

were

according

to

S. K. THAKUR and B. D. HOSANGADI

8760

literature

methods;

base, 18-Crown-6

5-chloromethy1saIicy1aldehyde4, used were commercially

5-formylsalicy1aIdehyde4,

available products

phosphonium

sal&.

Fischer

from Fluka. 1~ NMR spectra were scanned in

CDCl3 on FT Brucker (80 MHz) and JEOL Fx 90 Q (90 MHz).

The IR spectra were recorded

on Shimadzu

Ff’IR 4200, UV spectra were recorded using Shimadzu UV- 16OA. All the melting points are uncorrected.

Condensation of Fischer base with S-formyl salicylaldehyde: 6-formyl-1’,3’,3’-trimethylspiro[2H-Ibenzopyran-2,2’-[IHI-indole]

i.e. CFormyl BIPS (5). Equimolar quantities of 5formyl

Fischer base (4) in ethanol (dry) gave the condensed water bath was decomposed crystallization

salicylaldeyde

(3) and

product. The reaction mixture after refluxing for Shrs on

in ice. The solid separating

out was filtered,

dried and further

purified by

from pet ether (bp 40 - 6OoC) mp 128 oC (lit6 mp 128 - Y oC)

IR (KBr) showed absorption

at 970 cm-l for (Cspiro0)

1680 cm-l for CHO

group.

lH NMR in CDC13 showed signals at 8 1.1’) (s, 3H, Me); S I .28 (s, 3H, Me); S 2.85(s, 3H, N-Me); 6 5.7 (d,lH,C4-H);

6 6.4-7.8 (m, 8H, Ar-H) and S 9.83 (s.lH, H of f
GENERAL

PROCEDURE

FOR COMPOUNDS

Equimolar quantities of triphenyl phosphine

)

7a-e USING METHOD-l

and alkyl halide were refluxed in dry benzene for about 8

hours. The solid separating out was filtered, washed with benzene and dried. I I mmoles of phosphonium

salt prepared as above were dissolved in 25ml CH2Cl2. To this 1 I mmoles

of anh. K2CO3, was added followed by 10 mmoles of 6-Formyl BIPS. To this 30 mgms of IX-Crown-6 was added and reaction mixture was monitored reaction combined

mixture

was filtered,

and concentrated.

chromatography

residue

at time

was washed

intervals with TLC (Pet.ether: with dichloromethane;

ethyl acetate 95:s).

washings

The

and the filtrate were

From the residual oil the desired product was isolated using silica gel column

with pet ether : ethyl acetate (982) as mixed solvent for elution.

Synthesis of 6-styryl BIPS (7a). 6-Formyl BIPS (5) was reacted with triphenyl phosphonium chloride (6a) as described in general procedure

given above.

salt of benzyl

The pure product obtained was crystallised from

pet ether (40 - 60 OC) white crystals mp 120 “C (lit1 120 - I oC) yield - 25%.

6-(4-nitrostyryl) BIPS (76). Reaction of h-Formyl BIPS (5) with triphenyl phosphonium bromide (6b) gave compound

6-(3-phenylprop-l-enyl)

7b. Yellow crystals,

BIPS (7~). Reaction

salt of 4-nitrobenzyl

mp 153 oC (lit’ 152 oC) yield 25%

of 6-formyl

phenethyl bromide (6~) gave compound 7c. Oil, yield 22%.

BIPS (5) with triphenyl

phosphonium

salt of

Photochromic

6-[2- ethyl

curboxy

vinyf]

6-[3-oxo-3-phenyl-prop-Z-enyl]

of triphenyl

benzene for 8 hrs. The solid separating phosphonium

FOR COMPOUNDS

phosphine

were

refluxed

in dry ethanol by refluxing for 6 hrs on water bath.

by distillation and phosphonium

11 mmoles of this Spiro phosphonium

salt (8) was used as such

salt (8) were taken in CH2Cl2 (50ml).

To this I I

mmoles of anhyd. K2CO3 was added followed by addition of 10 mmoles of aldehyde and 30mgms of Crown&.

The reaction mixture was stirred at room temperature

and monitored

ether : ethyl acetate Y5:5 ). The reaction was worked up following procedure

6-styryf BZPS (7~). Reaction of phosphonium

salt (9) with benzaldehyde

(lit’ 120 -1 OC). Yield 25%.

lg-

at time intervals by TLC (pet similar to that in Method-l.

After isolation from silica gel column, further purification was done by crystallisation

product with mp 120 oC

in

out was filtered washed with benzene and dried. 11 mmoles of above

ethanol was removed completely

for further reaction.

7f-k USING METHOD-2

and 5-chloromethylsalicylaldehyde4

salt (7) and Fischer base (1) were condensed

After condensation

salt of

7e. Yellow needles mp 106-8 oC. Yield 24%

PROCEDURE

quantities

salt of

7d. Light pink Oil, Yield 22%.

BZPS (7e). Reaction of 6-formyl BIPS (5) with triphenyl phosphonium

phenacyl chloride (6e) gave compound

Equimolar

8761

BIPS (7d). Reaction of 6-formyl BIPS (5) with triphenyl phosphonium

Bromo ethyl acetate (6d) gave compound

GENERAL

spiroindolinopyrans

from pet ether.

according to above proedure gave a

Spectral analysis of this showed that it was 6styryl

BIPS (7a) as all data was in agreement with that of 7a obtained from Method- 1.

6- (4-nitm styryl) BZPS (76). Reaction of 9 with Cnitrobenzaldehyde identical to 7b obtained via Method-l.

6 - (4-methyl

sfyryf) BZPS (7f.

gave compound

which was found to be

mp 153 oC (lit1 152 OC) (Yield 25%)

Reaction of 9 with p-tolulaldehyde

gave compound

7f.

White-pale

yellow

crystals. mp 126 - 8 oC, Yield 24%.

6-(4 methoxy styryl) BZPS (7g). Reaction of phosphonium

salt (9) with anisaldehyde

gave compound 7g.

Yellow needles mp 166 oC Yield 24%.

6-(3,4-dimetholy veratraldehyde.

styryl) BIPS (7h). Compound Yield 22.X%.

7h was obtained by reaction

of phosphonium

salt 9 with

S. K. THAKUR and B. D. HOSANGADI

8762

6(3,4-methylenedimy

sty@) BZPS (7i). Phosphonium

salt (91 and piperonal

gave compound

(7il. White

crystals mp 120 - 1 oC. Yield 26%.

6-(4-phenyl-but-Z,fdienyl)

BZPS (7j). Compound

(7j) was obtained from reaction of 9 with cinnamaldehyde.

White crystals, mp 126 oC. Yield 28%.

6-(penta-Z,3-dienyl) BZPS (7k). 7k was obtained by reaction of 9 with Crotonaldehyde,

as an oil. Yield 22%.

REFERENCES

1. Braude, E. V. and Gal’bershtam,

M. A., Khim Get Soed, 1979,2,207.

2. Kakurai, T. and Takao, T., J P 61,490 [86-76,490]

1986 (CA, 10.5 : 208778d)

3. Shimizu, I.; Kokado, H. and Inoue, E., Bull. Chem. Sot. Jpn., 1969.42,

1726.

4. Angyal, S. J.; Morris, P. J.; Tetaz. J. R. and Wilson, J. Cl., J. Chem. Sot., 1950 2141. S. Le Bigot, Y., Delmas, M. and Gaset, A.. Tetruhedron., 6. Bertelson, R. C., Photochromism

1988,44,

1057.

: Techniques of Chemistry, Ed. Brown, G. H.:

Wiley : New York, 1971, pp 45 - 431.

*

(Received

Dedicated to Prof. A. B. Kulkarni on his seventyfifth

in UK 19 Februury

1996; revised 30 April 1996; accepted

birthday

2 May 1996)