Photochromic naphthopyrans containing a latent carbene unit

Article abstract of DOI:10.1080/15421400590946767

3-(Hydroxyalkyl)-1-naphthols 12 have been accessed in two steps from an isoquinolinium salt. The naphthopyrans 15, derived from 12, were readily diazoacylated with ethyl diazomalonyl chloride. The carbenoid generated from 16 failed to undergo any cycloadd

Full text of DOI:10.1080/15421400590946767

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Photochromic Naphthopyrans
Containing a Latent Carbene
Unit
Christopher D. Gabbutt a , B. Mark Heron a , David A.
Thomas a , Steven M. Partington b , Mark E. Light c
Michael B. Hursthouse c
&
a Department of Colour & Polymer Chemistry , The
University of Leeds , Leeds, UK
b James Robinson Ltd. , Hillhouse Lane,
Huddersfield, UK
c Department of Chemistry , The University of
Southampton , Highfield, Southampton, UK
Published online: 31 Aug 2006.
To cite this article: Christopher D. Gabbutt , B. Mark Heron , David A. Thomas ,
Steven M. Partington , Mark E. Light & Michael B. Hursthouse (2005) Photochromic
Naphthopyrans Containing a Latent Carbene Unit, Molecular Crystals and Liquid
Crystals, 431:1, 357-362
To link to this article: http://dx.doi.org/10.1080/15421400590946767
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Photochromic Naphthopyrans Containing a Latent
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3-(Hydroxyalkyl)-1-naphthols
linium salt. The naphthopyrans
with ethyl diazomalonyl chloride. The carbenoid generated from
undergo any cycloaddition and was instead intercepted by water to afford
1
2 have been accessed in two steps from an isoquino-
5 , derived from 2 , were readily diazoacylated
6 failed to
8 .
1
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K e y w o r d s : c ar b e n e s ; n a ph t h opy r a n s ; p ho t oc h ro m i s m
INTRODUCTION
T h e r ev e r si b l e r in g – c h a i n t a u t o m e r is m ( o r v a l e n c e i s o m e r i s a t i o n ) o f
t h e 2 H- p y r a n s y s t e m [ 1] h a s a t t r a c t e d c o n s i d e r a b l e a t t e n t i o n f r o m
a c a d e m i c a n d i n d u s t r ia l r e s e a r c h g r o u p s , p a r t i c u l a r l y w h e n t h i s s y s -
t em i s f u s e d t o a n a p h t h a le n e m o i e t y t o a ff o r d t h e n a p h t h o p y r a n i s o -
m e r s 1 a n d 2 [ 2 ] w h i c h c h a n g e f r o m c o lo u r l e s s ( p y r a n ) t o c o l o u r e d
( m e r o c ya n i n e ) ( S c h e m e 1 ); a c o lo u r c h a n g e p h e n o m e n o n k n o w n a s
p h o t o ch ro mi s m [ 3] .
A d d re s s c o r r e s p o n den ce t o B . M a r k H e ro n , D ep a r t m en t o f C o l o u r & P ol ym e r
C h e m i s t r y , T h e U n i v er s i t y o f L e ed s , L e ed s L S 2 9 J T , U K . E - m a i l : b . m . h er on @ l e ed s . a c . u k
5 7=[ 3 5 7 ]

5 8=[ 3 5 8 ]
C. D. Gabbutt et al.
S C H E M E 1
C o n t r o l o v e r t h i s d y n a m i c r i n g – c h a i n i n t e r c o n v e r s i o n c a n b e
a c co m p l i s h e d t h r o u g h c h o ic e o f s u b s t i t u e n t s o n t h e n a p h t h a l e n e u n i t
a n d geminal d i ar y l g r o u p s [ 2] a n d a l s o b y e x t e r n a l m a t r i x e f f e c t s
e . g . , s ol ve n t p o la r it y , 3 [ 4] p H , 4 [ 5] a n d m e t a l i o n c o n c e n t r at i o n , 5
[ 6 ] w i t h a p p r o p r ia t e l y s u b s t i t u t e d n a p h t h o p y r a n s . M o r e r e c e n t l y w e
h a ve s h o w n t h a t c a r b e n e s c a n b e u s e d t o i r r e v e r s i b l y o b t a i n m e r o c y a -
n i n e d y e s , e . g . , 6, f r o m n a p h t h o p y r a n s ( S c h e m e 2 ) [ 7 ] .
I n o u r p re l i m i n ar y c o m m u n i c a t io n w e d e m o n s t r a t e d t h a t t h e y i e l d
o f a n a p h t h op y r a n – c a r b e n e a d d u c t c o u ld b e m a r k e d l y i m p r o v e d b y
a d o p t i n g a n i n t r a m o l e c u l a r t r a p p i n g s t r a t e g y . T h u s r e d u c t i o n o f
n a p h t h o p y r a n 7 u s i n g L i A lH a t r t g av e t h e h y d r o x y m e t h y l c o m p o u n d
4
8 ( 6 3 %) ( S c h e m e 3 ) [ 7] . D ia z o a c y la t i o n o f t h e h y d r o x y m e th y l r e s id u e
w i t h e t h y l d i a z o m a lo n y l c h l o r id e g av e t w o n e w c o m p o u n d s , 9 ( 4 5 %)
S C H E M E 2
S C H E M E 3

Naphthopyrans Containing a Latent Carbene Unit
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a n d a n u n k n o w n s o li d , w h i c h h a s n o w b e e n c h a r a c t e r is e d a s 1 0 ( 3 4 %)
b y X - r a y c ry st a l l o g r a p h y ( F i g. 1 ) [ 8] . T r e a t m e n t o f a s o l u t i o n o f 9 w i t h
R h ( O A c ) i n C H C l g av e t h e t e t r ac y c l ic m e r o c y a n i n e d y e 1 1 i n 9 2 %
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W e n o w e x p a n d u p o n t h e s e p r e li m i n ar y r e s u lt s a n d d e s c r i b e t h e
s y n t h e si s a n d b e h a v io u r o f c a r b e n o i d s t e t h e r e d t o a 2 H- n a p h t h o [ 2 , 1 -
b] p yr a n u n i t b y e i t h e r a h y d r o x y e t h y l o r h y d r o x y p r o p y l l i n k a g e .
RESULTS AND DISCUSSION
T h e r e q u i r e d 3 - ( h y d r o x y a lk y l )- 1 -n a p h t h o l s , 1 2 , w e r e o b t a i n e d f r o m
t h e i s o q u i n o l in i u m s a l t , 1 3 , b y a t w o s t e p s e q u e n c e i n v o l v in g a
B r a d s h e r [ 4 þ þ 2 ]c yc lo a d d it i o n [ 9] t o a ff o r d t h e 3 - ( h yd r o x y a l k y l ) - 1 -
n a p h t h a l d e h y d e s 1 4 a n d a s u b s e q u e n t B a e y e r - V il l i g e r o x i d a t i o n
(ꢀ 3 5 % t w o s te p s ) ( S c h e m e 4 ). T h e n e w p h o t o c h r o m i c n a p h t h o p y r a n s
1 5 [ 1 0 ] w e r e o b t a i n e d b y t h e w e l l e s t ab l is h e d p r o p y n o l r o u t e [ 2 ] . T h e
v i s i b l e s pe c t ra o f i r r a d i a t e d ( 36 5 n m ) t o l u e n e s o l u t i o n s o f t h e s e c o m -
p o u n d s (1 5 ) e a c h s h o w e d t w o a bs o r p t i o n b a n d s ; a n i n t e n s e b a n d a t
c a . 4 9 8 n m w i t h a w e a k e r b an d a t c a . 4 1 5 n m . T h e h y d r o x y a l ky l
n a p h t h o p y r a n s 1 5 w e r e r e a di l y d i az o a c y l at e d (ꢀ 4 4 % y i e l d ) w i t h e t h y l
d i a z o m a l o n y l c h lo r i d e i n C H C l c o n t a in i n g 2 , 6- l u t i d i n e a n d a c a t a -
2
2
l y t i c a m o u n t o f 4 -d i m e t h yl a m i n o p y r i d in e ( D M A P ) t o a f f o r d a r e a d i l y
s e p a r a b l e m i x t u r e o f t h e d e s ir e d c a r b e n o i d p r e c u r s o r s 1 6 a n d t h e
c h l o r o - c o mp o u n d s 1 7 .

6
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C. D. Gabbutt et al.
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g a v e a c o mp l e x r e a c t i o n p r o d u c t , w h i c h c o n t a i n e d t h r e e n e w p h o t o -
c h r o m i c c o mp o u n d s . A ft e r e x t e n s iv e c o lu m n c h r o m a t o g r a p h y o n l y
1
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c o mp o u n d [ 1 1 ] w a s r e m a r k a bl y s i m i l ar t o t h e c a r b e n o id p r e c u r s o r ,
b u t d i s p l a y e d a n a d d it i o n al A B s y s t e m w i t h a d o u b l e t a t d 3 . 39 a n d
a t d 4 . 6 6 (J ¼ 8 . 2 H z ). A r o u t i n e D O e x p e r i m e n t r e v e a l e d t h a t t h e
2
d o u b l e t a t d 4 . 6 6 w a s d u e t o a h y d r o x y l g r o u p a n d t h u s s u g g e s t e d
t h e s tr u c t u re a s 1 8 , n ¼ 2 , w h i c h w a s s u b s e q u e n t l y c o n f i r m e d b y
1
H R MS . T h e H N M R d a t a f o r 1 8, n ¼ 2 c o m p a r e s f a v o u r a b l y w i t h t h a t
f or o t h e r 2 - h y d r o x y m a lo n a t e e s t e r s w h e r e t h e m e t h i n e p r o t o n t y p i -
c a l l y r e so n a t es a t c a . d 3 . 9 a n d t h e h y d r o x y l p r o t o n a t d c a . 4 . 7 [ 1 2 ] .
T h e i n t e r c e p t i o n o f r h o d iu m c a r b e n o i d s b y w a t e r h a s b e e n p r e v i o u s l y
n o t e d [ 1 2 , 1 3 ] . A s i m i l a r r e s u l t w a s o b t a in e d w h e n d i a z o c o m p o u n d 1 6 ,
n ¼ 3 w a s t re a t e d w i th R h ( O Ac ) i n C H C l . U n f o r t u n a t e l y , i t w o u l d
2
4
2
2
a p p e a r t h a t t h e c a r b e n o i ds g e n e r a t e d f r o m 1 6 f a i l t o u n d e r g o a n i n t r a -
m o l e c u l a r c yc l i s a t io n c o m p a r a bl e t o t h a t o b s e r v e d f o r 9 a n d a r e
i n s t e a d i n t e r c e p t e d b y w a te r , d e s p it e t h e r e a c t i o n b e i n g r u n u n d e r
a n h y d r o u s c on d i t i o n s , t o a ff o r d 1 8 i n m o d e r a t e y i e l d .
CONCLUSIONS
T w o n o v e l 3 - ( h y dr o x y a lk y l) - 1 -n ap h t h o l s h a v e b e e n o b t a i n e d b y a t w o
s t e p s tr a t e g y f r o m a n i s o q u i n o l i n i u m s a l t e m p l o y i n g a B r a d s h e r
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Naphthopyrans Containing a Latent Carbene Unit
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2 H- n a p h t h o [ 1 , 2 - b] p yr an s b y a n a c i d c a t a ly s e d r e a c t i o n w i t h a p r o p - 2 -
y n - 1 - o l . D i a z o a c yl a t io n o f t h e p e n d an t h y d r o x y l f u n c t io n s a n d s u b -
s e q u e n t r h o d iu m c a r b e n o i d g e n e r a t i o n f a i l e d t o a f f o r d t e t r a c y c l i c
c y c l o a d d u c t s a n d i n s t e ad t h e c a r b e n o i d w a s i n t e r c e p t e d b y w a t e r . T h i s
c o n t ra st s w i t h o u r p r e vi o u s o b s e r v a t i o n s a n d i n d i c a t e s t h a t t h e l e n g t h
o f t h e t e t h e r d i c t at e s t h e m o d e o f t h e c a r b e n o i d a d d i t i o n p r o c e s s .
F u r t h e r w o r k i n t h i s a r e a i s o n g o i n g.
REFERENCES
[
1
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K
u
t
h
a
n
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(
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9
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3
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v
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H
e
t
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l
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m
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[
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B
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u
a
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L
a
u
r
e
n
t
,
H
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&
D
u
¨
r
r
,
H
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(
2
0
0
1
)
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P
u
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´
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[ 6 ] U s h a k o v , E . N . , N a z a r o v , V . B . , F e do r ov a , O . A . , G r o m o v, S . P . , C h e b u n ’ k ov a , A . V . ,
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( 2 0 0 4 ) . Tetrahedron Lett. , 45, 6 1 5 1 .
[
8
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C lO , M ¼ 6 0 3 . 0 4 , t r i c l i n i c, s p a c e g r ou p P– 1 ,
3 4 3 1
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a ¼ 1 1 . 0 2 1 1 ( 9) , b ¼ 1 1 . 4 9 7 0( 9) , c ¼ 1 2 . 5 3 3 0 (1 0) A , a ¼ 8 5 . 1 0 2 ( 4) , b ¼ 8 5 . 0 9 7 ( 4 ),
ꢁ
c ¼ 6 9 . 7 9 1 ( 2 ) , U ¼ 1 4 8 2 . 2 (2 ) A , Dc a l c d ¼ 1 . 3 5 1 M g m ꢂ3, Z ¼ 2 , M o Ka r a d i a t i on
3
˚
ꢂ1
˚
( k ¼ 0 . 7 1 0 7 3 A ) , l ¼ 0 . 1 8 2 m m , T ¼ 1 2 0 (2 ) K , 8 2 2 5 m e a su r e d r e fl ec t i o ns , 3 9 4 3
o b s e r v e d r e f l e ct io ns ( Rint ¼ 0 . 1 0 6 0 ), R1 ¼ 0 . 1 9 2 0 [ F2 > 2 r( F2) ] , wR2 ¼ 0 . 2 3 3 7 ( a l l
d a t a ) . T h e s t ru c t u r e w a s s o lv ed a n d r ef in e d u s i n g t h e S HE L X L- 9 7 s u i t e o f
p r o g r a ms [ 1 4 ] . C ry s t a ll o g r ap hi c d a t a f or t h is s t r u c t u r e h a v e b e e n d e po s i t ed w i t h
t h e C a m b r i d ge C ry s t a ll o g r ap hi c D a t a C en t re , n o. C C DC 2 4 6 5 6 7 .
[ 9 ] M an n a , S . & F a lc k, J . R . ( 19 9 0 ) . J. Org. Chem. , 47, 5 0 2 1 ; G u pt a , R . B . & F ra n c k ,
R . W . ( 1 9 9 0 ) . Synlett, 3 5 5 .
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[ 1 3 ] A l l e r , E . , B r o w n , D . S . , C ox , G . G . , M i ll er , D . J . , & M oo d y , C . J . ( 1 9 9 5 ). J. Org.
Chem. , 60, 4 4 4 9 .
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[ 1 4 ] S h e l d r i c k , G . M . ( 19 9 7 ) . SHELXL-97 Program System, U n i v e rs i t y o f G o t t i n g e n:
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