Substituted spiro 2H-1-benzopyran-2,3'-(3H)-naphtho(2,1-b)pyrans particularly suitable for use as precursors to stable colored pyrylium salts are disclosed.

This invention relates to substituted spiropyrans. 
More specifically, this invention relates to 
spiro(2H-1-benzopyran-2,3'-(3H)-naphtho(2,1-b)pyrans). 
Spiropyrans are of interest as precursors for the UV generation of colored 
pyrylium salts for use in applications as varied as dosimetry and optical 
data storage to the formation of non-contact decorative patterns (See S. 
Maslowski, "High Density Data Storage UV Sensitive Tape," Applied Optics, 
13, No. 4, 857 (1974). 
The present invention provides a novel type of substituted spiropyrans 
particularly suitable for use as precursors to stable colored pyrylium 
salts. 
According to this invention there is provided a compound having the formula 
##STR1## 
wherein R represents C.sub.1 -C.sub.12 alkyl, alkylene aryl, aryl, 
unsaturated aryl, or cycloalkyl and R' represents dialkylamino. 
The term "C.sub.1 -C.sub.12 alkyl" is used in the specification and claims 
to signify a straight or branched alkyl group containing from 1 to 12 
carbon atoms, with no more than 6 carbon atoms in its longest chain. 
The term "aryl" is used in the specification and claims to signify phenyl 
or naphthyl, both of which may be unsubstituted or substituted in up to 
two positions with a substituent selected independently from C.sub.1 
-C.sub.4 alkyl, halo or --NO.sub.2. "C.sub.1 -C.sub.4 alkyl" is used above 
to signify a straight or branched alkyl group containing from 1 to 4 
carbon atoms and "halo" is used above to signify fluoro, chloro, iodo and 
bromo. 
The term "alkylene aryl" is used in the specification and claims to signify 
a moiety of the formula M--X--, wherein M represents aryl, as defined 
above, and X represents a straight or branched alkyl group having from 1 
to 3 carbon atoms. 
The term "unsaturated alkyl group" is used in the specification and claims 
to signify a straight or branched alkyl group containing at least 1 
carbon-carbon double bond and having from 2 to 12 carbon atoms, with no 
more than 6 carbon atoms in its longest chain. 
The term "cycloalkyl" is used in the specification and claims to signify 
saturated alkyl group having from 3 to 6 carbon atoms. 
In the term "dialkylamino," as used herein, each alkyl substituent is 
independently selected from a straight or branched alkyl group containing 
from 1 to 4 carbon atoms. 
The novel substituted spiropyrans of this invention are prepared by the 
acid-catalysed condensation of 4-dialkylamino salicylaldehyde with the 
appropriately substituted methyl ketone to form a substituted styryl 
ketone intermediate which is not isolated. 2-Hydroxynaphthaldehyde is then 
added to the reaction mixture to thereby produce the desired substituted 
spiropyrans. Substantially equimolar amounts of the substituted methyl 
ketone, the 4-dialkylamino salicylaldehyde and the 1-hydroxynaphthaldehyde 
are utilized in the process, which proceeds according to the following 
reaction formula: 
##STR2## 
wherein R and R' are as defined above. 
The substituted methyl ketones utilized herein are available commercially 
or can be prepared by using the procedures as set forth in Organic 
Functional Group Preparation, S. R. Sandler and W. Karo, Academic Press, 
New York, p. 169 and Synthetic Organic Chemistry, R. B. Wagner and H. D. 
Zook, New York, Wiley and Sons, Inc., p. 339. 
The spiropyrans of this invention will react with photogenerated protic 
acids to form colored pyrilium salts. In this well-known method the protic 
acids, which are typically hydrogen halides, are generated by light within 
a substrate containing the spiropyran. Precursors for the hydrogen halides 
are typically tri halo alcohols, i.e., 2,2,2-tribromoethanol, which absorb 
light and generate hydrogen halides which react with the spiropyran to 
give a colored salt. 
The stability of the colored pyrylium salts resulting from interaction of 
photogenerated protic acids with the spiropyrans is important. It is known 
that the nature of ring substitution (see rings A and B, equation 2 below) 
can influence stability . (G. Arnold, G. Paal, and H. P. Vollmer, Z. 
Naturforsch, B 25 (12), 1413 (1970); U.S. Pat. No. 3,733,197 to C. 
Schiele.) 
Further, it has now been found that the substitution at the 7-position of 
ring B below of an .pi. electron-donating group (e.g. dialkylamino) is 
effective in stabilizing the color of pyrylium salts. The compounds of 
this invention have been found to be particularly effective in this 
respect. 
##STR3## 
It has also been discovered that the spiropyrans of this invention in which 
R is an unsaturated alkyl group, may be copolymerized with acrylates via a 
free radical process which utilizes well known initiators such as, for 
example, azobis (isobutyronitrile) and 2,2'-azobis(2-methylpropionitrile). 
The resulting copolymers are precursors to chromogenic materials that find 
varied application from optical data storage to the formation of 
noncontact decorative patterns. 
The term "acrylates" as used herein refers to acrylates and methacrylates 
that have the formula: 
##STR4## 
wherein X is H or CH.sub.3 and X' is H or a straight or branched alkyl 
group having from 1 to 12 carbon atoms.

Reference is now made to the following example which is provided to 
illustrate but not to limit the practice of this invention. 
EXAMPLE 
Preparation of 
3-methyl-7-dimethylamino-2,2'-spiro(2H-1-benzopyran-2,3'-(3H)-naphtho(2,1- 
b)pyran) 
To a solution of 4-dimethylamino salicylaldehyde (5.45 g, 0.033 mol) and 
methyl ethyl ketone (2.4 g, 0.033 mol) in 12 ml of glacial acetic acid 
cooled in ice water there was added anhydrous hydrogen chloride. The 
addition of hydrogen chloride was made below the liquid surface for a 
period of 75 min. To the resulting magenta colored reaction mixture there 
was added a solution of 2-hydroxynaphthaldehyde (5.68 g, 0.033 mol) in 15 
ml of glacial acetic acid. The addition of hydrogen chloride was resumed 
as before, while the reaction mixture was cooled at ice water bath 
temperature. After ca. 150 min, the passage of hydrogen chloride was 
terminated and the reaction was stopped and set aside. 
After ca. 16 hrs. the intensely colored (deep magenta) reaction mixture 
formed a gelatinous mass. The latter was slurried with 200 ml of ether, 
and the resulting two-phase mixture was separated by decanting the liquid 
ether phase. Ether (200 ml) was added to the highly colored ether 
insoluble semi-solid and after slurrying, again gave two phases. The 
ethereal layer was decanted, and the ether insoluble residue dried in 
vacue. The resulting bluish-green gummy solid was slurried with 200 ml of 
acetone and dilute ammonium hydroxide was added until the mixture was 
weakly alkaline. 
The resulting dark amber reaction mixture was filtered, and the filtrate 
(two-phases) was concentrated on a Rota-vap. The dark residue was treated 
with ether, and the dark amber ethereal phase separated and dried over 
anhydrous magnesium sulfate. The dried ethereal solution was concentrated 
to dryness under reduced pressure and left an iridescent green solid 
residue (7.1 gm). Recrystallization of this crude reaction product from 
benzene-hexane and subsequently from hexane alone gave the desired 
product. The product sintered and shrank at 130.degree.-40.degree. and 
carbonized at 152.degree.-6.degree.. Anal. Calcd. for C.sub.24 H.sub.21 
NO.sub.2 : C, 81.1; H, 6.0; N, 3.9. Found: C, 80.6; H, 6.1; N, 3.6. UV 
(THF) 308 nm (24,470). 
The NMR assignments of the desired product summarized below. 
______________________________________ 
##STR5## 
Proton H.sub.A H.sup.B H.sub.C 
H.sub.D & H.sub.E 
______________________________________ 
Chemical* 2.79(s) 1.97(s) 6.05(d) 
in aromatic 
shifts, ppm, 
Aryl protons 
6.1-8.2 
______________________________________ 
*In CDCl.sub.3 solvent, TMS as internal standard.