Photochromic naphtho [2,1-b]pyran compounds...

Details Photochromic naphtho [2,1-b]pyran compounds... Photochromic naphtho [2,1-b]pyran compounds...

1999-07-08

2001-11-06

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Composite

C052S204500, C296S084100, C296S146100, C501S013000, C548S525000, C548S527000, C549S059000

Reexamination Certificate

active

06312811

ABSTRACT:

The invention relates to photochromic compounds, more particularly heterocyclic compounds of the naphtho[2,1-b]pyran family substituted with bi- or terthienyl groups, and to their application in the field of materials and articles with variable optical transmission.
When photochromic compounds are subjected to irradiation containing ultraviolet rays (sunlight, xenon lamps or mercury lamps), they undergo a reversible color change. As soon as the excitation stops, they regain their original color.
In recent years, organic materials intended for optical applications have been the subject of considerable research. Ophthalmic glasses, glass for the construction industry, motor vehicle or airplane windshields and helmet visors, whose transparency in the visible range can be modified by using photochromic compounds, have particularly attracted attention. For this type of application using sunlight (heliochromism), the photochromic active compound must satisfy a certain number of criteria, among which are:
high colorability in the visible range after excitation with light (colorability is a measure of the capacity of a photochromic compound to exhibit an intense color);
an absence of coloration (or a weak coloration) in the initial state;
rapid kinetics of thermal decolorization at room temperature;
low decolorization with visible light; and
a high speed of coloration.
One of the major difficulties encountered with photochromic compounds is that of obtaining a compromise between high colorability and rapid decolorization kinetics. The reason for this is that, under continuous solar irradiation, a photostationary equilibrium is established between the molecules which become colored under the action of ultraviolet light and those which become decolorized under the conjugate action of temperature and visible light. Thus, frequently, an increase in the rate of decolorization entails a decrease in the colorability.
The Applicant Company has discovered a novel family of naphtho[2,1-b]pyrans substituted with bithienyl or terthienyl groups, which have particularly advantageous photochromic properties.
The compounds in accordance with the invention have, compared with the naphtho[2,1-b]pyrans of the prior art, a colorability which is at least equivalent but higher coloration speeds and decolorization speeds. The following have also been found for these compounds:
an absence of coloration or only very weak coloration in the original state;
a particularly long life;
a sensitivity to low-energy ultraviolet rays (wavelengths greater than 380 nm);
an absorption of the colored forms at long wavelength (539 nm).
This combination of characteristics makes these novel compounds particularly advantageous for the manufacture of photochromic materials, in particular comprising a substrate made of transparent polymer material such as organic glasses with variable optical transmission (glass for sunglasses, glass for the construction industry, motor vehicle or airplane windshields, and riding or flying helmet visors).
The photochromic compounds can be incorporated directly into the organic glass substrate or dissolved in a polymer film stuck to the organic glass substrate.
The compounds which form the subject of the invention are [3H]naphtho[2,1-b]pyrans (I) comprising, on one of the positions 5 to 10, preferably position 8, of the naphthalene ring system, a bithienyl (Th
2
) group and comprising in position 3 at least one (Th
2
) group or at least one terthienyl (Th
3
) group.
More particularly, the compounds of the invention correspond to the general formula below:
in which Th
2
is represented by formula (II):
in which:
R denotes a substituent which can occupy one of the positions 3, 3′, 4, 4′ or 5′, preferably position 5′, and which is chosen from a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a group OR
3
, SR
3
, COR
3
or COOR
3
in which R
3
denotes a hydrogen atom, an alkyl or cycloalkyl group, an aryl group, an amino group, an NO
2
, CN or SCN group, a halogen atom or a mono- or polyhaloalkyl group,
R
1
denotes a Th
2
group as represented by formula (II) or a terthienyl (Th
3
) group as represented by formula (III):
in which R is a substituent as denoted above in describing formula (II) and which can occupy one of the positions 3, 3′, 3″, 4, 4′, 4″, and 5″, preferably position 5″, and
R
2
can be a Th
2
group as defined in formula (II), a Th
3
group as defined in formula (III), an aryl group, a naphthyl group, a thienyl group, a furyl group or a pyrrolyl or N-alkylpyrrolyl group.
In this definition of R
2
, an aryl group denotes a phenyl, a phenyl which is mono- or polysubstituted with one (or more) alkyl, cycloalkyl, phenyl or amino substituents(s), a halogen, a group OR
3
, SR
3
, COR
3
or COOR
3
(in which R
3
has the same meaning as above); the groups R
2
of the naphthyl type can be substituted with the same substituents.
The heterocyclic groups (thiophene, furan, pyrrole) can be benzo-fused and the benzo group can bear alkyl, cycloalkyl, aryl, OR
3
, SR
3
, COR
3
or COOR
3
(in which R
3
has the same meaning as above), amino, NO
2
, CN or SCN, or mono- (or poly-)haloalkyl substituents.
Preferably, R
1
represents a Th
3
group.
In the bithienyl and terthienyl substituents, the alkyl groups are preferably C
1
-C
6
alkyl groups, for example methyl, ethyl, propyl, butyl, pentyl and hexyl; the cycloalkyl groups are C
5
-C
7
cycloalkyl groups, for example cyclopentyl, cyclohexyl and cycloheptyl; the aryl groups denote a phenyl, a phenyl which is mono- or polysubstituted with one (or more) C
1
-C
6
alkyl, C
5
-C
7
cycloalkyl, phenyl and amino substituent(s); the halogens preferably represent Br, Cl and F; and the mono- (or poly-)haloalkyl groups are preferably mono-(or poly-)chloro or -fluoro C
1
-C
6
alkyl groups, for example CF
3
.
The compounds represented by formula (I) can be prepared by the coupling reaction of a suitably substituted propargyl alcohol (A) with a 2-naphthol bearing the bithienyl group (B) (Scheme 1).
This reaction is carried out in dichloromethane in the presence of an acid catalyst (PPTS: pyridinium para-tolueuesulfonate):
in which R
1
, R
2
and Th
2
have the above meaning.
Scheme 1
The propargyl alcohols can be prepared as described in Scheme 2, by the action of lithium acetylide on a suitably substituted ketone.
Scheme 2
The naphthols (B) can be prepared in two different ways depending on whether the bithienyl group must occupy position 7 or the other positions (5, 6, 8-10) on the target molecule (I).
The preparation of 5-(2,2′-bithien-5-yl)-2-hydroxynaphthalene 6 (precursor of the naphthopyrans (I) substituted in position 7 with the Th
2
group) is carried out in four steps as indicated in Scheme 3. Bithienylmagnesium bromide 2 (obtained by a transmetallation reaction using 2,2′-bithiophene 1) reacts with 6-methoxy-1-tetralone (3) to give the derivative (4). After an oxidation reaction in the presence of chloranil (2, 3, 5, 6-tetrachloro-1,4-benzoquinone), the resulting compound 5 is demethylated with boron tribromide in dichloromethane to give the expected naphthol 6.
Scheme 3
The naphthols of the type 9 (which give access to the naphthopyrans of formula (I) substituted in positions 5, 6, 8, 9 or 10 with a Th
2
group) are prepared by a coupling reaction, catalyzed with a palladium catalyst such as Pd (PPh
3
)
4
, between the bithiophene boron derivative 7 and a bromo-2-naphthol (Scheme 4) or a 2-naphthol substituted with a triflate group, the bromine substituent or triflate group occupying one of positions 3, 4 or 6-8 of the naphthalene ring system.
Scheme 4
The naphthopyrans of the present invention show particularly advantageous photochromic properties when compared with those of molecules of the same family of the prior art. A toluene solution of the compounds of formula (I) becomes colored and decolorizes very rapidly at room temperature. The main advantage of these novel compounds is that the rapid res

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