Photochromic naphtho [2,1-b]pyran compounds containing bithienyl or terthienyl substituents, process for their manufacture, and photochromic materials and articles obtained

A process for preparing a photochromic compound having a formula:

• in which the Th2 group represents a bithienyl group in one of the positions 5 to 10 of the naphthenic ring system and corresponds to the formula:
• in which:
• R denotes a substitutent in one of the positions 3, 3′, 4, 4′ or 5′, chosen from a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a group OR3, SR3, COR3 and COOR3, in which R3 denotes a hydrogen atom, an alkyl group, an aryl group, an amino group, an NO2, CN or SCN group, a halogen atom or a mono- or polyhaloalkyl group;
• R1 denotes a Th2 group as defined above or a Th3 group of formula:
• in which
• R is a substituent as denoted above which can occupy one of the positions 3, 3′, 3″, 4, 4′, 4″, and 5″;
• and
• R2 denotes a Th2 group, a Th3 group, an aryl group, a naththyl group, a thienyl group, a furyl group, a pyrrolyl group or an N-alkylpyrrolyl group, the process comprising reacting, in the presence of an acid catalyst, a propargyl alcohol of formula:
• in which R1 denotes a Th2 group as defined above or a Th3 group as defined above;
• with a 2-naphthol of formula:
• in which Th2 is as defined above.