Method for preparing indolenaphthopyrans

A process for producing an indolenaphthol compound comprising:

• (1) providing a phenylnaphthol compound comprising the core skeletal structure represented by Formula (I):
• wherein,
• m is 0 to 4, and n is 0 to 4;
• R1 independently for each m, and R2 independently for each n, are each independently selected from:
• i. a halo group selected from fluoro, chloro, bromo, or iodo;
• ii. substituted or unsubstituted alkyl;
• iii. substituted or unsubstituted heteroaryl;
• iv. substituted or unsubstituted alkoxy or substituted or unsubstituted aryloxy;
• v. substituted or unsubstituted alkylthio or substituted or unsubstituted arylthio;
• or
• two R1 groups or two R2 groups on adjacent carbon atoms may connect to form a ring;
• R3 is selected from substituted or unsubstituted 2-pyridyl or substituted or unsubstituted 2-quinolyl,
• wherein the pyridyl or quinolyl substituents are selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryloxy, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, halogen, amino, ester, carboxylate, or hydroxyl;
• and
• R4 is selected from hydrogen, substituted or unsubstituted alkyl, alkoxymethyl, substituted or unsubstituted silyl, or acyl;
• and
• (2) cyclizing the phenylnaphthol compound of Formula (I) in the presence of a transition metal catalyst to produce an indolenaphthol compound having the core skeletal structure represented by Formula (II):
• wherein m, n, R1, R2, and R4 are as defined above by Formula (I).