One-pot synthesis of benzisoindolenines used in the preparation of naphthalocyanines

A method of effecting a one-pot conversion of a tetrahydronaphthalic anhydride of formula (I):

• to a nitrate salt of a benzisoindolenine of formula (II):
• said method comprising heating said tetrahydronaphthalic anhydride of formula (I) with a reagent mixture comprising ammonium nitrate so as to effecting concomitant dehydrogenation during the conversion, wherein:
• R1, R2, R3 and R4 are each independently selected from the group consisting of:
• hydrogen, hydroxyl, C1-20 alkyl, C1-20 alkoxy, amino, C1-20alkylamino, di(C1-20alkyl)amino, halogen, cyano, thiol, C1-20 alkylthio, nitro, C1-20 alkylcarboxy, C1-20 alkylcarbonyl, C1-20 alkoxycarbonyl, C1-20 alkylcarbonyloxy, C1-20alkylcarbonylamino, C5-20 aryl, C5-20 arylalkyl, C5-20 aryloxy, C5-20 arylalkoxy, C5-20heteroaryl, C5-20heteroaryloxy, C5-20heteroarylalkoxy and C5-20 heteroarylalkyl.