Method of preparing sultines

1. A method of preparing a sultine of formula (V) from a dihalogeno compound of formula (IV)

said method comprising the step of:

reacting said dihalogeno compound (IV) with a hydroxymethanesulfinate salt in a DMSO solvent so as to prepare said sultine (V),

wherein:

R 1 , R 2 , R 3 and R 4 are each independently selected from the group consisting of: hydrogen, hydroxyl, C 1-20 alkyl, C 1-20 alkoxy, amino, C 1-20 alkylamino, di(C 1-20 alkyl)amino, halogen, cyano, thiol, C 1-20 alkylthio, nitro, C 1-20 alkylcarboxy, C 1-20 alkylcarbonyl, C 1-20 alkoxycarbonyl, C 1-20 alkylcarbonyloxy, C 1-20 alkylcarbonylamino, C 5-20 aryl, C 5-20 arylalkyl, C 5-20 aryloxy, C 5-20 arylalkoxy, C 5-20 heteroaryl, C 5-20 heteroaryloxy, C 5-20 heteroarylalkoxy and C 5-20 heteroarylalkyl; and

X is selected from the group consisting of: Cl, Br and I.

2. The method of claim 1 , wherein X is Cl or Br, and NaI is present.

3. The method of claim 1 , wherein a metal carbonate base is present.

4. The method of claim 1 , wherein said hydroxymethanesulfinate salt is sodium hydroxymethanesulfinate.

5. The method of claim 1 , wherein R 1 , R 2 , R 3 and R 4 are all hydrogen.

6. The method of claim 1 , wherein said preparation is performed on a scale of at least 0.3 moles of the dihalogeno compound (IV).

7. The method of claim 1 , wherein said temperature is in the range of 50 to 100° C.

8. The method of claim 1 , further comprising the step of:

reacting said sultine (V) with maleic anhydride at elevated temperature to generate a naphthalic anhydride as a Diels-Alder adduct.

9. The method of claim 8 , wherein said naphthalic anhydride is used as a precursor for naphthalocyanine synthesis.

10. The method of claim 9 , wherein said naphthalocyanine synthesis proceeds via conversion of said naphthalic anhydride to a benzisoindolenine.

11. The method of claim 9 , wherein R 1 , R 2 , R 3 and R 4 are each hydrogen.