Process for the preparation of 4-phenyldibenzothiophene
The invention relates to a novel method for the preparation of 4-phenyldibenzo[b,d]thiophene which can be conducted in one pot up to the thiophene ring formation. The synthesis is based upon dihalobenzenes and phenyllithium, which are readily obtainable, and can give higher yields (based upon either reactant) than the yields current methods, which use a synthetic pathway based upon dibenzo[b,d]thiophene.
1. A method for the preparation of a 4-phenyldibenzo[b,d]thiophene, the method comprising the following steps:
a) reacting a dihalobenzene with a phenyllithium to give a terphenyllithium:
b) reacting the terphenyllithium with sulfur to give a thiollithium:
c) treating the thiollithium with an acid to form a thiol; and
d) reacting the thiol with an oxidizer to form the 4-phenyldibenzo[b,d]thiophene:
wherein R, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from the group consisting of hydrogen, phenyl, an alkyl substituent (—C n ) and an ether substituent (—C m1 —O—C m2 ), where n, m1 and m2 are each an integer, with each of n and (m1 +m2+1) being in the range of 0 to 16; and wherein X 1 and X 2 are each independently selected from the group consisting of chlorine, iodine and bromine.
2. A method as in claim 1 , wherein each of n and (m1+m2+1) is in the range of 0 to 6.
3. A method as in claim 1 wherein X 1 and X 2 are each chlorine; X 1 is chlorine and X 2 is iodine; X 1 is chlorine and X 2 is bromine; or X 1 and X 2 are each bromine.
4. A method as in claim 3 wherein R, R 1 or R 2 are each, independently, an alkyl group.
5. A method as in claim 4 wherein each of R, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is hydrogen.
6. A method as in claim 1 wherein the oxidizer in step d) comprises sulfur.
7. A method as in claim 2 wherein the oxidizer in step d) comprises sulfur.
8. A method as claim 3 wherein the oxidizer in step d) comprises sulfur.
9. A method as claim 4 wherein the oxidizer in step d) comprises sulfur.
10. A method as in claim 5 wherein the oxidizer in step d) comprises sulfur.