Thianthrene bromination

Bromoacetylthianthrene, which can be produced by direct acylation as well as via bromination of 2-acetylthianthrene (63MI2) (for comparable dibromination of 2,7-diacetylthianthrene, see 64MI1), has been used in its capacity as an a-bromo-ketone to produce thianthren-2-yl-substituted heterocycles such as 55, 56, 57 (63MI2 73BSF1460), and 2-amino-4-(thianthren-2-yl)thiazole (63MI2), by condensation with 2-aminopyridine,... 

The thianthrene ring system survives standard phenolic 0-demeth-ylation procedures, thus, 2,7-dimethoxythianthrene (HBr) (15 LA194) and 2,3,7,8-tetramethoxythianthrene (HI) (29LA162) were converted to the bis- and tetrakis-phenols. It was shown that the 2,7-dihydroxythianthrene is brominated at each of the positions ortho to the hydroxyl groups (15LA194). 

Dicyanodibenzodioxin as well as tetracyano derivatives of thianthrene and phenoxathiin have been synthesized by aromatic nucleophilic substitution reaction of the bromine atom and nitro group in 4-bromo-5-nitrophthalonitrile <2001H(55)1161>. 

Derivatized thianthrene molecules (3) are prepared by functionalizing preformed thianthrene or starting with the functionality present followed by heterocycle formation (Figure 4). The former involves electrophilic substitution of the thianthrene nucleus (1) followed by reaction to give the desired substituents. The most common electrophilic reactions are bromination and Friedel-Crafts acylation which have shown good selectivity in giving thianthrenes substituted primarily in the 2,7-positions with minor amounts of the 2,8-isomers. 

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