The lithiation of 4-heterosubstituted dibenzothiins 1 (phenoxathiin, phenothiazine and thianthrene) with lithium and a catalytic amount of 4, 4′-di-tert-butylbiphenyl (DTBB, 7.5% molar) in THF at temperatures ranging from− 90 to− 78° C gives the corresponding functionalised organolithium intermediate I, which by reaction with different electrophiles [H2O, D2O, ButCHO, PhCHO, Ph (CH2) 2CHO, Me2CO, Et2CO,(CH2) 5CO,(CH2) 7CO] at ...