Synthesis of bis[1,2]dithiolo[1,4]thiazine imines from Hünig’s base

N-Ethyldiisopropylamine, S2Cl2 and DABCO in chloroform at room temperature form intermediate salts which react with nucleophiles to give tricyclic bis[1,2]dithiolo[1,4]thiazine derivatives. The reactions of some representative amino compounds as the nucleophiles are now described. With arenesulfonamides 1a,b and their N,N-dichloro derivatives 2a,b, the N,N′-bis(arylsulfonyl)dithiolothiazinediimines 3a,b are formed in modest yields. With toluene-p-sulfonohydrazide and aniline the more complex reactions give only the monohydrazone 7 and the bicyclic anilino derivative 8, respectively, in very low yields. The diimines 3a,b are also produced, in better yield, from the bis(1,2-dithiole-3-thione) 4 with chloramine B and T; similarly the analogous monothione 12 gives the monoimines 13a,b. The reaction rates and yields (up to 93%) in the conversion of 12 to 13 are greatly increased by scandium triflate. Possible reaction mechanisms are considered.