Synthesis of Oligomeric 4 <i>H</i> ‐1,2,6‐Thiadiazines

Abstract The synthesis of oligomeric amino‐4 H ‐1,2,6‐thiadiazines, with terminal phenyl groups, containing up to four thiadiazine units is reported. The synthesis started from 3,5‐dichloro‐4 H ‐1,2,6‐thiadiazin‐4‐one and a key intermediate was 5,5′‐azanediylbis(3‐chloro‐4 H ‐1,2,6‐thiadiazin‐4‐one) which was coupled with phenyltributyl‐stannane in a Stille coupling to provide a bisthiadiazine oligomer. A stepwise C─N coupling reaction of 3,5‐dichloro‐4 H ‐1,2,6‐thiadiazin‐4‐one with 3‐amino‐5‐phenyl‐4 H ‐1,2,6‐thiadiazin‐4‐one provided a trithiadiazine oligomer, while similar reaction of 5,5′‐azanediylbis(3‐chloro‐4 H ‐1,2,6‐thiadiazin‐4‐one) with an excess of 3‐amino‐5‐phenyl‐4 H ‐1,2,6‐thiadiazin‐4‐one yielded a tetrathiadiazine oligomer. Two amino‐substituted bisthiadiazine oligomers with terminal anilino or alkylamino groups were also prepared. The anilino derivative was accessed by a C─N coupling of 5,5′‐azanediylbis(3‐chloro‐4 H ‐1,2,6‐thiadiazin‐4‐one) with aniline, while reaction with 2‐ethylhexane‐1‐amine occurred under thermal conditions in the absence of Pd to give a bisthiadiazine with terminal alkylamino groups. The optical and electronic properties of all oligomers were also studied by UV‐vis spectroscopy, cyclic voltammetry and DFT computations.