Efficient Synthesis of a 2-Decyl-tetradecyl Substituted 7-Bromophenothiazine-3-carbaldehyde Building Block for Functional Dyes

(1) Polyfunctional molecules are versatile building blocks for efficient syntheses of novel phenothiazine-based materials with promising electronic properties. A prerequisite is a facile, high yielding access to these building blocks that bear solubilizing moieties and functional groups for orthogonal transformation. (2) Here, an efficient, improved two-step protocol for accessing a solubilizing 2-decyl-tetradecyl functionalized phenothiazine, i.e., an N-alkylated 7-bromophenothiazine-3-carbaldehyde, by Vilsmeier–Haack formylation and NBS (N-bromo succinimide) bromination is reported. (3) The sequence proceeds with higher yields and in shorter reaction times than the standard access employing bromination with elementary bromine. In addition, the work-up procedure essentially uses absorptive filtration on a plug of silica with the eluent.