A practical and efficient process for the preparation of tazarotene

We describe an efficient process for the preparation of tazarotene starting from 4,4-dimethyl-6-bromothiochromane S-oxide (9), 2-methyl-3-butyn-2-ol (10), and 6-chloronicotinic acid ethyl ester (8). Our synthetic pathway compares favorably over the previously reported procedures since tazarotene was prepared straightforwardly using cheap reagents and without the employment of hazardous organometallic compounds. The process is based on the use of sulfoxide 9 as key starting material. The C-15 framework of the target was built up by means of two different approaches based on a palladium-mediated coupling reaction. The molecular structure of compound has been confirmed by X-ray crystallography.