One-Pot Synthesis of Spiropyrans

A highly efficient one-pot synthetic strategy for the preparation of spiropyrans was developed. The method is free of special equipment and operations, and meanwhile, it is energy- and time-saving compared to the reported three-step procedures. Tolerated with various solvents, bases, aldehydes, and alkyl bromides, the commonly used "T-type" spiropyrans (SP1 s) were synthesized in one-pot with highly improved yields. To avoid the hydrolysis of the spiropyran moiety during the synthesis of the linear type spiropyrans (SP2 s), a strategy of the combination of pre-alkylation of phenolic hydroxyl group of 5-hydroxy-indole and a one-pot synthesis of the spiropyran moiety was also designed. With a short reaction time, simplified workups, and reduced chemical waste, this one-pot synthetic strategy for the synthesis of spiropyran compounds would facilitate related research in the fields of biology and materials science, and would be attractive to the industrial application.