Synthesis of chromanes by sequential ‘[3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes

Functionalized chromanes were prepared by sequential ‘3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 1,1,3,3-tetramethoxypropane, 3-silyloxyalk-2-en-1-ones, and 1,1-diacetylcyclopropane. The first step of the sequence involves 3+3] cyclizations of the starting materials to give 2-(3-chloropropyl)phenols. The subsequent cyclization proceeds by intramolecular nucleophilic substitution. 6-(2-Hydroxybenzoyl)chromanes were prepared based on sequential ‘3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 3-formylchromones.