New route for synthesis of furan derivatives from protected α-ketols and ketones. A total synthesis of furoventalene
Abstract
Reaction of acetonyl tetrahydropyranyl ether (1) with ketones (2a–d) in the presence of lithium di-isopropylamide and zinc chloride produces the cross-aldol condensation products (3a–d), which are transformed into 3-methylfurans (4a–d), by treatment with aqueous toluene-p-sulphonic acid. Similarly, tetrahydrobenzofurans (7a–d) are obtained by using 2-hydroxycyclohexanone trimethylsilyl ether (5). The application of this methodology enabled us to complete a total synthesis of furoventalene (11).