title: The silylalkyne-Prins cyclization: stereoselective synthesis of tetra- and pentasubstituted halodihydropyrans.
abstract: [reaction: see text] A new type of Prins cyclization using silylated secondary homopropargylic alcohols and aldehydes yielding tetra- and pentasubstituted dihydropyrans is described. The presence of the trimethylsilyl group in the triple bond favors the Prins cyclization and minimizes the 2-oxonia-[3,3]-sigmatropic rearrangement as a competitive alternative pathway. Ab initio theoretical calculations of the species involved in the rearrangements support the proposed mechanism. The process is highly stereoselective, affording cis-dihydropyran as the only isomer.
authors.affiliation: Instituto Universitario de Bio-Organica "Antonio Gonzalez", Universidad de La Laguna, C/Astrofísico Francisco Sanchez 2, 38206 La Laguna, Tenerife, Spain.
authors.forename: Pedro O
authors.initials: PO
authors.lastname: Miranda
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ramírez
authors.forename: Víctor S
authors.initials: VS
authors.lastname: Martín
authors.forename: Juan I
authors.initials: JI
authors.lastname: Padrón