The silylalkyne-Prins cyclization: stereoselective synthesis of tetra- and pentasubstituted halodihydropyrans.
[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.
Miranda
Pedro O
PO
Instituto Universitario de Bio-Organica "Antonio Gonzalez", Universidad de La Laguna, C/Astrofísico Francisco Sanchez 2, 38206 La Laguna, Tenerife, Spain.
Ramírez
Miguel A
MA
Martín
Víctor S
VS
Padrón
Juan I
JI