jo5026942_si_002.cif (665.93 kB)
Stereoconvergent [1,2]- and [1,4]-Wittig Rearrangements of 2‑Silyl-6-aryl-5,6-dihydropyrans: A Tale of Steric vs Electronic Regiocontrol of Divergent Pathways
dataset
posted on 2015-12-17, 06:59 authored by Luis M. Mori-Quiroz, Robert E. MaleczkaThe regiodivergent ring contraction
of diastereomeric 2-silyl-5,6-dihydro-6-aryl-(2H)-pyrans
via [1,2]- and [1,4]-Wittig rearrangements to
the corresponding α-silylcyclopentenols or (α-cyclopropyl)acylsilanes
favor the [1,4]-pathway by ortho and para directing groups in the aromatic appendage and/or by sterically
demanding silyl groups. The [1,2]-pathway is dominant with meta directing or electron-poor aromatic moieties. Exclusive
[1,2]-Wittig rearrangements are observed when olefin substituents proximal to the silyl are present. cis and trans diastereomers exhibit different reactivities, but
converge to a single [1,2]- or [1,4]-Wittig product with high diastereoselectivity
and yield.