Ring Opening of Epoxides by Pendant Silanols

Abstract

We present a new ring-opening reaction of epoxides by pendant silanols, catalyzed by either Ph 3 C + BF 4 − or BINOLphosphoric acid. Silanol epoxides derived from trans-allylic alcohols, cis-allylic alcohols, trans-homoallylic alcohols, and cishomoallylic alcohols were all compatible and gave products from either endo-or exo-ring opening. With silanol epoxides derived from 4-alkenyl silanols, an unusual rearrangement to tetrahydrofuran products was observed. The utility of this methodology was demonstrated in a short preparation of protected D-arabitol.

Ring-Opening of Aziridines by Pendant Silanols Allows for Efficient Preparations of (±)-Clavaminol H, (±)-Des-Acetyl-Clavaminol H, (±)-Dihydrosphingosine, and (±)-N-Hexanoyldihydrosphingosine

“…Our work on the ring-opening of epoxides with pendant silanols 25 informed our efforts with their aziridine relatives 37 (Scheme 3). Optimization experiments were performed using di-tert-butyl(2-((2S*,3S*)-3ethyl-1-tosylaziridin-2-yl)ethoxy)silanol, prepared in one step using a Sharpless aziridination of (E)-di-tertbutyl(hex-3-en-1-yloxy)silanol.…”

“…23 Our laboratory has a programmatic focus on the development of the di-tert-butyl-silanol auxiliary into a uniquely reactive functional handle. [24][25][26][27][28][29] We envisioned a ring-opening of aziridines by pendant di-tert-butyl silanol auxiliaries, which would afford protected amino alcohols in a single transformation. Here, we show our development of this reaction, and its application in the rapid assembly of select natural products and analogues.…”

Ring Opening of Aziridines by Pendant Silanols Allows for Preparations of (±)-Clavaminol H, (±)-Des-Acetyl-Clavaminol H, (±)-Dihydrosphingosine, and (±)-N-Hexanoyldihydrosphingosine

“…Temporary tethering using Lewis acid templates affords excellent regiocontrol with epoxides, − but only one such report exists with aziridines . Our laboratory has a programmatic focus on the development of the di- tert -butyl-silanol auxiliary into a uniquely reactive functional handle. − We envisioned a ring opening of aziridines by pendant di- tert -butyl silanol auxiliaries, which would afford protected amino alcohols in a single transformation. Here, we show our development of this reaction, and its application in the rapid assembly of select natural products and analogues.…”

Highly Regio- and Stereoselective Intramolecular Rearrangement of Glycidol Acetal to Alkoxy Cyclic Acetals

“…Among the oxiranes, 2,3-epoxy alcohols (glycidols) are of specific importance; the hydroxyl group serves as a handle to direct the ring-opening reactions in a highly regio- and stereoselective manner . Additionally, the hydroxyl group binds to different functional groups, allowing for highly selective intramolecular ring-opening reactions . A large variety of nucleophiles (C, H, N, O, X, S, P, etc.)…”