Related Experiment Video
Updated: May 13, 2026

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile
Published on: October 30, 2018
Westphalen's diol diacetate: 19(10→5)-abeo-5β-cholest-9-ene-3β,6β-diyl diacetate
Johana Ramírez Hernández1, Jesús Sandoval-Ramírez, Socorro Meza-Reyes
1Benemérita Universidad Autónoma de Puebla, Facultad de Ciencias Químicas, Ciudad Universitaria, Puebla, Pue. 72570, Mexico.
Abstract:
THE STRUCTURE OF THE TITLE STEROID [ALTERNATIVE NAME: 3β,6β-diacet-oxy-5β-methyl-19-norcholest-9(10)-ene], C31H50O4, confirms the generally accepted mechanism for the rearrangement of a cholestan-5α-ol derivative reported a century ago by Westphalen. The methyl group at position 10 of the starting material migrates to position 5 in the steroidal nucleus, while a Δ(9) bond is formed, as indicated by the C=C bond length of 1.347 (4) Å. The methyl transposition leaves the 5R configuration unchanged, with the methyl oriented towards the β face. During the rearrangement, the steroidal B ring experiences a conformational distortion from chair to envelope with the C atom at position 6 as the flap. In the title structure, the isopropyl group of the side chain is disordered over two positions, with occupancies of 0.733 (10) and 0.267 (10). The carbonyl O atom in the acetyl group at C3 is also disordered with an occupancy ratio of 0.62 (4):0.38 (4).
Related Concept Videos
Preparation of Diols and Pinacol Rearrangement
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis
UV–Vis Spectroscopy: Woodward–Fieser Rules
Aldehydes and Ketones to Alkenes: Wittig Reaction Mechanism
The reaction begins with the nucleophilic addition between a phosphorus ylide and the carbonyl compound. Due to its carbanionic character, phosphorus ylide acts as a strong nucleophile and attacks the electrophilic carbonyl group. This generates a charge-separated dipolar intermediate called betaine. The negatively charged oxygen atom and...
