The determination of the stereochemistry of erythro-1,2-diphenyl-1,2-ethanediol: an undergraduate organic experiment

Using NMR Spectroscopy and Chemical Synthesis to Establish Diastereoselectivity of NaBH4 and Meerwein–Ponndorf–Verley (MPV) Reduction of (±)-Benzoin Isopropyl Ether: A Collaborative Discovery-Based Laboratory Experiment

“…Pedagogical effectiveness of this experiment was assessed through students' experimental outcomes (their ability to perform the chemical reactions, isolate products in good yield, and establish reaction diastereoselectivities by TLC analysis of each reduction product vs authentic 9), their answers to Scheme 1. Diastereoselective Reduction of (±)-Benzoin (1) to meso-Hydrobenzoin (2) postlab questions (Supporting Information) focused on interpretation of NMR spectra, and their ability to establish relative ratios of 9 to 10 by NMR analysis.…”

“…The development of methods for stereocontrolled reduction of chiral α-hydroxyketones and their hydroxyl-protected derivatives has long been a subject of interest in modern synthetic organic chemistry . Interestingly, a few related pedagogically engaging discovery-based undergraduate organic chemistry lab experiments have also appeared in this Journal . − Rowland described a remarkably illustrative experiment in which (±)-2-hydroxy-1,2-diphenylethanone (also known as benzoin, 1 ) was reduced with NaBH 4 to afford a hydrobenzoin: a vicinal diol with two stereocenters capable of existing as meso and dl diastereomeric forms. The identity of the major diastereomer as meso -hydrobenzoin ( 2 ) with near exclusion of the dl form [diastereomeric excess (de) 100%] was established by 1 H NMR analysis of the acetonide 3 derived from the hydrobenzoin, which displays two well-resolved singlets representing the nonequivalent geminal methyl groups (Scheme ).…”

“…This trend is consistent with the Felkin−Anh model for predicting the preferred diastereoselection in nucleophilic addition to α-chiral carbonyl systems. 5 As a sequel to these stereochemical investigations, and as a follow-up experiment to Rowland's popular NMR investigation on diastereoselective NaBH 4 reduction of benzoin that is a standard second-semester organic lab experiment 2,6 in our lab curriculum, a new collaborative discovery-based undergraduate organic chemistry lab experiment was developed in which students experimentally establish the diastereoselectivity of hydride reduction of the α-chiral ketone (±)-benzoin isopropyl ether to erythro and threo diastereomeric alcohols by two different reducing agents.…”

Preparation of Acetonides from Soybean Oil, Methyl Soyate, and Fatty Esters

“…The resulting acetonide can be readily hydrolyzed to give the diol; 20 the diol can be regenerated to acetonide via FeCl 3 . 21 Thus, the acetonide branching is reversible. Furthermore, acetone is relatively safe and can be removed with less environmental hazard.…”

“…For the cyclic ketal reaction, we have chosen acetone as the reactant because of its low cost and general availability. The resulting acetonide can be readily hydrolyzed to give the diol; the diol can be regenerated to acetonide via FeCl 3 . Thus, the acetonide branching is reversible.…”