Hydrogenation of Sugar Enol-Ethers Using Pd/Et₃SiH Reagent System: A Route to Deoxy Sugars/Glycosides

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.

Overview
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.

Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.

An oxygen-based nucleophile, like water, can undergo addition reactions with aldehydes and ketones. The reaction leads to the formation of hydrates, also referred to as 1,1-diols or geminal diols.
The formation of hydrates is a reversible reaction. Hydrate formation is influenced by steric and electronic factors accompanying the alkyl substituents on the carbonyl group: The rate of hydrate formation increases with a decrease in the number of alkyl groups attached to the carbonyl carbon. Hence,...

This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy aldehyde formed in a base-catalyzed aldol addition reaction dehydrates on heating to yield an unsaturated carbonyl product, which is commonly referred to as an enal.

Esters are reduced to primary alcohols when treated with a strong reducing agent like lithium aluminum hydride. The reaction requires two equivalents of the reducing agent and proceeds via an aldehyde intermediate.
Lithium aluminum hydride is a source of hydride ions and functions as a nucleophile. The mechanism proceeds in three steps. Firstly, the nucleophilic hydride ion attacks the carbonyl carbon of the ester to form a tetrahedral intermediate. Subsequently, the carbonyl group re-forms,...