Summary of the preparation of aldehydes and ketones
I. Preparation of aldehydes and ketones by alcohol oxidation
PCC (Pyrindium Chlorochromate) oxidation
PCC can oxidize primary and secondary alcohols to aldehydes and ketones. Due to the reaction in organic solvents, alcohols are generally not oxidized to carboxylic acids. However, when water is present in the reaction system, the resulting aldehydes and ketones form hydrated aldehydes or hydrated ketones, which continue to oxidize to carboxylic acids. Therefore, no water is required in the reaction system.
The oxidation of PCC is mainly a homogeneous reaction, but there are methods to adsorb the catalyst on inorganic carriers such as silica gel, alumina, or organic polymer carriers such as ion-exchange resins, for non-homogeneous catalytic oxidation of alcohols. Post-treatment is simple and can control the selectivity of the reaction.
PDC (pyridinium dichromate) oxidation
Addition of pyridine to an aqueous solution of chromium trioxide produces a bright yellow PDC solid. PDC is soluble in organic solvents and is easy to store and handle in air at room temperature. Alcohols can be oxidized to aldehydes and ketones in a suspension of dichloromethane (similar to the oxidation of PCC, protected by an inert gas to avoid contact with water in the air). PDC with DMF as solvent can oxidize primary alcohols to acids. In addition, 3Å molecular sieves, HOAc, PPTS, PTFA, and Ac2O can speed up the oxidation of PDC. The end of the reaction can be quickly quenched with sodium sulfite.
The oxidizing ability of PDC is stronger than that of PCC, and its oxidation is generally carried out under neutral conditions, while PCC needs to be carried out in acid. Therefore, oxidation of acid-unstable compounds with PCC must be carried out in the presence of sodium acetate.
When PCC or PDC is used alone, a dark brown oily residue is generated along with the reaction. The product is coated with this residue, resulting in a lower yield. Adding diatomaceous earth, silica gel or molecular sieves to the reaction solution can improve the situation.
Jones Oxidation (Jones Reagent Oxidation)
Jones oxidation (Jones reagent oxidation) is the reaction in which chromic acid oxidizes primary and secondary alcohols to carboxylic acids and ketones, respectively, in acetone.Jones reagent (Jones reagent), an aqueous solution of chromium trioxide, sulfuric acid, and water…
Dess-Martin periodontane oxidation.
Reaction in which alcohols are oxidized to their corresponding carbonyl compounds using triacetoxyhomoiodane.Dess-Martin homoiodane, 1,1,1-triacetoxy-1,1-dihydro-1,2-phenyliodono-3(1H)-one, is a very efficient oxidizing agent that oxidizes secondary and primary alcohols to aldehydes and ketones, respectively.The reaction is carried out with the help of a reagent called Dess-Martin’s reagent (Jones’ Reagent), a solution of chromium trioxide with sulfuric acid in water.The reaction is carried out with the help of the reagent, which is a solution of chromium trioxide in water.
IBX Oxidation reaction IBX Oxidation
IBX oxidation is an oxidation reaction with relatively mild reaction conditions and a wide range of substrates. The disadvantages are the solubility of IBX in organic solvents and the instability of high-valent iodine.
