Corey Schmidt Oxidation

The Corey-Schmidt oxidation, developed by E.J Corey and Greg Schmidt, is a method used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones using pyridinium dichromate (PDC), also known as the Cornforth reagent.1

Oxidation Variations

Here you can find the various types of Oxidation conditions and reagent combinations that utilize Corey-Schmidt Oxidation.

In the original paper "Useful procedures for the oxidation of alcohols involving pyridinium dichromate in aprotic media." by Corey & Schmidt (1979), they discovered a novel method using pyridinium dichromate (PDC), used to convert primary alcohols to aldehydes and secondary alcohols to ketones.1

PDC with DMF as a solvent can selectively oxidize a multitude of different functional groups and compounds. Here are a brief list of what it can oxidize:

Primary and Secondary Alcohols

In the original paper "Useful procedures for the oxidation of alcohols involving pyridinium dichromate in aprotic media." by Corey & Schmidt (1979) reported that PDC/DMF can be used to readily oxidize non-conjugated primary alcohols to carboxylic acids at 25°C.1

Additionally, Corey & Schmidt reported that PDC/DMF can be used to oxidize secondary alcohols to Ketones.1

Other Conversions

There are also more additional uses for this reagent combination such as allowing for Aldehydes to be converted to Carboxylic Acids.2

Next, PDC in DMF can oxidize tertiary allylic alcohols can be converted to enones. Additionally, allylic positions in alkenes to enones.2

Lactols to Lactones

Lastly, Lactols (Acetals) can also be converted to Lactones under mild conditions as seen in the paper "Total Synthesis of Oxidized Phospholipids. 3. The(11E)-9-Hydroxy-13-oxotridec-11-enoate Ester of 2-Lysophosphatidylcholine" by Deng et al. (2000) where (PDC) (1.35 g, 3.6 mmol) in DMF (5 mL) was stirred at room temperature for 20 h,3

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Oxidation with DCM

Pyridinium dichromate

This section briefly goes over Pyridinium dichromate in detail ranging from definition to preparation.

PDC is a stable, bright orange solid soluble in various organic solvents, including DMF and DCM, which allows for anhydrous conditions. It offers advantages over PCC for acid-sensitive substrates, providing high selectivity and effectiveness under mild conditions suitable for complex and sensitive molecules.1

Reagent Breakdown

This section briefly details the structure of Pyridinium dichromate.

Reagent Preparation

This section details the preparation method used to create Pyridinium Dichromate in the original 1979 paper by Corey and Schmidt.

In their 1979 paper, E. J. Corey and Greg Schmidt introduced a method for preparing Pyridinium Dichromate (PDC), a useful reagent for the oxidation of alcohols in aprotic media. The process is straightforward, involving the dissolution of Chromium Trioxide in water, addition of pyridine, and crystallization. Below is a detailed step-by-step guide based on their original publication.

Chromic Acid Formation

To begin, 100 g (1 mol) of Chromium Trioxide (CrO₃) is dissolved in 100 ml of water (H₂O). This step must be conducted at a temperature below 30°C to ensure complete dissolution and stability of the solution.

Product Formation

In the second step, 80.6 ml of pyridine (C₅H₅N) is gradually added to the chromic acid solution while maintaining the temperature between 0 and 30°C. This reaction leads to the formation of pyridinium chromate initially, which then further reacts to form pyridinium dichromate (PDC) and water as a byproduct.

Post Formation

The resulting solution is then diluted with 400 ml of acetone and cooled to -20°C, causing the bright orange crystals of PDC to precipitate. These crystals are collected by filtration, washed with acetone, and dried in vacuo to yield the final product, pyridinium dichromate.

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Oxidation with DCM

References

1. Corey, E. J.; Schmidt, G. Useful Procedures for the Oxidation of Alcohols Involving Pyridinium Dichromate in Aprotic Media. Tetrahedron Lett. 1979, 20 (5), 399–402. DOI: 10.1016/S0040-4039(01)86498-0. ↩

3. Deng, Y.; Salomon, R. G. Total Synthesis of Oxidized Phospholipids. 3. The (11E)-9-Hydroxy-13-oxotridec-11-enoate Ester of 2-Lysophosphatidylcholine. J. Org. Chem. 2000, 65 (20), 6660-6665. DOI: 10.1021/jo000809u. ↩