In recent years, organic high-valent iodine compounds have been widely used in modern organic synthetic chemistry as a new organic synthesis reagent that is easy to prepare, mild in performance, high in selectivity, and environmentally friendly. One of the most widely used reagents. At the same time, Dess-Martin Oxidation is a common oxidation reaction in modern organic synthesis. Dess-Martin oxidant is a commonly used, mild and selective oxidation reagent, often used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. Its advantages are mild reaction conditions, moderate speed, low dosage and simple post-treatment. The preparation method can be obtained by oxidizing the cheap ortho-iodobenzoic acid with potassium bromate in a sulfuric acid solution of appropriate concentration to form a compound, which is then treated with acetic anhydride to obtain Dess-Martin periodinane reagent.
1. The nature of DMP
Dess-Martin Periodinane (Dess-Martin Periodinane) is abbreviated as DMP. Alias: 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3 (1H) -one Molecular formula / Molecular weight: C13H13IO8 = 424.14. At 25 ° C, Dess-Martin oxidant is white flake or bulk crystal. Its melting point is 130-133 ° C. Boiling point is 40 ° C, density is 1.369 g / mL.
2. Preparation of DMP:
2.1 Traditional synthesis process of Dess-Martin oxidant:
Dess-Martin oxidant is a very famous reagent in organic synthesis. It is generally obtained by co-heating its precursor IBX and acetic anhydride in acetic acid. Its synthesis method is shown in the following figure:
2.2 The specific synthesis of Dess-Martin oxidant [1]
The compound is obtained by oxidizing the cheap ortho-iodobenzoic acid with potassium bromate in an appropriate concentration of sulfuric acid solution to form a compound, which is then treated with acetic anhydride to obtain Dess-Martin periodinane reagent. The specific operations are as follows:
first step:
Add 730 ml of 0.73M sulfuric acid to a 2L clean flask, and carefully add 85.2 g of o-iodobenzoic acid [CAS: 88-67-5] while stirring; while maintaining vigorous stirring and temperature below 55 ° C, be careful 76 grams of potassium bromate was added. After the addition, let it rise to 65 ° C and stir for 3.6 hours. Cool to 0 ° C, filter, and wash with 1000 mL of deionized water, then with 50 mL × 2 of ethanol, and dry to obtain 89 g of Compound 1 (93%).
The second step:
In a 1 L round-bottom flask, add 400 ml of acetic anhydride and 0.5 g of p-toluenesulfonic acid containing one crystal water. Then, 100 g of Compound 2 was carefully added thereto with stirring. Insert the drying tube, warm to 80 ° C and stir for 2 hours. Cool to 0 ° C, filter, and wash 50 mL × 5 times with anhydrous ether to obtain 138 g (91%) of white crystalline solid, namely Dess-Martin high iodine reagent.
3. Dess-Martin Oxidation
The reaction between a substance and oxygen is called oxidation; the effect of getting electrons is called reduction. Oxidation in the narrow sense refers to the combination of substances and oxidation; reduction refers to the loss of oxygen by substances. The oxidation value increases during oxidation; the oxidation value decreases during reduction. Both oxidation and reduction refer to reactants (molecules, ions or atoms). Oxidation is also called oxidation or oxidation reaction. When organic matter reacts, the function of introducing organic matter into oxygen or removing hydrogen is called oxidation; the effect of introducing hydrogen or losing oxygen is called reduction. Dess-Martin Oxidation is a commonly used oxidation reaction in modern organic synthesis. [2] The reaction mechanism is shown in the following figure:
4. High iodine reagent
The high iodine reagent is a type of oxidant that contains high valence iodine (+3 to +5 valence) in the molecule, and oxidizes the reaction substrate with moderate oxidizability of iodine. Compared with trivalent iodine compounds, pentavalent iodine reagents are not widely reported in the literature in terms of quantity or development intensity, but as mild and highly selective oxidants, such reagents are getting more and more The more applications [2]. Common iodine reagents such as inorganic oxidants are iodic acid (Iodic Acid, IAl, iodine Pentoxide, IP); organic oxidants are iodylbenzene (Idoxybenzene, IB), o-iodoxy.benzoic acid , IBX), Dess. Martin periodinane (DMP).
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