Martin reagent

Cleavage of Carbohydrates by Hypervalent Iodine Reagents Starting Material Product Yield 

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The Dess-Martin reagent can be shock sensitive under some conditions and explode > 200°C. Other hypervalent iodine oxidizing reagents are known, including PhI(OAc)2/TEMPO and PhI(OAc)2 supported on alumina with microwave irradiation. 

Oxidation by the Dess-Martin Reagent. Another reagent that has become important for laboratory synthesis is known as the Dess-Martin reagent,28 which is a hypervalent iodine(V) compound.29 The reagent is used in inert solvents such as chloroform or acetonitrile and gives rapid oxidation of primary and secondary alcohols. The by-product, o-iodosobenzoic acid, can be extracted with base and recycled. 

Scheme 12.4 shows several examples of the use of the Dess-Martin reagent. 

Scheme 20. Synthesis of hexacyclic polyether 138. (a) 4.0 equiv of Tebbe reagent (93), THF, 25 °C, 0.5 h then reflux, 10 h, 71% (b) BH3 then H202 (c) Dess-Martin reagent, 60% for two steps (d) TBAF, 60% (e) Et3SiH, BF3.Et20,91% (Nicolaou et al.) [34a]...

Several examples of oxidations by the Dess-Martin reagent are shown in Scheme 12.4. 

The alkanol (0.79 mmol) was added to a 0.16 M solution of the Dess-Martin reagent (2.92 mmol) in CH,CL, and the mixture was stirred at rt for 3 h. The mixture was then diluted with Et20 (20 mL) and poured into 0.26 M Na,S203 (7-fold excess to Dess-Martin reagent, typically 60 mL) in sat. aq NaHCO,. The layers were separated and the organic phase was washed sequentially with sal. aq NaHCO, (2 x 25 mL) and H2() (2 x 25 mL). The combined aqueous washes were then back-cxtracted with Et20 (2 x 50 mL). The combined extracts were dried (MgSG4) and filtered, and the solvent was removed under reduced pressure. The residue was usually the pure product. 

Peptide aldehydes 1 can be synthesized effectively by the oxidation of peptide alcohols 15, which are readily available without racemization by reduction of peptide esters 9 with sodium borohydride-lithium chloride (Scheme 5). The peptide alcohols 15 can be readily oxidized to afford enantiomerically pure aldehydes using Parikh-Doering or Dess-Martin reagents. This route is less popular than the previously described reductive methods due to (1) the sensitivity of the aldehydes to further oxidation, (2) racemization under the reaction conditions, and (3) instability of the products under the reaction conditions. 

Oxidation with Dess-Martin reagent 30 is noteworthy for its simple Discussion... 

During the oxidation, an acid-catalyzed cyclization of the product by attack of the nitrogen atoms on the ketone, leading to three different aminals, must be avoided. A Parikh-Doering oxidation gives a good yield of the desired ketone, while PCC, Dess-Martin reagent and Jones oxidation deliver diverse amounts of aminals. 

Thus, impure samples of Dess-Martin periodinane containing 44 because of partial hydrolysis of Dess-Martin reagent or incomplete acetylation during its preparation can in fact perform much better during the oxidation of alcohols than very pure samples of Dess-Martin periodinane. Likewise, performing the oxidation in the air or using wet solvents may result in better yields because of the in situ generation of periodinane 44. 

Normally, nitrocompounds resist57 the action of Dess-Martin reagent. However, there is one report in which a nitroalcohol is transformed into a lactone, thanks to a very easy intramolecular interaction between the nitro group and the alcohol.58... 

Occasionally, alkenes suffer migrations80 or cis-trans isomerizations6d during Dess-Martin oxidations. Such reactions normally only occur under very favourable thermodynamic and kinetic conditions, Dess-Martin reagent being able to deliver compounds containing unstable alkenes that would isomerize on simple contact with silica. 

A variety of methods have been described to solve the task in solution.16 Common oxidative agents for this transformation include various heavy-metal reagents such as chromium-or ruthenium-based oxides, pyri-dine-S03, and dimethylsulfoxide (DMSO) in combination with acetic anhydride, carbodiimide, or oxalyl chloride for activation. One of the most prominent methods for the reliable conversion of sensitive compounds is the Dess-Martin reagent or its nonacetylated equivalent, 1-hydroxy-(17/)-benzo-l,2-iodoxol-3-one-l-oxide (2-iodoxybenzoic acid, IBX). 

On the contrary, periodinanes [e.g., iodoxo or iodine(V) reagents] are widely employed in the oxidation of sensitive and complex alcohols, preferably as IBX32 33 or its acetylation product, the Dess-Martin reagent.34 Periodinanes have not been prepared on a polymer support so far, although a sihca-supported IBX has been reported recently.35... 

The tris trifluoroacetoxy analog of Dess-Martin reagent is formed from o-iodoxybenzoic acid and trifluoroacetic anhydride. Curiously, no reports about the reactivity of this interesting oxidant are available [65]. 

Mainly iodine(v) reagents have been used for such oxidations, but some iodine(III) reagents have also been successfully applied. The radical TEMPO (2,2,6,6-tetramethyl-l-piperidinyloxyl) is necessary in the oxidation of alcohols with (diacetoxyiodo)benzene 3. With this combination highly selective oxidations of primary alcohols to the corresponding aldehydes in high yields are possible, Scheme 12. Secondary alcohols are not attacked under the reaction conditions providing a useful alternative to the widely used Dess-Martin reagent [71 ]. 

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