Moffat oxidations

The general procedure described here was originally published by the submitters,3 who have used this insoluble reagent to prepare aldehydes and ketones under Moffat oxidation conditions.4 A polymeric reagent offers two advantages (a) when an oxidation is complete, the urea... 

POLYMERIC CARBODIIMIDE. II. MOFFAT OXIDATION 4-tert-BUTYLCYCLOHEXANONE... 

The general procedure described here was originally published by the submitters.3 Both ketones and aldehydes may be prepared, and this method is particularly effective when the mild conditions of the Moffat oxidation are required, but the dicyclohexylurea by-product formed with the usual reagents causes purification problems. 

Mesitylene [Benzene, 1,3,5-tnmethyl-], 86 Z Met Gly Gly OEt [Gly cine,V-[Ar-[A-[(phenylmethoxy)carbonyl] -L-methionyl] glycyl] -, ethyl ester], 9 3 Methane, iodo-, hazard note 127 Methyl chlonde polystyrene [Benzene, diethenyl-, polymer with ethenyl-benzene, chloromcthylatcd], 96 Methyl iodide [Methane, iodo-], 79 Methyl mercaptan [Methanethiol], 73 Moffat oxidation, 99... 

Figure 18 shows a pilot plant with a capacity of 10 t/a built for Swern-Moffat oxidation (Kawaguchi et al. 2006). The microreactor includes a series of rapid mixing functions for mass production. The yield of... 

Ketone 166, the key intermediate of deplancheine was obtained in 63% overall yield by the reaction of harmalane (150) with l-bromo-2,3-epoxypropane, followed by sodium borohydride reduction and Moffat oxidation (116). Methods for the elaboration of the exocyclic, -configurated double bond are reviewed (117). 

MIDETR1ETHYLAMINE, 58, 122 Methyl thiohenzoate, 58, 41,43 Methyl vinyl ketone, 58, 162, 163, 164, 167 Moffat oxidation, 56, 99 Monochloroborane dicthylctherate, 58,... 

In Part A geraniol is oxidized to geranial (citral) by Swern s modification of the Moffat oxidation. 1 The stereoisomerlc purity of the product is at least 98%. This procedure is readily conducted on a large-scale and requires only 4 hours time including distillation of oxalyl chloride. The oxidation of geraniol to pure (E)-geranial may also be accomplished by... 

Then, a pilot plant with a capacity of lOt/a was build for the Swern-Moffat oxidation [57,58]. The yield of the batch process is 83% at — 70 °C, whereas the microchemical process achieved a yield of 88% at 20 °C. The pilot plant was operated under stable reaction conditions for a long run with similar product yields as in the laboratory experiment (see Figure 5.23). 

The use of carbodiimides in organic synthesis includes the Moffat oxidation of primary alcohols to aldehydes using a dicyclohexylcarbodiimide/DMSO adduct as reagent. Also, conversion of alcohols or phenols into hydrocarbons via hydrogenation of acylisoureas derived from the corresponding carbodiimide adducts is a useful reaction. Furthermore, aldoximes, on treatment with carbodiimides, are converted into nitriles, and numerous uses of carbodiimides as condensation agents or catalysts are known (see Chapter 13). 

Utilization of this polymer in peptide synthesis afforded only 60 % peptide, the remainder being the N-acylurea. However, the polymer is useful in the Moffat oxidation (see Section 2.4.3). ... 

The reaction of ylides with carbodiimides usually produces linear 1 1 adducts. The adducts derived from DMSO and carbodiimides undergo a facile reaction with primary alcohols to give an aldehyde (Moffat oxidation). With phenols and carboxyhc acids, alkylation products and esters, respectively, are formed. The oxidation proceeds under mild conditions and can be applied to sensitive compounds. Primary alcohols are oxidized solely to aldehydes without the formation of even trace amounts of carboxylic acids. The carbodiimide adducts generated from DMSO or the dimethylseleniumoxide " adducts have structure 369 (X = S, Se). 

Two syntheses of racemic betalamic acid have been carried out so far. In Dreiding s approach (Scheme 1) (11,90,91), chelidamic acid (62) was used as the starting material. Hydrogenation of 62 with a rhodium catalyst yielded an all-cw piperidine derivative, which was converted to the dimethyl ester 63. The conditions used for the hydrogenation step kept the concomitant removal of the hydroxyl group to a minimum. The oxidation of alcohol 63 to the corresponding piperidone derivative 64 required careful control of the reaction conditions to avoid overoxidation to pyridine derivatives. This was accomplished by use of a polymeric carbodiimide in the Pfitzer-Moffat oxidation, which afforded the desired product 64 in 90% yield. For the introduction of the side chain, a new... 

Enol phosphates of a-ketosulfones provide the key intermediate to alternate schemes leading to acetylenes. Acylation of phenyl sulfones with esters affords the ketone derivatives directly. Alternately, the ketones can be obtained by Moffat oxidation of the condensation products from aldehydes with sulfone anions. Conversion to the enol derivatives followed by treatment with Na/NH or Na(Hg) gives the acetylenes. 

The tritylsulfenamide can be prepared from an amine and the sulfenyl chloride (Na2C03, THF, H2O or Pyr, CH2CI2, 64-96% yield) it is cleaved by hydrogen chloride in ether or ethanol (0°C, Ih, 90% yield), " CuClj (THF, EtOH, 58-67% yield), MeaSil (77-96% yield),I2 (0.1 M, THF, collidine, HjO, 97% yield), BusSnH, 115°C, toluene, 5 min, 82% yield. " The tritylsulfenamide is stable to lA HCl, base, NaCNBHs, L1A1H4, tn-chloroperoxybenzoic acid, pyridinium chloro-chromate, Jones reagent, Collins oxidation and Moffat oxidation. The stability of this group is largely due to steric hindrance. 

Moffat oxidation of amino alcohols with EDC (Scheme 3.5) [20]. 

Moffat oxidation of amino alcohols with EDC(HCl)/DMSO excess EDO and the formed corresponding urea HC1 cation exchange resin anion exchange resincl [20]... 

Pyridine reacts with sulfur trioxide to give the crystalline, zwitterionic pyridinium-1-sulfonate, usually known as the pyridine sulfur trioxide complex. This compound is hydrolysed in hot water to sulfuric acid and pyridine (for its reaction with hydroxide see 8.12.3), but more usefully it can serve as a mild sulfonat-ing agent (for examples see 16.1.1.3 and 18.1.1.3) and as an activating agent for dimethylsulfoxide in Moffat oxidations. 

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