Oxidation with Pyridinium Chlorochromate PCC

To a stirred suspension of 32.3 g (0.1 mol) of pyridinium chlorochromate in 200 mL of methylene chloride is added rapidly at room temperature a solution of 11.6 g (0.1 mol) of 1-heptanol in 100-150 mL of dichloromethane. A black precipitate is formed shortly. After 2 h, the mixture is diluted with 5 volumes of anhydrous ether, the solvents are decanted, and the black solid is washed twice with ether. The organic solution is filtered through Florisil (magnesium silicates), and the solvent is evaporated at reduced pressure. Heptanal (10.1 g), bp 153 °C , is obtained in 78% yield. 

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The pyranocoumarin 105 can be prepared via a three-component Diels-Alder reaction between 4-hydroxycoumarin, ethyl vinyl ether and an a-dicarbonyl compound. Similarly to the above, upon treatment of 105 with sulfuric acid in THF, hydrolysis and rearrangement occur to give the furofurochromenone 106. The hemiacetal functionality in 106 may then be oxidized with pyridinium chlorochromate (PCC) to give the lactone 107 <2001EJ03711> (Scheme 28). 

A novel one-pot tandem oxidation-cyclization-oxidation process was successfully applied in the transformation of unsaturated alcohols 250 [Eq. (5.315)].860 The intermediate aldehyde formed by oxidation with pyridinium chlorochromate (PCC) undergoes a carbonyl-ene cyclization followed by an additional oxidation to form 3-substituted piperidinones. 

The secondary alcohol is readily oxidized with pyridinium chlorochromate (PCC)25 (65) which is commercially available or easily prepared by addition of pyridine to a solution of chromium(VI)-oxide in hydrochloric acid. 

Step 2 Oxidation with pyridinium chlorochromate (PCC) affords the aldehyde. Step 3 Wittig reaction provides the TM. (Note The ylide reagent is prepared by treating Ph3P with CD3I to obtain Ph3P+CD3 r and followed by deprotonation with w-BuLi.)... 

Further processing of 57 towards the ketone 60 is readily effected by highly regioselective tosylation of the primary hydroxyl group (66), hydride reduction 58 -> 59, and oxidation with pyridinium chlorochromate (PCC) on aluminum oxide to afford 60 in a yield of 70 % over the three steps (63). Due to the now practical accessibility of these furanoid building blocks supplementary modifications, that have already been performed, become preparatively relevant, e. g. the conversion of tosylate 58 into the 5,6-epoxide (66), C-extensions (63, 66), shortening of the carbon chain via periodation of 57 (63), and transformation of the respective products into acyclic derivatives by acid hydrolysis of the 1,2-0-isopropylidene group (63, 66). 

Oxidations with pyridinium chlorochromate PCC and pyridinium dichromate PDC. 4 Oxidations with PCC and PDC of secondary hydroxyl groups of sugars and nucleosides is slow and incomplete. The reaction is markedly catalyzed by 3 A molecular sieves. Celite, alumina, and silica are not effective. CH2C12 is the most satisfactory solvent oxidations are slower in C1CH2CH2C1 and C6H5. The rate of oxidation increases in the order 5A<10A<4A<3 A. 

A short-step synthesis of l-oxoeudesma-2,4-dien-l l)3i/-12,6a-olide (65), a sesquiterpene lactone isolated from Artemisia herba-alba, has been devised by Kawamata and coworkers [19]. The synthesis (Scheme 9) involved the reduction of santonin to compounds 36a and 36b and their oxidation with pyridinium chlorochromate (PCC) in CH2CI2 to give 9% of the rearranged product 65 and 30% of santonin. This procedure... 

Q 4. Citronellol I on oxidation with pyridinium chlorochromate (PCC) followed by treatment with aq. sodium hydroxide gives the product II (IR 1680 cm ) whereas oxidation with PCC in the presence of sodium acetate gives product III (IR 1720 cm ). Compounds II and III are ... 

The alcohol citronellol is a terpene found in rose oil. The product formed when citronellol is oxidized with pyridinium chlorochromate (PCC)... 

The synthesis is simply the reverse of the disconnection process, so alkene 139 is converted to alcohol 140 via oxymercuration-demercuration (Chapter 10, Section 10.4.5), and oxidation with pyridinium chlorochromate (PCC Chapter 17, Section 17.2.3) leads to the requisite ketone. Treatment of the ketone with LDA to form the kinetic enolate (note the kinetic control conditions) is followed by addition of propanal and hydrolysis to give the final target, 138. 

We could not deprotect the sulfonamide in the presence of the alcohol group. It was necessary to oxidize with pyridinium chlorochromate (PCC) first, then deprotect the ketone to give sulfonamide S2-... 

These objectives have spurred research directed toward developing alternative synthetic methods. Take alcohol oxidation, for example. As described in Section 15.9, primary alcohols are converted to aldehydes by oxidation with pyridinium chlorochromate (PCC). 

Reductive Silylation ofp-Qninones. Me6Si2 in combination with a catalytic amount of iodine converts /7-quinones (30) into l,4-bis(trimethylsiloxy)arenes (31) in almost quantitative yields (eq 15). The products are a protected form of quinones, which are regenerated by oxidation with pyridinium chlorochromate (PCC)P... 

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