Sodium ozonide reduction with

The determination of the active oxygen in ozonides with sodium iodide in glacial acetic acid gives reliable values only in the case of ketozonides. The reaction products are ketones.96 Iodometric peroxide determination in the case of aldozonides gives less than 60% of the theoretical value 112 carboxylic acids are formed as well as aldehydes. The reduction with iodide ions probably suffers competition from the reaction shown in Eq. (7). 

Ozonides are rarely isolated [75, 76, 77, 78, 79], These substances tend to decompose, sometimes violently, on heating and must, therefore, be handled with utmost safety precautions (safety goggles or face shield, protective shield, and work in the hood). In most instances, ozonides are worked up in the same solutions in which they have been prepared. Depending on the desired final products, ozonide cleavage is done by reductive or oxidative methods. Reductions of ozonides to aldehydes are performed by catalytic hydrogenation over palladium on carbon or other supports [80, 81, 82, S3], platinum oxide [84], or Raney nickel [S5] and often by reduction with zinc in acetic acid [72, 81, 86, 87], Other reducing agents are tri-phenylphosphine [SS], trimethyl phosphite [89], dimethyl sulfide (DMS) [90, 91, 92], and sodium iodide [93], Lithium aluminum hydride [94, 95] and sodium borohydride [95, 96] convert ozonides into alcohols. 

The starting material is ergocalciferol, the triene system and alcohol group of which are protected as a sulfur dioxide adduct and a silyl ether, respectively. The side-chain is degraded by ozonolysis at -10 °C in dichloromethane. Direct reduction with sodium borohydride destroys the ozonide and reduces the aldehyde to the alcohol. The yield amounts to 87 %. 

Catalytic hydrogenation114-116 also leads to carbonyl compounds, acids being formed in a side reaction.110 Reduction of the ozonides with lithium aluminum hydride117 119 and with sodium borohydride119 yields alcohols. 

Reducing agents can be used, but most convert the ozonide to an alcohol rather than to a carbonyl. Reduction of the ozonide with lithium aluminum hydride or sodium borohydride generates the alcohol products, as expected, by further reducing the intermediate carbonyl products. It is noted that 1 mol of L1A1H4 is required per mole of ozonide and the temperature is usually maintained below The most... 

A novel fragmentation of iV-arylidene- or Al-(aLkylideneamino)- 8-lactams can be induced by ozone to lead to various enol ethers after a reductive workup with sodium borohydride. The starting 8-lactams can be prepared via [2 + 2] cycloaddition of alkoxy ketenes and an azine and upon treatment with ozone at low temperature, yield the expected secondary ozonides (eq 59). Reduction of the ozonide leads to the corresponding N-nitroso intermediate, which is susceptible to fragmentation of the C4—N1 bond to give a zwitterion intermediate that rearranges to yield the product enol ethers. In the reaction sequence, fra 5- 8-lactams yield predominantly the E-enol ether while the d5- 8-lactams preferentially form the Z-configured enol ethers. 

Fig. 8.3 Ozonolysis allows the cleavage of alkene double bonds. According to the Criegee mechanism the primary ozonide (POZ) is rapidly transformed into the more stable secondary ozonide (SOZ). Depending on the work-up, different products may be isolated. Oxidative work-up with hydrogen peroxide leads to carboxylic acids/ketones, while reductive work-up with either dimethyl sulfide or sodium borohydride gives aldehydes/ketones or alcohols, respectively...

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