Ozone, cleavage with

Ozone. Most acetals are subject to cleavage with ozone, giving a mono ester of the original diol. 

Stearolic acid, C H- Oa, yields stearic acid on catalytic hydrogenation and undergoes oxidative cleavage with ozone to yield nonanoic acid and nonanedioic acid. What is the structure of stearolic acid ... 

Now we must apply some reverse reasoning. What alkene will produce these two aldehydes upon cleavage with ozone The two carbons of the carbonyl groups of these aldehydes (the blue carbons) must have been doubly bonded together in the original alkene. Therefore, the unknown alkene must be 2-pentene ... 

These amines can be deprotected under reduction conditions (Pd-C/R0H/HC02NH4 or Na/NH3). The allyl amines can be deprotected by oxidative cleavage with ozone (dimethyl-sulfide work up) or with KMn04 in acetone. 

One method of oxidative cleavage relies on a two-step procedure using ozone (O3) as the oxi-flant in the first step. Cleavage with ozone is called ozonolysis. 

Diols are oxidatively cleaved by reaction with periodic acid (HIO4) to yield carbonyl compounds, a reaction similar to the KMnO cleavage of aJkenes just discussed. The sequence of (1) alkene hydroxylation with OsO< j followed by (2) diol cleavage with HIO4 is often an excellent alternative to direct alkene cleavage with ozone or potassium permanganate. 

When the donor character of the amino substituent at the transition-metal-carbene carbon atom is reduced, it should be possible to influence the thermal stability and reactivity in favor of the desired cyclopropanation process. Indeed, pyrrol-1 -ylcarbene complexes 18 of chromium, molybdenum and tungsten do exhibit the desired reactivity. In the last step, the pyrrole ring of 19 can be converted to the NH2 function in 20 after oxidative cleavage with ozone.In this respect, the pyrrole heterocycle represents a synthetic equivalent of the amino function. 

Azelaic Acid from Vegetable Feedstock via Oxidative Cleavage with Ozone or Oxygen... 

I 20 Azelak Acid from Vegetable Feedstock via Oxidative Cleavage with Ozone or Oxygen Table 20.1 Comparison of different approaches for the synthesis of AA. 

This chapter will define an oxidation in general terms. Various reagents will be introduced that oxidize an alcohol to an aldehyde or to a ketone. In some cases, alcohols may be oxidized to a carboxylic acid. Oxidation of alkenes will be revisited—specifically, for the oxidation of an alkene to an oxirane or to a 1,2-diol. Oxidative cleavage with ozone will be revisited, and new methods for oxidative cleavage will be introduced. 

The new hydrazones were first tested in simple a-alkylation reactions. As is shown in scheme 14, metalation with Lochmann-Schlosser base in THF at low temperature yielded highly reactive azaenolates, which were alkylated by a number of alkyl halides at -100°C in good yields and with high diastereomeric excess (de = 85 - > 95%). It is noteworthy that, besides the usual oxidative cleavage with ozone, the SAMP-hydrazones could be converted without racemization to the final 3-substituted 2-oxoesters under very mild conditions with boron trifluoride-ether in acetone/water with the addition of paraformaldehyde. Thus, this method permitted for the first time the highly enantioselective transfer of a homologous pyruvate unit to electrophiles (scheme 14) [41]. 

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