Cleavage oxidative

Oxidative Cleavage. Rate constants relative to that of neopentane have been measured for the reactions of ( Dj) atoms with alkanes and cycloalkanes and were found to be simply proportional to the number of CH bonds in the hydrocarbon but independent of their type or strength.  

Whereas the three-membered ring of (432) is very sensitive to attack by chromyl chloride, (433) is much less reactive, and under forcing conditions is oxidized to anthraquinone.  

Chromic acid oxidation of 1-substituted cycloalkanols (434 m = 0,1,..n = 1,2, 3. ..) proceeds with ring-cleavage, giving keto-acids. Lead tetra-acetate oxidation of the cyclobutanol (435) has been reported to take an unusual course, giving in addition to the expected y-hydroxy-ketone (436) the new compound (437), whose structure was confirmed by X-ray analysis. 

A new route to P-dicarbonyl compounds involves the lead tetra-acetate oxidation of 2-aminocyclopropanols.  

Selenium dioxide oxidation of cyclobutanone may lead to y-btityrolactone or cyclopropanecarboxylic acid, depending on the reaction conditions, but thallium(iii) oxidation gives only ring-contraction. Thallium(iii) or mercury(ii) oxidation of methyl-enecyclopropane gives rise to butan-2-one or its derivatives by ring-cleavage. ° 

Oxidative Cleavage, Full details on the oxidation of cyclopropanols by chromic acid have now appeared.  

Oxygenation of appropriate cyclopropane derivatives can now be brought about. Using the metal-ion-catalysed procedure, (191) is converted into epoxyketone (192X 

The ring cleavage of mono-, di-, and tri-phenylcyclopropanes by mercuric acetate becomes more difficult as the number of phenyl substituents is increased, with substitution in the aryl ring occurring almost exclusively for (197 = Ph  

Some aryl-substituted cyclopropanes have also been subjected to oxy-mercuration by the same school. The stereoselectivity observed in the cleavage of (201) 

Hiyama, H. Koide, and H. Nozaki, Bull. Chem. Soc. Japan, 1975,48,2918. 

Ozonation. Alkenes react readily with ozone to give oxidized compounds via cleavage of the n or the J,n bonds.582-592 Ozonides, the direct product of the reaction, are rarely isolated but are transformed in situ into synthetically useful products. Depending on the solvent used and the actual workup of the reaction mixture different products may be isolated.582-584,592 Although its use is inconvenient, ozone is widely employed in selective syntheses. A classical use of ozone is in the structure determination of natural compounds and polymers. 

The first normal ozonide, the ozonide of 1,2-dimethylcyclopentene, was isolated and characterized as early as 1953 by Criegee.597 Ozonides were later observed by 

The highly reactive carbonyl oxide could be trapped by added carbonyl com-pounds to form normal ozonides. Isolation of dimeric (77) and polymeric 

In agreement with the Criegee mechanism, unsymmetric alkenes,606,607 such as 2-pentene606 [Eq. (9.108)], or a pair of symmetrical olefins, such as a mixture of CH2=CH2 and CD2=CD2,608 yield three different ozonides, including two symmetric cross-ozonation products (80, 81)  

MeHC CHEt + MeHC CHMe + EtHC CHEt (9.108) 

Starting (co)polymer Exp. conditions Postozonitation treatment Refs. 

Poly(l-4 isoprene) Inert solvent (- 70 to 30 °C) Reduction with LiAlH4 [370] 

Acrylonitrile-butadiene copolymer Tetrahydrofuran 15 °C Reduction with Na borohydrides [371] 

Poly(isobutylene) Cyclohexane Reduction with Eb/Ni Raney [372] 

Poly(butene) Suspension in hexane Reduction with Ni Raney [373,374] 

There are many reagents that will add across an alkene and completely cleave the C=C bond. In this section, we will explore one such reaction, called ozonolysis. Consider the following 

Notice that the (Z=C bond is completely split apart to form two C=0 double bonds. Therefore, issues of stereochemistry and regiochemistry become irrelevant. In order to understand how this reaction occurs, we must first explore the structure of ozone. 

Ozone is a compound with the following resonance structures  

The role of ozone in atmospheric chemistry is discussed in Section 11.8. 

Ozone is formed primarily in the upper atmosphere where oxygen gas (O2) is bombarded with ultraviolet light. The ozone layer in our atmosphere serves to protect us from harmful UV radiation from the sun. Ozone can also be prepared in the laboratory, where it can serve a useful purpose. Ozone will react with an alkene to produce an initial, primary ozonide (or molozonide), which undergoes rearrangement to produce a more stable ozonide  

---

Oxidative cleavage of the complex 549 with CuCri affords 2,3-bis(chloro-methyl)-1,3-butadiene (550) and regenerates PdCri. Thus the preparation of this interesting dimerization product 550 can be carried out with a catalytic amount of PdCl2 and two equivalents of CuCb in MeCN[495], Similarly, treatment of allene with PdBr2 affords the dimeric complex 551. Treatment of this complex with 2 equiv, of bromine yields the dibromide 552. The tetra-bromide 553 is obtained by the reaction of an excess of bromine[496]. Similarly,... 

A reaction characteristic of vicinal diols is their oxidative cleavage on treatment with periodic acid (HIO4) The carbon-carbon bond of the vicinal diol unit is broken and two carbonyl groups result Periodic acid is reduced to iodic acid (HIO3)... 

The oxidation may be carried out with an inert solvent thermally (35), with a sensitizer such as bromine (36), with uv radiation (37), or over a suitable catalyst (38). Principal by-products of all these oxidation processes are the acyl fluoride products derived from oxidative cleavage of the perfluoroaLkene (eq. 

Oxidative cleavage of P-aminoacyl complexes can yield P-amino acid derivatives (320,321). The rhodium(I)-catalyzed carbonylation of substituted aziridines leads to P-lactams, presumably also via a P-aminoacyl—metal acycHc compound as intermediate. The substituent in the aziridine must have 7T or electrons for coordination with the rhodium (322,323). 

The diacids for these polymers are prepared via different processes. A2elaic acid [123-99-9] for nylon-6,9 [28757-63-3] is generally produced from naturally occurring fatty acids via oxidative cleavage of a double bond in the 9-position, eg, from oleic acid [112-80-1] ... 

---