Alkenes, ozonolysis

Reaction of 3,5-disubstituted-1,2,4-trioxolanes (89) with oxidants (usually under basic conditions) leads to carboxylic acids (Equation (14)). This reaction is often carried out as the work up procedure for alkene ozonolysis, avoiding the need to isolate the intermediate ozonide. Typical oxidants are basic hydrogen peroxide or peracids and this type of oxidative decomposition is useful for both synthetic and degradative studies. 

Neeb, P., F. Sauer, O. Horie, and G. K. Moortgat, Formation of Hydroxymethyl Hydroperoxide and Formic Acid in Alkene Ozonolysis in the Presence of Water Vapour, Atmos. Environ., 31, 1417-1423 (1997). 

As it is well known, acyloxy, alkoxy, or phenoxy groups connected to sp2-hybridized carbon atoms in alkenes or aromatics are unreactive to nucleophilic substitution. However, after alkene ozonolysis such groups become attached to sp3-hybridized carbon atoms and become reactive. It was shown <1989TL1511> that such substitutions have to be carried out at 40 °C when they compete with thermolytic reactions of the ozonides, lowering the yields. However, if 2,3-dichloropropene and as- or /ra/rt-1,2,4-trichloro-2-butene are ozonized, one obtains stable ozonides 68a-70... 

The two-carbon chain elongation of protected D-glyceraldehyde (R)-24 and (R)-62 can be realized via ( -7-alkoxyallylboronate additions, followed by alkene ozonolysis. The allylboronate 162 generated in situ adds to (R)-62 giving a single stereoisomer 163, which can be converted to D-arabinose derivatives following ozonolysis (Scheme 13.57). Similarly, 164 added to (R)-24 gave a major adduct 165 that was then converted into 2-0-methyl-D-arabinose derivatives [105]. 

Two-carbon chain elongation of protected D-glyceraldebyde R)-37 and R)-99 can be realized via ( )-)/-alkoxyallylboronate additions, followed by alkene ozonolysis, furnishing D-arabi-nose derivatives [300]. 

An efficient and straightforward synthesis of isomers of DMDP 36 (2,5-dihy-droxymethyl-3,4-dihydroxypyrrolidine), a known naturally occurring glycosidase inhibitor, has been recently reported. o-Xylose is converted into nitrone 37 in a few steps. Vinylation of 37 gives hydroxyamine 38 which is reduced into the corresponding pyrrolidine with zinc. N-Protection, alkene ozonolysis, and reduction with NaBH4 lead to compound 39. Final deprotection gives 2,5-dideoxy-2,5-imino-L-mannitol (e f-36) (Scheme 14) [92]. 

Methyl esters by degradation of alkenes Ozonolysis of mono-, di-, and trisub-stituted alkenes in methanolic NaOH affords methyl esters. 

Aldehydes can be converted to peroxy acids via ozonation in methyl or ethyl acetate, or to methyl esters via ozonation in 10% methanolic KOH (eq 36). Ethyl esters can be produced analogously, but the use of higher alcohols results in low KOH solubility and poor conversion. This problem can be overcome by adding the aldehyde to a solution of lithium alkoxide in THE at —78 °C and treating this mixture with ozone (eq 37). Additionally, the direct preparation of methyl esters can be accomplished via alkene ozonolysis in methanolic NaOH or by addition of NaOMe to a MeOH-CH2Cl2 ozonolysis solvent system. ... 

SOA material formed by either pathway may be surface-active. For example, organic acids including c -pinonic acid, which is formed via the oxidation of the biogenic VOC a-pinene, are traditional SOA products which have been shown to be surface-active [92-96]. Alkene ozonolysis has also been shown to yield water-soluble surface-active organic compounds [97]. 

Asa-Awuku A, Nenes A, Gao S, Elagan RC, Seinfeld JH (2010) Water-soluble SOA from alkene ozonolysis composition and droplet activation kinetics inferences from analysis of CCN activity. Atmos Chem Phys 10 1585-1597... 

Ozonide A compound formed by the reaction of ozone with an alkene. Ozonolysis Ozone-induced cleavage of a carbon-carbon double or triple bond. 

Orzechowska, G.E., Nguyen, H.T., and Paulson, S.E., Photochemical sources of organic acids. 2. Formation of C5-C9 carboxylic acids from alkene ozonolysis under dry and humid conditions using SPME, J. Phys. Chem., 109, 5358, 2005. 

Alkene ozonolysis and diol cleavage—added in Section 8.8... 

A modification to the alkene ozonolysis reaction employs dimethyl sulphide to reduce the ozonide to a keto-aldehyde. Decomposition of benzoyl poroxide is accelerated by aliphatic sulphides or disulphides, owing to nucleophilic attack by sulphur at oxygen. An extension of work described in 1%9 by the same authors showing the ability of sulphides and thiols to quench pffioto-excited benzophenone has been described. ... 

Ariya, P.A. Sander, R. Cmtzen, P.J., 2000 Significance of HOx and Peroxides Production due to Alkene Ozonolysis During Fall and Winter A Modeling Study , in Journal of Geophysical Research, 105,D14 ... 

Formation of C5-C9 carboxyhc acids from alkene ozonolysis under dry and humid conditions, J. Phys. Chem. A, 109, 5366-5375. 

Now let s draw the forward scheme. The 3° alcohol is converted to 2-methylpropene using strong acid. Anti-Markovnikov addition of HBr (with peroxides) produces l-bromo-2-methylpropane. Subsequent reaction with sodium acetylide (produced from the 1° alcohol by dehydration, bromination and double elimation/deprotonation as shown) produces 4-methyl-1-pentyne. Deprotonation with sodium amide followed by reaction with 1-bromopentane (made from the 2° alcohol by tosylation, elimination and anfi -Markovnikov addition) yields 2-methyl-4-decyne. Reduction using sodium in liquid ammonia produces the E alkene. Ozonolysis followed by treatment with dimethylsulfide produces an equimolar ratio of the two products, 3-methylbutanal and hexanal. 

This strategy requires that we first convert the starting alcohol into the alkene above, which can be achieved by treating the alcohol with PBrs, giving an alkyl halide, followed by elimination with a strong, sterically hindered base (such as ferf-butoxide) to give an alkene. Ozonolysis of the alkene gives pentanal, which can be converted into the product via reductive amination, as shown ... 

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