Ozonides preparation

For reducing ozonides or sterically hindered peroxides, magnesium and methanol proved to be a better and mild reducing agent <2004JOC2851>. Thus, the bicylic ozonide prepared from 1-phenylcyclopentene, which is prone to base-mediated cleavage, was cleanly reduced by Mg/MeOH to the keto-acid with the ketonic methyl ester as a by-product, whereas reduction with zinc and acetic acid affords mainly the keto-aldehyde with the keto-acid as a by-product (Equation 7). 

Addition compounds called ozonides are produced when alkenes react with ozone and reductive cleavage of these compounds is used extensively in preparative and diagnostic organic chemistry. 

How would you obtain a sample of pure ozone Account for the conditions used in your method of preparation. What is the arrangement of oxygen atoms in an ozonide and what evidence would you cite in support of the structure you suggest ... 

The relevant properties of peroxide and superoxide salts are given in Table 4 (see Peroxides and peroxide compounds, inorganic). Potassium peroxide is difficult to prepare and lithium superoxide is very unstable. The ozonides, MO3, of the alkah metals contain a very high percentage of oxygen, but are only stable below room temperature (see Ozone). 

The unstable ammonium ozonide [12161 -20-5] NH O, prepared at low temperatures by reaction of ozone withHquid ammonia, decomposes rapidly at room temperature to NH NO, oxygen, and water (51). Tetrametbylammonium ozonide [78657-29-1] also has been prepared. 

The ozonides are characterized by the presence of the ozonide ion, O - They are generally produced by the reaction of the inorganic oxide and ozone (qv). Two reviews of ozonide chemistry are available (1,117). Sodium ozonide [12058-54-7] NaO potassium ozonide [12030-89-6] 35 rubidium ozonide [12060-04-7] RbO and cesium ozonide [12053-67-7] CsO, have all been reported (1). Ammonium ozonide [12161 -20-5] NH O, and tetramethylammonium ozonide [78657-29-1/, (CH ) NO, have been prepared at low temperatures (118). 

Other methods have been described to produce dodecanedioic acid. Cyclododecene is prepared from cyclododecatriene by partial hydrogenation. Ozonolysis of the cyclododecene followed by oxidation of the intermediate ozonides gives dodecanedioic acid (72). Hydrogenation of riciaoleic acid gives 12-hydroxystearic acid, which upon treatment with caustic at high temperatures, 325—330°C, gives a mixture of undecanedioic and dodecanedioic acids. 

Unusually stable ozonides are prepared by treating mono- and bisffluroal-kyl)ethylenes with ozone [26] (equation 17)... 

But their instability makes it difficult to prepare them in good yields and to use them safely in reactions. Ozonides or ozonolysis products have at times expld on standing. Ozonolysis products are also thermally unstable. One must maintain the reaction at a certain temp in order to prepare and react these compds. Moreover, since the ozone addition reaction is highly exothermic, reactors must be cooled to maintain the desired temp (Ref 4)... 

Few kinetic studies of the decompositions of higher oxides have been reported one probable reason is that the preparation of pure samples of these highly reactive compounds is difficult. Accordingly, interest has been largely restricted to the most readily available substances which are the alkali and alkaline earth peroxides (02-), superoxides (02) and ozonides (03). Some of these may be hydrated. E values reported [656] for the dehydrations of M02 8 H20 (288—313 K) were 96, 163 and 63 kJ mole-1 for the Ca, Sr and Ba compounds, respectively. 

It follows that tetrasubstituted alkenes do not normally give ozonides. However, they do give the normal cleavage products (ketones) by the other pathways. For the preparation of... 

Ozonoiysis is a reaction used with unsaturated hydrocarbons when preparing aldehydes and ketones, by reducing intermediate ozonide or acids by oxidation. The reducing agents used include hydrogen in the presence of palladium, and zinc in acid medium. 

A number of the bicyclic ozonides 12 were prepared in good yield (45-65 %) by diimide reduction of furan singlet oxygenates (Eq. 9) 23>. Again, low temperature were essential because the furan endoperoxides readily transform into 1,2-diacyl-ethylenes. Of course, the bicyclic ozonides 12 can alternatively be prepared via ozonolysis of the appropriate 1,2-disubstituted cyclobutene 24). 

The zwitterion (59) is thereby prevented from reacting with the ketone (58) to form the ozonide in the normal way, and both (58) and (60) may now be isolated and identified. In preparative ozonolysis it is important to decompose the ozonide (57a) by a suitable reductive process, as otherwise H202 is produced (on decomposition of the ozonide with H20, for example) which can further oxidise sensitive carbonyl compounds, e.g. aldehydes— carboxylic acids. 

The unusually stable cross-ozonide 89 has been reported <06TA1780>, and a range of isomeric mono- and disulfoxides of the E-cyclooctene-derived 1,2,3-trithiolane 90 have been prepared <06T5441>. 

The experimental procedure described is essentially one reported by Ziegler and Wilms 8 as subsequently modified,9 except that the glutaraldehyde is prepared from 2-ethoxy-3,4-dihydro-2H-pyran instead of cyclopentene ozonide 8 or pyridine via dihydropyridine and glutaraldehyde dioxime.9 Essentially these procedures have also been reported briefly by other investigators.10... 

Schaap, A.P., Siddiqui, S., Prasad, G., Palomino, E. and Sandison, M. (1985). The photochemical preparation of ozonides by electron-transfer photo-oxygenation of epoxides. Tetrahedron 41, 2229-2235... 

The preparation, properties and uses of ozonides have been reviewed comprehensively [1]. Many pure ozonides (trioxolanes) are generally stable to storage some may be distilled under reduced pressure. The presence of other peroxidic impurities is thought to cause the violently explosive decomposition often observed in this group [2], Use of ozone is not essential for their formation, as they are also produced by dehydration of c cF-dihydroxy peroxides [3], A very few isomeric linear trioxides (ROOOR) are known, they are also explosively unstable. Inorganic ozonides, salts of the radical C>3 anion, are also hazardous. 

Cyclic enones can be oxidatively cleaved by a range of reagents to yield keto acids. As ozonolysis can be quite hazardous for large-scale preparations with the build up of ozonides, the procedure has been modified using quaternary ammonium salts to catalyse the transfer of peroxide anion for a rapid oxidative work-up [32]. Two methods are available but, in the safer procedure (10.7.15.A), there is no effective build-up of the ozonide. 

Different isomers of C qO have been prepared by photooxygenation [48], by MCPBA-oxidation [48], by ozonolysis [49] or they were extracted from fullerene soot [11, 50]. Isolation from fullerene soot and analysis of the product of photooxygenation and thermal ozonolysis yields only [6,6]-closed epoxide structures. As already observed for CgoO, ozonolysis and subsequent photolysis of the ozonide C7QO3 gives different [5,6]-open oxidoannulene structures [49]. 

The double )5-scission pathway becomes dominant in bicyclic systems (Equations (7)-(9) and Scheme 13). Thus, cyclopentene ozonide (69) gives cyclopropane (Equation (7)) <68TL329l>. Photolysis of the ozonide derived from 1,4-benzodioxins (70) provides a method for the preparation of labile o-benzoquinones (71) (Scheme 13) <87JOC56l6>. Photolysis can also provide a route to unstable compounds and transient species such as the aziridine-2,3-dione (72) (Equation (8)), identified at 77 K using infrared spectroscopy <80JA6902>. Relatively unstable azacarbapenems (73) have been prepared by photolysis of tricyclic compounds containing a cyclobutene ozonide (Equation (9)). On silica, the 1,2,4-trithiolane (74) underwent photo-equilibration (Equation (10)) with the 1,3-dithetane (75) and sulfur. 

A 1989 report describes preparation of 3-alkoxy-l,2,4-trioxolanes (122) by reaction of the corresponding 3-acetoxy derivative (123) with an alcohol under basic conditions (Equation (22)) <89TLi5ii>. Apart from the unusual related reaction of diozonide (120) in Section 4.16.6.2, this sort of nucleophilic substitution at an ozonide is rare. 

The most commonly employed transformations for the construction of five-membered rings containing three sulfur or oxygen atoms in the 1,2,4-positions are shown in Table 11. These have attracted more interest than the syntheses from acyclic components. The rearrangement of a 1,2,3-trioxolane (primary ozonide) to a 1,2,4-trioxolane (secondary ozonide) is the most generally applicable method for preparation of this ring system and will be discussed further in Sections... 

---