Arenes ozonolysis

A stable ozonide of an arene. Ozonolysis of the cyclopentophenanthrene 1 leads to an ozonide (2) that is stable in the dark at 20° for several weeks. The ozonide is also unusual in that it is converted into 3 and 4 in high yield products of this type are not usually formed from ozonides. 

Exposed multiple bonds of angular arenes are specifically prone to oxidation. The synthetic value of such double bonds arises from their high reactivity towards simple electrophiles, enophiles, and radicals. Heavy metal catalysis, periodate oxidation, and ozonolysis are the standard tools for oxidative bond cleavage in these substrates. For economic and ecological reasons, technically applicable alternatives are of great interest. Phenanthrene (29) represents a typical substrate... 

Lithiated allyl sulfide 256-Li reacted with m-xylylene dibromide 257 to afford the bis-sulfide 258. A double Mislow-Evans rearrangement of 258 and subsequent reductive trapping of the sulfenate ester provided the symmetric trans-diol 255. Monoprotection, Sharpless asymmetric epoxidation, and reductive ring-opening of the epoxide gave 1,3-diol 259 in 97% ee. After several functionalizations, the arene was subjected to Birch reduction to provide 1,4-cyclohexadiene 254. Ozonolysis of the diene, followed by reductive workup and treatment of the resulting 1,3-diketone with acid furnished pyra-... 

When the aldehyde or ketone is being named as a substituent, the term "oxo" is used. Aldehydes can be prepared by oxidation of primary alcohols, hydroboration of 1-alkynes, or ozonolysis of alkenes. Aryl aldehydes can be prepared from the arene with CO/HCI in the presence of AlClj/CuCI. 

Synthesis of Arene Oxides. Reaction of (Me2N)3P with aromatic dialdehydes provides arene oxides such as benz[a]anthracene 5,6-oxide (2a) (eq 5). These compounds, also known as oxiranes, are relatively reactive, undergoing thermal and acid-catalyzed rearrangement to phenols and facile hydrolysis to dihydrodiols. Consequently, their preparation and purification requires mild reagents and condition.s. The importance of this is underlined by successful synthesis of the reactive arene oxide (2b) in 75% yield using appropriate care, despite a previous report of failure of the method. While compound (2b) is a relatively potent mutagen, it is rapidly detoxified by mammalian cells. The principal limitation of the method is the unavailability of the dialdehyde precursors, which are obtained through oxidation of the parent hydrocarbons, e.g. by ozonolysis. 

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