O-Dialdehydes

Diazocine structures at various oxidation levels have been attributed on numerous occasions to condensation products of o- dialdehydes, o-acylbenzoic acids or (3-aroylpropionic acids with 1,2-diamines, but the compounds have later been shown to be imidazoisoindole derivatives (217) (74JHC89, 72BSF2868,67JOC2180, 67JOC2185). 

Scheme 5.16. Formation of a series of hydrolytically stable dipyranoid disaccharide mimetics from homologous dihydroxy-a,o)-dialdehydes by tandem enzymatic aldolizations. Major diastere-omers are shown. Reaction conditions include sequential treatment by aldolase and phosphatase.

Ozonolysis of a cyclic alkene leads to oxidative cleavage, but the two carbonyl fragments are connected, so there is only one product rather than the two observed from ozonolysis of 2,3-dimethyl-2-butene or 2-methyl-2-pentene. When cycloheptene, for example, is treated with ozone and then with zinc and acetic acid, oxidative cleavage leads to the a,(o-dialdehyde 146 (1,7-heptanedial or 1,7-heptanedicarboxaldehyde). 

The multicomponent reaction of o-dialdehydes with two molecules of cyclic 1,3-dicarbonyls in acetic acid involves a stereoselective [4 + 1]/[3+ 2 + 1] biscydizations to give indeno-fused xanthenes (Scheme 82) (13TL6341). 

Ring closure with o-dialdehydes Condensed p-quinones... 

Abnormal imidazolylidene ruthenium complex 45 was developed by Bera and co orkers for the NaI04-mediated oxidation of olefins as a mild alternative to ozonolysis [eqn (3.9)]. For example, styrene was oxidized to benzaldehyde quantitatively in half an hour at room temperature with only 1 mol% 45. Internal olefins were oxidized very efficiendy as well, and cyclic olefins such as cyclohexene afforded a,o)-dialdehydes in excellent yields. Traces of over-oxidation to the corresponding carboxylic acids were only observed with aliphatic olefins. Also,... 

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