Criegee type rearrangement

A mechanism for extradiol cleavage is proposed in Figure 18 [5,158], Substrate binds first to the iron(II) center, followed by 02, to form a ternary complex akin to the ES—NO complex described earlier. Electron transfer from metal to 02 in the Fe(II)—02 adduct results in a superoxide-like moiety and imparts nucleophilic character to the bound 02. This in turn generates semiquinone character on the bound substrate, which is attacked by the nascent superoxide to form a peroxy intermediate that decomposes by a Criegee-type rearrangement to the observed product. 

The isomeric salts 126 are valuable starting compounds for the synthesis of bicyclic 3-hydroperoxides 267, which surprisingly reacted in heated H202 in acetic acid, to i s o t h i az o 1 - 3 (2 //) - o ne 1,1-dioxides 268a-d by a Criegee-type rearrangement (00JPR675, Scheme 90). 

In connection with the postulated mechanism for DNA strand scission by activated bleomycin, the hydroperoxide (68) was produced as the major isomer as shown in Scheme 19. In aqueous buffer, this underwent a Criegee-type rearrangement to give ultimately the unsaturated aldehyde (69). On reduction with dimethylsulphide, (68) gave... 

An alternative mechanism involves nucleophilic attack of the C-3 of indole on the distal oxygen atom of the bound O2 coupled with deprotonation. Two pathways to the Al-formylkynureiune product have been proposed, one involves a Criegee rearrangement-type mechaiusm and the other involves an endoperoxide intermediate Further studies are required to estabhsh the exact mechaiusm of product formation. 

The proposed mechanism of flavin-type Baeyer-Villiger MOs is shown. First reduction of the flavin 95 and attack on O2 provides 96. Peroxo-flavin 96 attacks ketone 93 and forms the Criegee adduct 97. Rearrangement provides lactone 94 along with hydroxylated flavin 98. Dehydration returns to the beginning of the catalytic cycle. 

An example of the rearrangement of an olefin [type ( )] was described by Criegee and Riebel 142 in a two-fold Wagner-Meerwein rearrangement,... 

In many papers, this intermediate is called an azonide in analogy to the similar type of compounds discovered by Criegee (see Criegee and SchrOder, 1960, and Criegee s review, 1975) in the ozonolysis of alkenes. In that reaction a 1,2,3-trioxolane, i.e., an ozonide, is initially formed which, however, rearranges via a carbonyl oxide of type 9.71 and a carbonyl compound into a 1,2,4-trioxolane like 9.77 (see review of Kuczkowski, 1983). 

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