1,3-Diketones, intramolecular oxidative cyclization

Examples of intramolecular oxidative cyclizations promoted by Cu(OTf)2 include cyclization of enolates of diketones and diesters (eq 4) and oxidative cyclization of hydrolytically resistant, s-and ,( -unsaturated silyl enol ethers." For instance, (1) reacts with excess Cu20/Cu(0Tf)2 in MeCN to give a 90% yield of a 20 1 mixture of the trans-fused and cis-fused tricyclic ketones (2) and OHeqS)." ... 

The ozonolysis of cyclobutene derivatives in the preparation of 1,4-diketones was also applied to the total synthesis of eyclopentanoid antibiotics 161 162k The oxidative cleavage of (470) by ozone and reductive work-up yielded the diketone (471) in 73 % yield. Diketone (471) underwent intramolecular aldol cyclization to give the key intermediate (472), which was used to synthesize ( )-xanthocidin161,162), (+)-epi-xanthocidin 162), ( )-p-isoxanthocidin161,162) as well as ( )-desdihydroxy-4,5-didehydroxanthocidin162). 

An intramolecular vinylogous amide photocycloaddition, retro-Mannich fragmentation and final Mannich cyclization cascade provided a useful method for the synthesis of the complex ABCE ring system [91], The preparation of the requisite photosubstrate is outlined in Scheme 28. After cluomatographic separation, the cis alcohol was irradiated and led to the formation of aminals in a 2 1 ratio. Equilibration studies of the Swem oxidation products revealed that exposure of the minor diketone to sodium methoxide in methanol effected conversion to the manzamine-unlike... 

Synthetic approaches to 1,5-benzodiazepines and related fused diazepines are frequently accomplished by condensing o-diamino>derivatives of aromatic rings with alkenones, alkynones, jff-diketones, /S-keto-esters, etc, or by intramolecular cyclization of appropriate derivatives of the u-diamino-compounds. Condensations with alkenones are exemplified this year by the reaction of the diamino-uracil (230) with mesityl oxide (or two moles of... 

As a further model compound for rigidified polythiophene, Roncali et al. have developed a new synthesis of the first fully planar terthiophene by bridging the internal /3-positions [203], The synthesis is based on the cyclic ketone 228 which is oxidatively dimerized after deprotonation by CuCl2 to the 1,4-diketone 229 (30% yield). Intramolecular cyclization of 229 with L.R. affords the rigid 4if,5/f-dicyclo-penta[2,l-b 3,4-b 2 l -a 3, 4 -b"]terthiophene 230 in 45% yield. 

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