1,3-Diketones, intramolecular oxidative

Dimerization of ketone enolates. Frazier and Harlow1 have noted that ketone enolates (LDA or KH) couple to 1,4-diketones when oxidized by dry FeCl3 in DMF. Yields range from 25 to 70%. Paquette et al.2 have extended this reaction to intramolecular coupling of a bisenolate to a cyclopropane. Thus addition of a... 

Cyclohexanediones. Paquette and co-workers have applied Saegusa s method (6, 139) to the intramolecular oxidative coupling of 1. Addition of the dicnolate obtained from 1 to a solution of anhydrous CUCI2 in THF and DMF at - 78° affords the polycyclic diketone 2 in 58% yield. 

Oxidative Coupling. Both intermolecular and intramolecular oxidative coupling reactions can be effected using Cu(OTf)2. Examples of dimerization include one-pot syntheses of 1,4-diketones from ketone enolates or from silyl enol ethers (eqs 1 and 2), and coupling of allylstannanes with TMS-enol ethers... 

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)." ... 

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

The configuration was assigned after oxidation of (43) and (44) to the corresponding 3,20-diketones. The diketone obtained from (44) showed an intramolecular bonded hydroxyl absorption at 3450 cm h Inspection of molecular models indicates that only a 12 -hydroxyl function can form an internal hydrogen bond to the 20-carbonyl group. 

There are also reactions in which electrophilic radicals react with relatively nucleophilic alkenes. These reactions are exemplified by a group of procedures in which a radical intermediate is formed by oxidation of readily enolizable compounds. This reaction was initially developed for /3-ketoacids,311 and the method has been extended to jS-diketones, malonic acids, and cyanoacetic acid.312 The radicals formed by the addition step are rapidly oxidized to cations, which give rise to the final product by intramolecular capture of a carboxylate group. 

A total synthesis of functionalized 8,14-seco steroids with five- and six-membered D rings has been developed (467). The synthesis is based on the transformation of (S)-carvone into a steroidal AB ring moiety with a side chain at C(9), which allows the creation of a nitrile oxide at this position. The nitrile oxides are coupled with cyclic enones or enol derivatives of 1,3-diketones, and reductive cleavage of the obtained cycloadducts give the desired products. The formation of a twelve-membered ring compound has been reported in the cycloaddition of one of the nitrile oxides with cyclopentenone and as the result of an intramolecular ene reaction, followed by retro-aldol reaction. 

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 aza-Wittig reaction of 1,3-diketones (134) and hydra-zinobis(iminophosphoranes) (133) gives pyrazole (135) on elimination of two equivalents of triphenylphosphane oxide, as shown in Scheme 53 (75CB623). 

Upon oxidation with IBD, a series of o-hydroxyacetophenones and related compounds 57 give the corresponding 2-methoxycoumaran-3-ones 59 [84JCS(CC)1342] (Scheme 19). These reactions probably occur via intramolecular participation of the ortho hydroxy group, which attacks the a-carbon of the intermediate 58 to yield the intermediate product 58a. A similar reaction occurs when /3-diketones 60 are oxidized with IBD-KOH/MeOH,... 

Although arylation or alkenylation of active methylene compounds can be carried out using a Cu catalyst, the reaction is sluggish. However, the arylation of malononitrile (390) or cyanoacetate proceeds smoothly in the presence of a base and Pd catalysts [189], Tetracyanoquinodimethane (392) is prepared by the coupling of / -diiodoben-zene with malononitrile (390) to give 391, followed by oxidation [190], Presence of the cyano group seems to be essential for intermolecular reactions. However, the intramolecular arylation of malonates, / -keto esters and /i-diketones proceeds smoothly [191]. The bromoxazole 393 reacts with phenylsulphonylacetonitrile (394)... 

Hydrolysis (the reverse of the preparative reaction) and other exchange reactions of the metal /3-diketonates have been studied in some detail in order to probe the mechanisms of inorganic substitution reactions. As mentioned in Section 4.1, there has been intense study of the intramolecular rearrangements of M(dike)3 complexes. Decomposition of metal /1-diketonate complexes to give high-purity metals or metal oxides is of technological importance. 

The intramolecular electron exchanges among the different metal sites of polynuclear /3-diketonate-metal complexes are a matter of intrinsic interest, especially as far as the stabilization of mixed-valent oxidation states is concerned " . Obviously, the pertinent electrochemical pattern, while becoming richer and richer, also tends to become more... 

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