Ketone utilization

The five-week laboratory is based on the report by Lattanzi that describes the asymmetric expoxidation of rmsaturated ketones utilizing (S)-a,a-... 

The N-anthracenylmethyl ammonium catalysts 11 and 12 also proved to be very effective in the asymmetric epoxidation of a,p-unsaturated ketones utilizing aqueous sodium165,661 or potassium1671 hypochlorite solution as an oxidant. Protection of the hydroxyl group in the N-anthracenylmethyl ammonium salts may be essential to attain high enanti-oselectivities in the epoxidation165"671, and use of... 

Next to TBHP also ferf-pentyl hydroperoxide, cumyl hydroperoxide and cyclohexyl hydroperoxide could be employed as oxidant and 2-hydroxycyclobutanone and 2-hydro xycyclododecanone were prepared by this method as well. In 1985, Vedejs and Larsen reported on a preparative method for the a-hydroxylation of camphor and a variety of other ketones utilizing overstoichiometric amounts of oxodiperoxomolybdenum(pyridine)(hexamethylphosphoric triamide) as source of oxygen (equation 67). Yields of products ranged from 34-81% and in some cases also the a-diketone is formed as by-product (0-26%). 

Table 6. Preparation of Unsymmetrical Ketones Utilizing Thexylchloroborane as Intermediate 73>...

Enzymes Involved In ketone utilization In different types of muscle adaptation to exercise. Eur. J. Blochem. 47 461-7. 

One of the oldest methods for effecting the a-hydroxylation of ketones utilizes transition metal salts, the most widely employed being lead tetraacetate (LTA). Treatment of enolizable ketones with LTA (usually at reflux in acetic acid or benzene) affords the corresponding a-acetoxy derivatives. Originally a radical mechanism was proposed (Scheme 1), but elsewhere it has been suggested that an incipient or-ganolead species is involved prior to conversion to the a-acetoxy derivative by inter- or intra-molecular nucleophilic attack (Scheme 2). 

A rapid, high-yielding procedure for the conversion of o-nitrobenzaldehydes to quinolines (a modification of the Friedlander synthesis) has been reported <03OL4257>. The method appears to be limited in that the ketones utilized must be symmetrical. An example is shown below. 

The most suitable technique for addition of aromatic aldehydes to a,3-unsaturated ketones utilizes cyanide catalysis in DMF (equation 2). Unsubstituted aromatic aldehydes and those bearing substituents in the ring, except for ort/io-substituted benzaldehydes, can add to an aliphatic, aromatic or heterocyclic a,3-unsaturated ketone. Addition of heterocyclic aldehydes can be catalyzed by cyanide ion as well. The... 

Sano, S., Takehisa, T., Ogawa, S., Yokoyama, K., Nagao, Y. Stereoselective synthesis of tetrasubstituted (Z)-alkenes from aryl alkyl ketones utilizing the Horner-Wadsworth-Emmons reaction. Chem. Pharm. Bull. 2002, 50, 1300-1302. 

ADDITION TO CHAPTER XV Following the epimerization (at C-14) of l-bromo-/ -thebainone-A 2 4-dinitrophenylhydrazone to 1-bromothebainone-A 2 4-dinitrophenylhydra-zone [3] (see Chap. XXVIII), it has been shown that in acetic acid or sodium ethoxide solution / -thebainone-A is converted into an equilibrium mixture of /3-thebainone-A and thebainone-A [xxi], the equilibrium favouring the latter ketone. Utilizing this reaction a method has been developed for the preparation of thebainone-A in good yield from dihydrothebaine- [xxn] [4]. 

Hata, T, Hashizume, A., Nakajima, M., and Sekine, M., a-Hydroxybenzyl anion equivalent. A convenient method for the synthesis of a-hydroxy ketones utilizing a-(trimethylsilyloxy)benzylphos-phonate, Chem. Lett., 519, 1979. 

For additions to ketones utilizing stoichiometric Sn diamine complexes, see Kobayashi S, Hachiya 1 (1992) J Org Chem 57 1324... 

Several structural modifications of the C-9 ketone of erythromycin have been explored oximes and hydrazones are less prone to intramolecular cydization, but they often have less antibiotic activity than erythromycin (140). Synthesis of more complex oxime derivatives resulted in the development of roxithromycin, the 9-[0-(2-methoxyethoxy)methyl]oxime (33) (141). Reduction of the oximes and hydrazones produced 9(S)-erythromycylamine (34) as the principal product, with minor amounts of the 9(R)-isomer (140) however, clinical studies showed that 9(5)-erythromycyclamine and its N-benzylidene derivative were poody absorbed in humans (142). Evaluation of more complex oxazine derivatives of erythromycylamine led to dirithromycin, the 2-(2-methoxyethoxy)ethylidene oxazine derivative (35) (143). A third route to modification of the ketone utilized a Beckmann rearrangement of the 9-oxime to expand the 14-membered ring to a 15-membered intermediate, which was subsequently reduced and AT-methylated to yield azithromycin (36) (144,145). The term azalide was proposed to denote these 15-membered azalactones (10,145). 

Scheme 8.30. Asymmetric nitrogen ring-expansion reactions of ketones utilizing...

From these results, it can be concluded that the mild conditions and nickel catalyst have resulted in a wider tolerance of functional groups and a greater scope of the reactions. Significantly, this strategy affords a more economically and environmentally useful and valuable synthetic procedure for the preparation of ketones utilizing organozinc reagents, which are readily available. 

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