Benzoyloximes

Isoxazole derivatives are stable toward peracids but can be ozonolyzed. This, as is well known, enabled the 0-benzoyloximes of a-diketones with a well established configuration to be obtained, which were used to investigate the Beckmann rearrangement mech-anism. ... 

Narasaka efal. have extended these crochet-mode cascade cyclizations to di- and trienyl-substituted o-pentafluoro-benzoyloximes 136 and 140, to furnish spirofused cyclic imines 139 and 141, respectively (Scheme 36)/" The latter structure has been found in some bioactive natural products such as cephalotaxine. 

When treated with benzoic acid in the presence of triphenylphosphine and diethyl azodicarboxylate, benzophenone oxime gave a high yield of f -benzoylbenzanilide (14), formed via rearrangement of the intermediate 0>benzoyloxime (15). Reaction of p>medioxyaGetophenone oxime with l,rsubstituted derivative (l ), whereas in the presence of allyl bromide... 

All the members of this class of compounds contain an aromatic ketone group, the most representative systems being benzoin [71], benzoin ethers [72], dialkoxy-acetophenones [73], hydroxyalkylphenones [74], benzoyloxime esters [75] and, more recently, benzoylphosphine oxides [76], a-hydroxymethylbenzoin sulfonic esters [77], sulfonyl ketones [78] and morpholino ketones [70],... 

Treatment of hydrazonium salt 4 with palladium(0) led to the formation of p3UTole 5 via 5-exo-trig amino-Heck cyclization <05H(65)273>. The reaction presumably proceeds by the oxidative addition of palladium(O) into an A-Abond. An oxidative addition into the A-O bond of benzoyloximes was the key step in the 5-endo-trig amino-Heck cyclization leading to 5-fluoro-3A-pyrroles <05CC4684>. 

Ketoxime esters of benzoin, exemplified by 1-phenyl-l,2-propanedione-2-0-benzoyloxime (PPO) (XXXI), on photolysis eliminate two volatile fragments after the primary scission of the N—O bond (Scheme 6.36). The radical yield of PPO decomposition is very high (9 0.9). The phenyl radical, the final product... 

Cyclobutylidene derivatives have been regio- and stereoselec-tively reduced to substituted vinyl cyclobutanes with Pd(dba)2 and sodium formate. Heteroaryl benzylic acetates (including 2° acetates) undergo Pd-catalyzed benzylic nucleophilic substitution with malonate nucleophiles. Cyclobutanone O-benzoyloximes have been converted to a variety of nitrile derivatives using Pd(dba)2 in combination with chelating phosphines (eq 27). ... 

Pyridines and quinolines are similarly prepared. The pyrrole 474 was obtained by 5-exo cyclization of 3-methoxy-l-phenyl-4-penten-l-one ( )-0-pentarfluoro-benzoyloxime 473 under usual conditions. On the other hand, 2-phenylpyridine (475) was obtained by 6-endo cyclization as the main product in the presence of n-Bu4NCl. Isoquinoline 477 was prepared in 77 % yield by 6-exo cyclization of the oxime 476 [179]. 

Benzoquinone. See Quinone Hydroquinone p-Benzoquinone. See Quinone Hydroquinone p-Benzoquinone bis (o-benzoyloxime). See Dibenzoyl-p-quinone dioxime... 

The preparation of the O-benzoyloxime derivative of 2,3,6-tri-O-benzoyl a-D-arflhino-hex-2-ulopyranosyl txomide and its teacdons with nucleophiles at the anomeric centre are covered in Chapter 8. 

Palladium-catalyzed reaction of cyclobutanone 0-benzoyloximes proceeded via oxidative addition of the N-O bond of the oxime to Pd(0) and P-carbon elimination of the resulting cyclobutylideneamidopalladium(II), affording a reactive alkylpalladium(II) species [48]. The a,P-unsaturated nitrile 64 was obtained when 3-phenylcyclobutanone 0-benzoyloxime (65) was reacted in the presence of a Pd(0)-BINAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) catalyst (Scheme 3.37). 

Scheme 3.37 Pd(0)-catalyzed ring opening of cyclobutanone 0-benzoyloxime 65.

Under similar conditions, O-benzoyloxime of 3,3-disubstituted cyclobutanone 66 formed cyclopropanecarbonitrile 67 (Scheme 3.38). The reaction proceeded via a pathway analogous to that proposed for ring contraction of 1,3,3-trisubstituted cyclobutanols. 

Scheme 3.38 Pd(0)-catalyzed ring contraction of cyclobutanone O-benzoyloxime 66.

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