0-Allyl oximes

It has been shown that phenylselenyl halides easily reacted with 0-allyl oximes 221 to give cyclic iminium salts 222, which by reaction with water afforded isoxazolidines 223 in moderate to good yields (equation 96) . Compounds 222 can be reduced in situ by sodium borohydride to produce Ai-alkyl-substituted isoxazolidines 224 in 50-95% yields . ... 

As reported in CHEC-II(1996) <1996CHEC-II(7)921>, compounds with a central seven- or eight-membered ring can be prepared by cyclization of an 0-allyl oxime. However, only one report in this area could be found, the full paper by Wang and Wong on their previously described synthesis of 108 <1995T6941>. 

Only one method for the synthesis of these types of compounds has been reported through the thermal cyclization of 0-allyl oximes in moderate to good yield (see, for example, <1995TL6941>). 

Compounds with central seven- and eight-membered rings (52 n = 3 or 4) are formed by the thermal cyclization of the 0-allyl oximes (109) <87IC2370>. 

Dihydro- E7b/2,353 [Cyclopenta-non-(0-allyl-oxim)/ A], 469 (1,2,3-Triazin + 1-NR2 -cyclopen-ten), 483 (1,2,4-Triazin + Cyclo-pentanon)... 

The same methodology was employed by Tiecco to effect the cyclizations of 0-allyl oximes 164 indicated in Scheme 25. Treatment of the intermediate iminium salt 165 with sodium borohydride affords M-alkyl isoxazolidines 166 [95]. Alternatively, 165 can be treated with water to produce M-unsubstituted isoxazolidines 167 [96]. This synthesis of M-alkyl isoxazolidines represents a valid alternative to that described in Scheme 23. Moreover, the present cyclization reaction is much more stereoselective than the cyclization of 0-allyl hydro-xylamines. In fact, when the methyl derivative 168 was employed, the two isomeric isoxazolidines 153 and 154 were obtained in a ratio of 95 5. The same two products were, in contrast, formed in a 1 1 ratio when the reaction was carried out starting from the corresponding 0-allyl hydroxylamines. Clearly, the steric requirements for the selenium-induced cyclization of the 0-allyl oximes are much greater than those for the corresponding 0-allyl hydroxylamines. 

Optically active isoxazolidines were prepared by 4b-cyclization of 0-allyl oximes induced by enantiopure selenylat-ing agents (Scheme 121) <2001TA3053>. 

The regioselective synthesis of pyrroles via [3,3]- and [l,3]-sigmatropic rearrangements of 0-vinyl oximes formed by iridium-catalysed isomerization of 0-allyl oximes is such that when enolization is favoured, a [3,3]-rearrangement followed by a Paal-Knorr cyclization gives a 2,3,4-trisubstituted pyrrole and when enolization is disfavoured, a [l,3]-rearrangement occurs prior to enolization to give a 2,3,5-trisubstituted pyrrole after cyclization (Scheme 10). ... 

Isoxazolidines by Cyclization of O-Allyl Oximes and O-Allyl Hydroxylamines... 

The cyclization of O-allyl oximes 1, performed with diphenyl diselenide/ammonium thiosulfate/ trifluorosulfonic acid or phenylselenenyl bromide, gave cyclic iminium salts 2 via an intramolecular antt -addition mechanism. By addition of water to the reaction mixture, 3-substi-tuted isoxazolidines 3 are formed in good yield. When the salts 2 were prepared by using phenylselenenyl bromide, A-alkyl 3-substituted isoxazolidines 4 were afforded in good yield by reduction of 2 with sodium borohydride in methanol247-249. 

The O-allyl oxime (302), prepared from 2,6-dimethyl-4-propionyl-4//-l,2,6-thiadiazine-3,5 (2//,6//)-dione 1,1-dioxide (Section 6.16.6.3.2) has pronounced herbicidal activity <89BRP22I3145>. 

The asymmetric endo cyclisation reactions of various substituted O-allyl oximes 110, promoted by the enantiomcrically pure sclenyl trillatc 111, afforded optically active isoxazolidines 112 in high yields (58-93%) and with good diastcreoselectivity (up to 93 7). The organoselenium moiety could be then removed by treatment with Ph. SnH in the presence of a catalytic amount of AIBN <01TA.3053>. 

O-Allyl oxime carbonates -, C-allylation with - 43, 723 Allyloxy-2-acetylenes... 

The anions of malonate esters, cyclopentadiene, -keto esters, ketones, " aldehydes, a-nitroacetate esters, Meldrum s acid, diethylaminophosphonate Schiff bases, -diketones, -sulfonyl ketones and esters, and polyketides represent the wide variety of carbon nucleophiles effective in this reaction. Generation of the stabilized anions normally is accomplished by addition of sodium hydride, potassium hydride, or basic alumina. However, when allyl substrates such as allylisoureas, allyl oxime carbonates, or allyl imidates are used, the allylation reaction proceeds... 

Interestingly, the non-catalytic thermolysis of O-allyl oxime leads mainly to quinoline (when conducted on air) or isoxazolidines composed of two molecules of the starting O-allyl ketoximes (under argon) as depicted later on example of O-allyl cyclohexanone oxime (Scheme 1.140) [318],... 

A method for protecting ketones and aldehydes is the formation of oximes, but sometimes further protection of the oximes is required. For this purpose, the oximes can be protected as allyl ethers. The oxime ethers ean be eleaved with triethylammonium formate in boiling dioxane[444]. The allyl ether of oximes is eleaved under mild conditions without attaeking the aeetal group in 677. 

Oxidation, allylic, 56,25 of alcohols, 55, 84 58,122 Oxime ( -allyl ethers, 58,10 S y-(2-Oxobut-3-yl)butanethioate, 55, 129 4-Oxocarboxylic acid esters, 58, 81 S-substituted, 58, 82... 

Chiral tricyclic fused pyrrolidines 29a-c and piperidines 29d-g have been synthesized starting from L-serine, L-threonine, and L-cysteine taking advantage of the INOC strategy (Scheme 4) [19]. L-Serine (23 a) and L-threonine (23 b) were protected as stable oxazolidin-2-ones 24a and 24b, respectively. Analogously, L-cysteine 23 c was converted to thiazolidin-2-one 24 c. Subsequent N-allylation or homoallylation, DIBALH reduction, and oximation afforded the ene-oximes, 27a-g. Conversion of ene-oximes 27a-g to the desired key intermediates, nitrile oxides 28 a-g, provided the isoxazolines 29 a-g. While fused pyrrolidines 29a-c were formed in poor yield (due to dimerization of nitrile oxides) and with moderate stereoselectivity (as a mixture of cis (major) and trans (minor) isomers), corresponding piperidines 29d-g were formed in good yield and excellent stereoselectivity (as exclusively trans isomers, see Table 3). 

The unsaturated oximes 224 (see Table 21) were readily prepared by AT-alkyl-ation of allyl amines with a-bromoketones or O-silyl-a-bromoaldoximes. Heating the oximes 224 in toluene under an argon atm at 110 -180 °C smoothly led to isoxazolidines 225 in good yields with cis ring junction stereochemistry. Even when three stereocenters were generated, as in 225 g-1, a single stereoisomer... 

Answer This branched primary amine can be made from ketone (21) via the oxime (p T 63). A 1,2 C-C disconnection on (21) is good as it needs the symmetrical allylic halide (22). 

Indium-mediated allylation reactions of a-keto imides derived from Oppolzer s sultam proceeded in aqueous THF in good yields and excellent diastereoselectivity (Eq. 11.43).74 The indium-mediated allylation of the Oppolzer camphorsultam derivatives of glyoxylic oxime ether... 

See Other ALLYL COMPOUNDS, NITROARYL compounds, oximes... 

Oxidation of (alkenylthio)thiophenecarboxaldehyde oxime 350 (R = allyl) by NaOCl gives the nitrile oxide, which cyclizes to thieno[2,3-h]thiocino[4,5-c] isoxazole 351. However, isomeric 350 (R = isopropenyl), under the same conditions, is converted to the unusual product, thieno 2,3-/ thiocin 352. In both reactions, cyclodimerization products of nitrile oxides are also obtained. Structures of compounds 350 (R = isopropenyl) and 352 have been studied by X-ray diffraction analysis (411). 

Selective formation of nitrones can be achieved using Pd (II) [Pd(cod)Cl2] as a catalyst, in the reaction of oximes with allylic acetate (Scheme 2.49) (303). 

Oximes are also good substrates for allylsamarium bromide addition.25 The Beckmann rearrangement product 44 was produced from oxime 43 in good yields when the ratio of allysamarium bromide to oximes was more than 3 1 (Equation (8)). This type of product was also obtained when the other allylic organometallic compounds were used. The reaction mechanism was proposed as shown in Scheme 13. 

Kondo and Watanabe developed allylations of various types of aldehydes and oximes by using nucleophilic (7r-allyl)ruthenium(ll) complexes of type 154 bearing carbon monoxide ligands (Equation (29)).345 These 73-allyl-ruthenium complexes 154 are ambiphilic reagents and the presence of the carbon monoxide ligands proved to be essential to achieve catalytic allylation reactions. Interestingly, these transformations occur with complete regioselectivity only the more substituted allylic terminus adds to the aldehyde. 

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