Oximes oxime acetate

In a synthesis of sativene a carbonyl group was protected as a 2,4-DNP while a double bond was hydrated with BH3/H202/0H . Attempted protection of the carbonyl group as a ketal caused migration of the double bond protection as an oxime or oxime acetate was unsatisfactory since they would be reduced with BH3. 

Forms yellow plates from AcOH, and needles from EtOH [Slotta and Szyszke Chem Ber 68 184 7955]. With diazomethane,. 5-nitro-3,4-dimethoxyacetophenone is formed [Brady and Manjunath J Chem Soc 125 1067 1924]. The methyl ether crystallises from EtOAc or AcOH, m 88", 90-91", and the phenylhydrazone has m 108-110° (from aqueous EtOH). [Finger and Schott 7 C/icm [2] 115 288 7927.] Vor oxime m 216° (from EtOH or AcOH) and the oxime acetate has m 147° (from aq EtOH) [Vogel Monatsh Chem 20 384 1899 Brady and Dunn J Chem Soc 107 1861 7975]. 

Hydroxypregna-5,16-dien-20-one Acetate Oxime 3j5-Hydroxy-pregna-5,16-dien-20-one acetate (30 g) is dissolved in 300 ml of anhydrous pyridine and 6.75 g of hydroxylamine hydrochloride is added. The mixture is stirred until solution is achieved, left in a tightly closed container at room temperature for 4 days and then poured into 1.5 liters of water. The flask is rinsed with water and the combined separated crystals are collected on a Buchner funnel, washed with water and dried to constant weight in an oven at 100°. Yield 30 g (96.5% of theory) mp 220-223°. 

Hydroxypregna-5,16-dien-20-one, 134 3 -Hydroxypregna-5,16-dien-20-one acetate, 36, 196, 348, 349 3 -Hydroxypregna-5,16-dien-20-one acetate 20-ethyIene ketal, 210 3 -Hydroxypregna-5,16-dien-20-one acetate oxime, 143 3 -Hy droxy-5a-pregnan-20-one, 192 3p-Hydroxy-5a-pregnan-20-one 3-acetate, 264... 

Dibenz[c 1c ]azepine (32 a) is obtained by acid-mediated cyclization of 2 -(aminomethyl)bi-phenyl-2-carbaldehyde (31 a), which is generated in situ by reduction of the oxime acetal 30a.85 The acetyl 30 a and benzoyl 30c oximes behave similarly and give the dimethyl and diphenyl derivative 32 b and 32 c, respectively. 

Fermenting baker s yeast transformed 2-butanone oxime containing 44% excess of the ( )-isomer into optically active (R)-2-aminobutane in 58% enantiomeric excess. The chiral amine was also obtained in 24% e.e. from the oxime acetate but the oxime methyl ether gave a racemic product (equation 2)16. 

The synthesis of compounds 39, 41, and 43 by the ODPM rearrangement opens a novel photochemical route to chrysanthemic acid and other cyclopropane carboxylic acids present in pyrethrins and pyrethroids [52]. In fact, aldehyde 43 can be transformed to tran -chrysanthemic acid by simple oxidation. This new synthetic route to ecologically benign insecticides competes with the one previously described by us using the 1-ADPM rearrangement of p,y-unsaturated oxime acetates [30,53]. 

The DCA-sensitized irradiation of 107a for 13 hr affords, after column chromatography on silica gel, the rrans -cyclopropane derivative 108a (10%) as a 1 1 mixture of C=N bond fiZ-isomers. Similarly, irradiation of the oxime acetate 107b under these conditions for 2.5 hr affords, after chromatography, the rrans -cyclopropane derivative 108b (12%). These results show that the novel 1-ADPM rearrangement promoted by electron-transfer sensitization can be extended to other C—double-bond derivatives. 

In qualitative terms, the rearrangement reaction is considerably more efficient for the oxime acetate 107b than for the oxime ether 107a. As a result, the photochemical reactivity of the oxime acetates 109 and 110 was probed. Irradiation of 109 for 3 hr, under the same conditions used for 107, affords the cyclopropane 111 (25%) as a 1 2 mixture of Z.E isomers. Likewise, DCA-sensitized irradiation of 110 for 1 hr yields the cyclopropane derivative 112 (16%) and the dihydroisoxazole 113 (18%). It is unclear at this point how 113 arises in the SET-sensitized reaction of 110. However, this cyclization process is similar to that observed in our studies of the DCA-sensitized reaction of the 7,8-unsaturated oximes 114, which affords the 5,6-dihydro-4//-l,2-oxazines 115 [68]. A possible mechanism to justify the formation of 113 could involve intramolecular electrophilic addition to the alkene unit in 116 of the oxygen from the oxime localized radical-cation, followed by transfer of an acyl cation to any of the radical-anions present in the reaction medium. 

Surprisingly, 3-(2-dialkylaminoethyl)-l,2-benzisoxazoles 207 can be easily obtained by direct cyclization of the corresponding Mannich bases oxime acetates 206 in refluxing benzene in the presence of anhydrous K2CO3 (equation 90). The known methods for ring closure to 1,2-benzisoxazole were ineffective for this class of pharmacologically relevant compounds . 

The oxime acetate (217) readily undergoes electrocyclization to the dihydropyridine (218), from which pyridine is derived by loss of acetic acid. 

Glyoidonrcrile itself has not been prepared directly from acrylonitrile, but was eyatheaized recently1311 from glycidaldehyde by pyrolysis of the corresponding oxime acetate, as shown in Eq, (67). 

Compounds 142 and 143 could be transformed into a variety of derivatives, such as acetals, oximes, semicarbazones, and hydrazones.154 Other types of monoketone-derived products, especially oxime ethers 144 containing a 3-amino-2-(hydroxypropyl) side-chain, have been synthesized and evaluated as potential drugs216 (see Scheme 39). 

NX - 5-alpha-ANOROSTAN-3-ONE, 17-beta-HYDROXY-, 0-(p-NITRQPHENYL)OXIME, ACETATE (ester ... 

To a solution of 1 gram of 16-dehydropregnenolon-3p-acetate in 10 ml pyridine is added 0.22 gram of hydroxylamine hydrochloride, and the mixture is allowed to stand at room temperature for four days. One gram of 16-dehydropregnenolon-3p-acetate oxime is dissolved in 30 ml of hot dioxane, and then the solution is cooled in an ice bath until about one-half of the dioxane has solidified. Then 1 gram of phosphorus pentachloride is added and the mixture is shaken until all the dioxane has melted. The mixture is maintained at 35°C, for seventy-five minutes, then an excess of ice is added and the solution is again allowed to stand at 35°C. After about thirty minutes, a solution of 5 ml of concentrated hydrochloric acid in 10 ml of water is added, and the mixture is diluted with water, extracted with ether and the ethereal extract washed with dilute sodium hydroxide solution. The ether is removed on a steam bath and the residue is worked up to yield dehydro-isoandrosterone. 

Among the numerous applications of this reaction reported over four decades, some typical examples of the functionalization are outlined in Schemes 3 to 10. Thus, Scheme 3 outlines the well-known Barton transformation of corticosterone acetate nitrite into aldosterone acetate oxime which, with nitrous acid, gives aldosterone 12-acetate [4]. The yield of 18-oxime is, however, rather low (21 %), since attack by the 11/3-alkoxyl radical on C-19 competes with the desired attack on C-18. Incorporation of the 1,2-double bond into the nitrite prevented undesired C-19 attack by the radical and a far better yield (47 %) of 18-oxime was achieved [5] (Scheme 4). This example may indicate that the Barton reaction is sensitive to... 

Pyrans-4-ones and their monobenzo derivatives are easily attacked by nucleophiles via 1,4-conjugate additions which result in subsequent ring opening. Reactivity of this type makes it difficult to convert the carbonyl groups to acetals, oximes, and hydrazones by conventional methods. Since their reactivity toward nucleophiles provides a useful route for the preparation of a variety of rearranged products and new heterocyclic systems, their versatility as reactive intermediates is well documented. 

Steric and electronic effects on the photochemical reactivity of oxime acetates of p/y-unsaturated aldehydes. Journal of the Chemical Society, Perkin Transactions 1, 163-169 (b) Armesto, D., Horspool, W.M., Mancheno, M.J., and Ortiz, M.J. (1990) The aza-di-jt-methane rearrangement of stable derivatives of 2,2-dimethyl-4,4-diphenylbut-3-enal. Journal of the Chemical Society, Perkin Transactions... 

Acetophenone-sensitized photolysis of l-methyl-3-phenyl-2-cyclohexene-carbaldehyde oxime acetate (56) A solution of 56 (298 mg, 1.16 mmol)... 

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