Communications - Preparation of Oxaziranes by Irradiation of Nitrones

Splitter, Janet S.; Calvin, Melvin

doi:10.1021/jo01098a635

Cited by 105 publications

(32 citation statements)

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“…wich corroborates previous observations [S], suggesting either a protonation at some step or the formation of the intermediate oxaziridine proceeding via a polarized excited state [9]; 3) use of thin irradiation layers (-1 cni), suggesting a possible wail effectz). These conditions were applied to the testosterone oximes (5 and 6) [lo] and to those of 17P-acetoxy-androsta-4,6-dien-3-one (9 and lo), obtained from the corresponding ketones 4 and 8, respectively ; in each case the geometrical isomers were separated by column chromatography3).…”

Section: L)supporting

confidence: 91%

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

Armengol

Coll

Reixach

et al. 1976

Helvetica Chimica Acta

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Sumnzary. The carefully controlled UV. irradiation of 3-hydroxyimino-d4-and 3-hydroxyimino-A4,A6-steroids yield as a result of vinyl and alkyl migration, lactams besides products expected.Rearrangement of conjugated steroidal ketonic nitrones yields N-substituted lactams as a result of vinyl migration (1 -+ 2) [Z]. Synthesis of the analogous N-nonsubstituted compounds 3 seems not to be feasible: The Beckmann rearrangement of the appropiate oximes gives only the alkyl migration isomers (e.g. 5 and 6 + 7) [3], and by irradiation 5 and 6 or similar unsaturated oximes show either a remarkable lack of reactivity [4], or syn-anti isomerization and fragmentation to ketone, followed by a slow and extensive decomposition [4] [5]. In no case have the least mentioned authors reported the formation of lactams as a result of a photo-Beckmann rearrangement. Nevertheless, from our previous work, a) the isolation of a lactam after UV. irradiation of 3-hydroxyimino-17~-acetoxy-androsta-l, 5-diene [6], and b) the photolability of conjugated lactams to give mainly dimers [7], suggest that the photoBeckmann rearrangement of 5 or 6 and of analogous oximes may take place, the primarily formed lactamic products not being detected owing to their further photochemical reaction.A systematic study was therefore undertaken and the following were found to be the most suitable conditions for photo-rearrangement : 1) Use of a medium pressure Hg lamp without filter, short irradiation time (-30 min), and low concentration (-O.lyo) ensure that the photo-Beckmann rearrangement takes place quickly, and secondary reactions (dimerization) are minimized; 2) use of a hydroxylic solvent, l)For part V, see [l].

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Section: L)supporting

confidence: 91%

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

Armengol

Coll

Reixach

et al. 1976

Helvetica Chimica Acta

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“…Photochemical rearrangements of nitrone to oxaziridine,5 and oxaziridine to amide6 have been individually documented starting in the 1950s. However, there are only sporadic reports of a one‐pot photochemical rearrangement of nitrones to amides,7 and to the best of our knowledge, no peptide bond formation using this approach has been described 8.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Study on the Mechanism of Ni‐Catalyzed Alkyl–Alkyl Suzuki Cross‐Coupling

Jiang

2012

Chemistry A European J

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Ni-catalyzed cross-coupling of unactivated secondary alkyl halides with alkylboranes provides an efficient way to construct alkyl-alkyl bonds. The mechanism of this reaction with the Ni/L1 (L1=trans-N,N'-dimethyl-1,2-cyclohexanediamine) system was examined for the first time by using theoretical calculations. The feasible mechanism was found to involve a Ni(I)-Ni(III) catalytic cycle with three main steps: transmetalation of [Ni(I)(L1)X] (X=Cl, Br) with 9-borabicyclo[3.3.1]nonane (9-BBN)R(1) to produce [Ni(I)(L1)(R(1))], oxidative addition of R(2) X with [Ni(I)(L1)(R(1))] to produce [Ni(III)(L1)(R(1))(R(2))X] through a radical pathway, and C-C reductive elimination to generate the product and [Ni(I)(L1)X]. The transmetalation step is rate-determining for both primary and secondary alkyl bromides. KOiBu decreases the activation barrier of the transmetalation step by forming a potassium alkyl boronate salt with alkyl borane. Tertiary alkyl halides are not reactive because the activation barrier of reductive elimination is too high (+34.7 kcal mol(-1)). On the other hand, the cross-coupling of alkyl chlorides can be catalyzed by Ni/L2 (L2=trans-N,N'-dimethyl-1,2-diphenylethane-1,2-diamine) because the activation barrier of transmetalation with L2 is lower than that with L1. Importantly, the Ni(0)-Ni(II) catalytic cycle is not favored in the present systems because reductive elimination from both singlet and triplet [Ni(II)(L1)(R(1))(R(2))] is very difficult.

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“…The nitrones were found to be light sensitive [14] and hygroscopic [15]. Hence they were stored in the dark until further use.…”

Section: Synthesismentioning

confidence: 99%

Synthesis of Novel Isoxazolidine Derivatives and Their Antifungal and Antibacterial Properties

Kumar

Mallesha

Rangappa

2003

Archiv der Pharmazie

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The synthesis of some biologically interesting isoxazolidine derivatives has been accomplished by the cycloaddition reaction of C-(4-biphenyl)-N-(3-methylphenyl) nitrone and C-(4-biphenyl)-N-(3-chlorophenyl) nitrone to monosubstituted alkenes. The compounds were screened for their antibacterial and antifungal activities. Among the tested compounds 3a (ii), 3a (vii), 3a (viii), 3b (iv), 3b (vii), and 3b (viii) showed significant antifungal activity comparable with that of the standard drug Nystatin against Botrydiplodia theobromae.

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Communications - Preparation of Oxaziranes by Irradiation of Nitrones

Cited by 105 publications

References 0 publications

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

Theoretical Study on the Mechanism of Ni‐Catalyzed Alkyl–Alkyl Suzuki Cross‐Coupling

Synthesis of Novel Isoxazolidine Derivatives and Their Antifungal and Antibacterial Properties

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