Intramolecular exchange of trimethylsilyl group in trimethylsilylesters of nitronic acids

Ioffe, Sema L.; Shitkin, V. M.; Khasapov, B. N.; Kashutina, M. V.; Тартаковский, В. А.; Myagi, M. Ya.; Lippmaa, É.

doi:10.1007/bf00929421

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…Assuming the mechanism for [3+3]‐cycloaddition, nitroso acetals 3 should be considered as kinetic products as exemplified in Scheme . Silyl nitronates are known to exist as equilibrating mixtures of trans ( 1‐A ) and cis ( 1‐B ) isomers . The trans isomer 1‐A is more stable than the cis isomer 1‐B for steric reasons.…”

Section: Resultsmentioning

confidence: 99%

Six‐Membered Cyclic Nitroso Acetals: Synthesis and Studies of the Nitrogen Inversion Process of N‐Silyloxy‐3,6‐dihydro‐2H‐1,2‐oxazines

et al. 2016

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Silyl nitronates undergo rhodium‐catalyzed formal [3+3]‐cycloaddition with enol diazoacetates to form N‐silyloxy‐3,6‐dihydro‐2H‐1,2‐oxazines. The scope of the reaction and the extent of the major side process were evaluated. A mechanistic scheme was proposed. The nitrogen inversion barrier in the obtained nitroso acetals was estimated based on both quantum calculations and kinetic measurements.

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Section: Resultsmentioning

confidence: 99%

Six‐Membered Cyclic Nitroso Acetals: Synthesis and Studies of the Nitrogen Inversion Process of N‐Silyloxy‐3,6‐dihydro‐2H‐1,2‐oxazines

et al. 2016

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“…LDA in THF at −78 °C gave almost same result as DBU at 0 °C. The existence of E - and Z -isomerism of 3b further confirmed that the product of the reaction between 1b and trimethyl phosphite is oxime 2b but not the nitronic acid, because it has been well established that the silyl nitronate does not show E - and Z -isomerism …”

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confidence: 69%

Dialkyl (1-Hydroxyiminoalkyl)phosphonates from 1-Bromo-1-nitroalkanes and Trialkyl Phosphites

et al. 1999

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Preparation and reactions of silyl nitronates derived from 2,2,2‐trifluoronitroethane. Diastereoselective synthesis of trifluoromethyl‐substituted aminoethanols and ‐propanols

Martí¹,

Heinzer²,

Seebàch³

1995

Liebigs Ann./Recl.

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Silyl nitronates of 2,2,2-trifluoronitroethane and of l,l,l-trifluoro-2-nitropropane [SiMe3, SiMez(tBu), SiMezCMezCHMez] were prepared and their reactions studied. -The TBDMS nitronate of the nitroethane is present as the ( E ) and (Z) isomer (2.3:l at room temperature; EA = 9.3 kcal mol-l for their isomerization). Bu4NF-catalyzed silyl nitro aldol additions to aldehydes show reasonable selectivities for the formation of the syn diastereoisomers of 5-13 (ca. 4 : l ; with the non-fluorinated analogs anti isomers prevailing!). The anti epimers (5-9, 12, 13, 1?-20) in the trifluoromethyl series can be prepared by diastereoselective protonation of the corresponding 0-silyl lithium nitronates (ca. 9: 1, Scheme 3). Careful reduction of the NOz groups (Hz/Raney nickel) gives trifluoroamino alcohol derivatives (22-30, Scheme 4). -The trimethylsilyl nitronates are also used for 1,3-dipolar cycloadditions (to 1-hexene, styrene, methyl vinyl ketone, and acrylates) to give N-(sily1oxy)isoxazolidines (32-40; Scheme 5). The configuration of the major products (2,3-cis, 3,5-trans) was derived from NMR measurements, X-ray structure determinations, and thermal equilibration studies. The major course of reaction was thus derived to be an exo approach of the dipolarophiles to the (Z)-silyl nitronates (Scheme 8). -Some conversions of the W(sily1oxy)isoxazolidines (treatment with acid, base, and Raney nickel) are also described (products 42-51).Since the first report published in the early 1970s by Joffe and Tartakovskii[21, silyl nitronates of type A have become versatile reagents in synthetic organic chemistry [3]. They have found broad applications as 1,3-dipoles in 13 + 21 cycloadditi~ns[~~~] yielding isoxazolidines or, after loss of silanol, A2-isoxazolines. Silyl nitronates A are in this case synthetic equivalents of nitrile oxides, and the formed heterocycles are not only precursors to amino alcohols, but also to P-hydroxy ketones (an alternative access to aldol~[~I). On the other hand, mediated by fluoride ions, primary silyl nitronates A (R2 = H) undergo highly diastereoselective additions to aldehydes with the formation of erythro O-silylated nitro (nitro aldolsr71, cf. Henry reaction). Further examples of the reactions of silyl nitronates have been collected in some extensive review articled3].Because of the importance of fluorine-containing molecules in chemical and pharmaceutical trifluoromethyl-substituted building blocks, such as the fluoro nitro alkanes 1 and 2191 have attracted significant interest. In previous work, Baasner's group[l0I and ours ["] have described the use of 1 and 2 in aldol and Michael additions. However, the observed diastereoselectivity for the aldol addition to aldehydes was usually low. Another approach would be to use silyl nitronates 3 and 4. However, previous attempts led to mixed results with these compounds: specifically, 4a was prepared by deprotonation and trapping with tert-butyldimethylsilyl chloride on one occasion, but the experiment was not reproducible[llb1. In this paper, we repor...

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Intramolecular exchange of trimethylsilyl group in trimethylsilylesters of nitronic acids

Cited by 5 publications

References 3 publications

Six‐Membered Cyclic Nitroso Acetals: Synthesis and Studies of the Nitrogen Inversion Process of N‐Silyloxy‐3,6‐dihydro‐2H‐1,2‐oxazines

Six‐Membered Cyclic Nitroso Acetals: Synthesis and Studies of the Nitrogen Inversion Process of N‐Silyloxy‐3,6‐dihydro‐2H‐1,2‐oxazines

Dialkyl (1-Hydroxyiminoalkyl)phosphonates from 1-Bromo-1-nitroalkanes and Trialkyl Phosphites

Preparation and reactions of silyl nitronates derived from 2,2,2‐trifluoronitroethane. Diastereoselective synthesis of trifluoromethyl‐substituted aminoethanols and ‐propanols

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