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Asymmetric intramolecular [2 + 2] photocycloadditions: alpha- and beta-hydroxy acids as chiral tether groups 总被引:1,自引:0,他引:1
Faure S Piva-Le-Blanc S Bertrand C Pete JP Faure R Piva O 《The Journal of organic chemistry》2002,67(4):1061-1070
Chiral alpha- and beta-hydroxy acids such as (S)-lactic acid, (S)-phenyllactic acid, (S)-mandelic acid, or (3R)-3-hydroxybutyric acid have been used as tether groups for intramolecular and diastereoselective [2 + 2] photocycloaddition of 3-oxocyclohexene carboxylic acid derivatives. Total regiocontrol toward the straight adduct and high diastereoselectivities (up to 94%) were observed in the case of butenyl lactate 11. After separation of the two diastereoisomers, cleavage of the chiral tether under basic conditions afforded cyclobutane lactones in good yield and enantiomeric pure form. An X-ray structure has been recorded that confirmed the relative and absolute configuration of the three contiguous stereogenic centers assigned according to CD spectra. 相似文献
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Thiomaleimides, generated by the addition of bromomaleimides to thiols including cysteine, undergo highly efficient [2+2] photocycloadditions. 相似文献
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The stereoselectivity in [2+2] photocycloaddition was studied on System I. Compounds
,
, and
cyclize in high yield and the selectivity is higher than 94%. 相似文献
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The regio- and stereoselectivity of intramolecular [2 + 2] photocycloadditions of 2'-hydroxyenones are shown to be solvent-dependent. In the presence of aprotic solvents, 2'-hydroxyenones undergo photocycloadditions in a manner consistent with the presence of an intramolecular hydrogen bond between the carbonyl group and the tether's hydroxy functionality. In protic solvents, intermolecular interactions appear to disrupt the intramolecular hydrogen bond, providing products with complementary diastereoselectivity. If the facial accessibility of the alpha-tethered olefin is limited, the cycloadditions proceed to give head-to-tail or head-to-head regioisomers, depending on the nature of the solvent employed. 相似文献
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Electrochemical reduction of 2,2-dibromo-1,3-diketones in the presence of olefins afforded the [3+2] cycloadducts, 2,3-dihydrofuran derivatives, regioselectively. 相似文献
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Irradiation of 2-cyanochromone in the presence of olefins gave rise to [3 + 2] cycloadducts together with the formation of normal [2 + 2] cycloadducts with the product ratio being temperature-dependent. The mechanism involving a vinyl nitrene intermediate was proposed. 相似文献
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Kobayashi S Shimizu H Yamashita Y Ishitani H Kobayashi J 《Journal of the American Chemical Society》2002,124(46):13678-13679
Catalytic asymmetric intramolecular [3 + 2] cycloaddition of hydrazone/olefins has been attained. In the presence of a chiral zirconium catalyst prepared from zirconium alkoxide and a BINOL derivative, the desired pyrazolidine derivatives were obtained in high yields with high selectivities. The products were easily converted to 1,3-diamine or beta-aminonitrile derivatives by N-N bond cleavage. 相似文献
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Chun Ma Jia‐Yu Zhou Yi‐Zhu Zhang Dr. Guang‐Jian Mei Prof. Dr. Feng Shi 《Angewandte Chemie (International ed. in English)》2018,57(19):5398-5402
The first catalytic asymmetric [2+3] cyclization of azlactones with azonaphthalenes has been established. This strategy allowed the synthesis of a variety of chiral isatin derivatives in generally good yields and excellent enantioselectivities (up to 99 % yield, 98 % ee). The developed reaction has not only established a catalytic enantioselective [2+3] cyclization using azlactones as two‐carbon building blocks, but also enriches the chemistry of catalytic asymmetric cyclizations of azonaphthalenes. In addition, this protocol will provide a useful method for constructing enantioenriched 3,3′‐disubstituted isatin‐type frameworks. 相似文献
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Shū Kobayashi Ryoji HirabayashiHaruka Shimizu Haruro IshitaniYasuhiro Yamashita 《Tetrahedron letters》2003,44(16):3351-3354
[3+2] Cycloaddition between hydrazones and olefins was accelerated in the presence of a stoichiometric amount of BF3·OEt2 or a catalytic amount of Zr(OTf)4, Hf(OTf)4, or Sc(OTf)3 under mild conditions. The corresponding pyrazolidine derivatives were obtained in moderate to high yields using this novel [3+2] Lewis acid catalysis. 相似文献
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Kusama H Funami H Shido M Hara Y Takaya J Iwasawa N 《Journal of the American Chemical Society》2005,127(8):2709-2716
Novel tungsten-containing carbonyl ylides 7, generated by the reaction of the o-alkynylphenyl carbonyl derivatives 1 with a catalytic amount of W(CO)(5)(thf), reacted with alkenes to give polycyclic compounds 5 through [3 + 2]-cycloaddition reaction followed by intramolecular C-H insertion of the produced nonstabilized carbene complex intermediates 8. In the presence of triethylsilane, these tungsten-containing carbene intermediates 8 were smoothly trapped intermolecularly by triethylsilane to give silicon-containing cycloadducts 17 with regeneration of the W(CO)(5) species. By this procedure, the scope of alkenes employable for this reaction was clarified. The presence of the tungsten-containing carbonyl ylide 7c was confirmed by direct observation of the mixture of o-ethynylphenyl ketone 1c and W(CO)(5)(thf-d(8)). Careful analysis of the intermediate by 2D NMR, along with the observation of the direct coupling with tungsten-183 employing the (13)C-labeled substrate, confirmed the structure of the ylide 7c. Examination using (E)- or (Z)- vinyl ether revealed that the [3 + 2]-cycloaddition reaction proceeded in a concerted manner and that the facial selectivity of the reaction differed considerably depending on the presence or absence of triethylsilane. These results clarified the reversible nature of this [3 + 2]-cycloaddition reaction. 相似文献
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Irradiation of a series of [4.4.3]propella-3,8-dienes which differ in the structure of the 5-membered hetero-ring gives in most cases competing intramolecular [2+2] photocycloaddition yielding cage products along with the intermolecular addition products whose configurations were not determined. 相似文献
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Irradiation of 3-pentyn-2-one (1) in the presence of tetramethylethylene, isobutylene, and cis- and trans -2-butene leads to vinyldihydrofurans 3,5,6, 8 and 9 (Table 1) in a novel [3 + 2] photochemical cycloaddition reaction. A related adduct 13 is formed between tetramethylethylene and 5,5-dimethyl-3-hexyn-2-one (2). A mechanism incorporating an initial biradical that closes to a carbene (eqn 3) is proposed to account for these reactions. 相似文献
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Joseph BK Verghese B Sudarsanakumar C Deepa S Viswam D Chandran P Asokan CV 《Chemical communications (Cambridge, England)》2002,(7):736-737
The conformational change induced by the introduction of a ketenedithioacetal moiety at C-4 of 1,7-substituted-1,6-heptadiene-3,5-diones results in favorable spatial relationships between the alkenoyl groups to effect efficient intramolecular cycloadditions: irradiation of bis(alkenoyl)ketenedithioacetals in solution leads to facile and stereospecific intramolecular [2 + 2] photocycloadditions resulting in the formation of substituted bicyclo[3.2.0]heptane-2,4-diones, the observed conformational rigidity of which is attributed to the push-pull character of the ketenedithioacetal group. 相似文献
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[structure: see text]. We report a new methodology for the construction of novel and uniquely shaped 3-azabicyclo[4.2.0]octan-4-one derivatives by combining the Ugi multicomponent reaction with [2+2] enone-olefin photochemical transformations. The overall sequence is capable of creating up to five stereocenters; however, in most cases, only two diastereomers are observed. 相似文献
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Photochemical cycloaddition of cyclopentene with enone esters containing different chiral auxiliaries yielded anti and syn adducts and in good yield and with moderate to high (79%) enantiomeric excesses. 相似文献
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A novel, mild, robust catalyst Y(OTf)(3) for C-C bond heterolysis of N-tosyl aziridines was developed and the resulting metallo-azomethine ylides may readily undergo [3+2] dipolar cycloaddition with an electron-rich olefin via a stepwise reaction pathway with high regio- and diastereoselectivity leading to substituted pyrrolidines. 相似文献