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Photo-Fries rearrangement reactions of 1-pyrenyl esters were investigated. Photoreaction of 1-pyrenyl benzoate in benzene generates 1-hydroxy-2-pyrenyl phenyl ketone along with 1-pyrenol. The exceptionally down field 1H NMR chemical shift of OH proton in the photoproduct indicates the existence of intramolecular hydrogen bonding. Photorearrangements of analogs that have electron-withdrawing or electron-releasing group on the phenyl ring, and related heteroaromatic carboxylates also take place to form the corresponding ketones. However, photoreactions of 1-pyrenyl aliphatic carboxylate esters do not occur. The results of spectroscopic and theoretical studies suggest the mechanistic pathway for this process is initiated by homolytic CO bond cleavage in an aroyl group localized 1(π?→?π1) excited state of the 1-pyrenyl esters. The radical pair generated in this fashion then undergoes in-solvent-cage coupling to yield the 1-hydroxy-2-pyrenyl aryl ketone selectively. 相似文献
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Mitsunori Honda Tadashi NakajimaMaiko Okada Keita YamaguchiMitsuhiro Suda Ko-Ki KunimotoMasahito Segi 《Tetrahedron letters》2011,52(29):3740-3742
The reaction of acylsilanes with α-sulfinyl carbanions such as α-lithioalkyl sulfoxide is described. The reaction proceeds to give silyl enol ethers preferentially through the initial formation of the α-silyl alkoxide intermediates. In particular, the products derived from enolizable acylsilanes were the regio-defined silyl enol ethers that cannot be obtained by usual enolization of the corresponding unsymmetrical ketones with base. 相似文献
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Mitsunori Honda Tomoyuki Naitou Hiromitsu Hoshino Seiji Takagi Masahito Segi Tadashi Nakajima 《Tetrahedron letters》2005,46(43):7345-7348
Treatment of cyclopropyl silyl ketones with trimethylsilyl trifluoromethanesulfonate as a strong acid having low nucleophilic counter anion gives the corresponding 5-silyl-2,3-dihydrofuran derivatives, exclusively, regardless of substituents on the cyclopropane ring or silicon atom. The resulting 5-silyl-2,3-dihydrofuran derivatives exhibit both reactivities of the vinylsilane and the cyclic enol ether in the subsequent reaction with electrophilic reagents or Heck type reaction. 相似文献
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Li GM Niu S Segi M Tanaka K Nakajima T Zingaro RA Reibenspies JH Hall MB 《The Journal of organic chemistry》2000,65(20):6601-6612
Alpha,beta-unsaturated thioaldehydes and thioketones, R1CH=CH-C(=S)R2, are prepared in situ by the reaction between the corresponding carbonyl compounds and bis(dimethylaluminum) sulfide. These compounds undergo [4 + 2] self-dimerization reactions in which one molecule serves as the heterodiene component and the other as the dienophile to afford different types of dimeric products depending on the R1 and R2: 1,2-dithiin and 1,3-dithiin (R1 = R2 = H), 1,2-dithiin (R1 = Ph, R2 = H, CH3), or dihydrothiopyran (R1 = R2 = Ph). These differences in selectivity are explained on the basis of the relative energies evaluated by molecular orbital (MO) calculations at the DFT (density functional theory) level. The calculations show that in the dimerization reaction of thioacrolein (I), the head-to-tail (S-C-S bonded) dimers are kinetically more stable by about 5 kcal/mol but slightly thermodynamically unstable by about 2 kcal/mol than the head-to-head (S-S bonded) dimers. The calculations on thiocinnamaldehyde (IV) indicate that the dimerization reactions of phenyl-substituted alpha,beta-unsaturated thioaldehydes and thioketones are almost equally controlled by thermodynamic and kinetic factors. These unsaturated thiocarbonyl compounds also function as heterodienes (C=C-C=S) in the cycloaddition reaction with norbornadiene and as dienophiles (C=S) in the reaction with cyclopentadiene. 相似文献
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Mitsunori Honda Kenta NakaeToshiaki Nishizawa Mitsuhiro SudaKo-Ki Kunimoto Masahito Segi 《Tetrahedron》2011,67(49):9500-9508
The reaction of silylcyclopropyl bromides with dichloromethyl methyl ether in the presence of n-butyllithium is investigated. Under basic reaction conditions, the corresponding cyclopropylidene derivatives are exclusively obtained. The resulting cyclopropylidene compounds are subjected to protonolysis or trapping with electrophiles in a one-pot to give the cyclopropyl silyl ketone derivatives in good yields. Acidic treatment of derived cyclopropyl silyl ketone allows isomerization to give the thermodynamically favorable trans form exclusively. 相似文献
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