- Hydroxy-β-thiolactams to oxazole-2-thiones. A novel dmso-promoted oxidation
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(Chemical Equation Presented) 3-Aryl-3-hydroxy-1-methylazetidine-2-thiones react with HCI in DMSO to give 3-methyl-5-aryloxazole-2-thiones. Substituent effects correlate with rate effects on hydrolyses of acetals of benzaldehyde. An 17O labeling experiment indicates that the oxygen atom of the product is derived from the hydroxyl group. Trifluoroacetic anhydride/DMSO in CH2Cl2 can also promote the reaction. Mechanisms involving a Grob-type fragmentation of an activated substrate, followed by recyclization, or a cyclopropylcarbinyl type of rearrangement can account for this oxidative rearrangement.
- Creary, Xavier,Losch, Andrea
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supporting information; experimental part
p. 4975 - 4978
(2009/05/31)
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- Asymmetric induction during photocyclization of chiral and achiral α-oxoamides within achiral zeolites
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The photochemistry of 31 α-oxoamides capable of undergoing γ-hydrogen transfer has been examined within zeolites. These molecules, upon excitation, yield two products - a β-lactam and oxazolidinone - in solution, both resulting from γ-hydrogen transfer. W
- Natarajan, Arunkumar,Ramamurthy
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p. 4533 - 4542
(2008/09/19)
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- β-Lactam-Forming Photochemical Reactions of N-Trimethylsilylmethyl- and N-Tributylstannylmethyl-Substituted α-Ketoamides
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Two mechanisms have been proposed for the β-lactam-forming photochemical reactions of α-ketoamides. One, suggested by Aoyama, involves excited-state H-atom abstraction while the other, put forth by Whitten, follows a sequential SET-proton-transfer route. The photochemical properties of N-trimethylsilylmethyl- and N-tributylstannylmethyl-substituted α-ketoamides were explored in order to gain information about the mechanism of this process and to develop a regioselective method for β-lactam formation. The results of this effort show that (1) photoreactions of N-trimethyl-silylmethyl-substituted α-ketoamides proceed by competitive H-atom abstraction and sequential SET-desilylation pathways and (2) a sequential SET-destannylation pathway is preferentially followed in photochemical reactions of the tributylstannylmethyl-substituted α-ketoamides.
- Wang, Runtang,Chen, Chuanfeng,Duesler, Eileen,Mariano, Patrick S.,Yoon, Ung Chan
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p. 1215 - 1220
(2007/10/03)
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- Chiral Arrangement of N-Ethyl-N-isopropylphenylglyoxylamide Molecule in Its Own Crystal and in an Inclusion Crystal with a Host Compound and Their Photoreactions in the Solid State That Give Optically Active β-Lactam Derivatives. X-ray Analytical and CD Spectral Studies
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N-Ethyl-N-isopropylphenylglyoxylamide (3c) forms chiral crystal in which its achiral molecules are arranged in a chiral form, and the chirality in the crystal was identified by measurement of the CD spectrum in Nujol mull. Generation of the chirality occurs by twisting of the CO-CO bond of 3c in the crystal. Photoirradiation of the chiral crystal of 3c in the solid state gave optically active β-lactam derivative (4c) of 80% ee. By X-ray analysis, absolute configurations of the chiral crystal and 4c were elucidated. The achiral molecules of 3c are also arranged in chiral forms in inclusion complexes with chiral hosts such as (R,R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[4,4]nonane (5a), (R,R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[5.4]-decane (5b), and their (S,S)-(+)-enantiomers, 6a and 6b, respectively. The crystal structure of a 1:1 inclusion complex of 3c with 5b (7b) was analyzed. Photoirradiation of 7b in the solid state gave (R)-(+)-4c of 85% ee. Photochemical conversions of some other derivatives of 3c to the corresponding β-lactams were also studied. Interestingly, however, irradiation of the 1:1 inclusion complex of N,N-dimethylglyoxylamide (3a) with 5a, which had been prepared by mixing both components in the absence of solvent, gave (R)-(+)-β-lactam (9a) of 45% ee, although the 1:1 complex that had been prepared by recrystallization of the components from toluene gave (S)-(-)-9a of 100% ee. Mixing of powdered chiral (-)-3c crystal with a 2:1 inclusion complex of 5b and MeOH gave a new 1:1 complex of 5b and chiral (+)-3c. The inversion of the chirality of 3c in the solid state was studied by continuous measurements of CD spectra in Nujol mulls.
- Toda, Fumio,Miyamoto, Hisakazu,Koshima, Hideko,Urbanczyk-Lipkowska, Zofia
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p. 9261 - 9266
(2007/10/03)
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- Enantioselective photoreaction in inclusion crystal
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Mixing of powdered chiral hosts and achiral guest compounds gives inclusion complexes in which the latter molecules are arranged in a chiral form. Freezing of the chirality of the guest compounds by photoirradiation in the solid state gives optically active photoreaction products.
- Miyamoto, Hisakazu,Kikuchi, Siro,Oki, Yasuo,Inoue, Mitsuhiro,Kanemoto, Kazuyuki,Toda, Fumio
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- Designs of host/guest molecular and crystal structures
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When an optically active host compound was mixed with an achiral guest compound in the solid state, host-guest inclusion crystals were formed by molecular movement and the achiral molecules became arranged in a chiral form in the inclusion crystals.
- Toda, Fumio
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p. 313 - 316
(2007/10/03)
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- Formation by Mixing of Chiral Host-Achiral Guest Inclusion Complexes in which the Guest Molecules are Arranged in a Chiral Form. Production of Optically Active Photocyclisation Compounds by Irradiation of the Inclusion Complexes
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Mixing of powdered chiral hosts and achiral N,N-dialkylphenylglyoxylamide guest compounds gives inclusion complexes in which the latter molecules are arranged in a chiral form, although such complexes are not obtained by recrystallisation: the chirality of the guest compounds are frozen by photoreaction which gives optically active β-lactams and oxazolidinones.
- Toda, Fumio,Miyamoto, Hisakazu,Kanemoto, Kazuyuki
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p. 1719 - 1720
(2007/10/02)
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- Achiral molecules move and order themselves in a chiral form in host-guest inclusion crystals
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When optically active host compound was mixed with achiral guest compound in the solid state, host-guest inclusion crystals were formed by molecular movement and the achiral molecules became arranged in a chiral form in the inclusion crystals.Mixing of powdered (+)-host crystals with powdered (-)-guest crystals which are formed by a chiral arrangement of achiral guest molecules gave inclusion crystals of (+)-host and the (+)-guest molecules newly produced through an inversion of the (-)-guest molecules during the complexation in the solid state.
- Toda, Fumio,Miyamoto, Hisakazu
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p. 809 - 810
(2007/10/03)
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- Photocyclisation of Phenylglyoxylamides as Inclusion Complexes with an Optically Active Host Derived from Tartaric Acid: Delicate Dependence on the Substituent of the Host and Glyoxylamide
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Optically active β-lactams and/or oxazolidinones have been obtained selectively by photoirradiation of a 1:2 inclusion complex of phenylglyoxylamide with an optically active host derived from tartaric acid.Delicate selectivity which is dependent on substituents in the phenylglyoxylamide and the host is described.
- Toda, Fumio,Miyamoto, Hisakazu,Matsukawa, Rikiya
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p. 1461 - 1462
(2007/10/02)
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