- Elaboration of 1-benzoyltetrahydroisoquinoline derivatives employing a Pictet-Spengler cyclization with α-chloro-α-phenylthioketones. Synthesis of O-methylvelucryptine
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The reaction of N-tosyl-β-phenethylamines with α-chloro-α-phenylthioketones, leading to 1-benzoyl- and 1-pivaloyl-tetrahydroisoquinolines under modified Pictet-Spengler conditions, is described. The synthesis of O-methylvelucryptine employing this transformation as a key step is reported.
- Silveira, Claudio C,Bernardi, Carmem R.,Braga, Antonio L.,Kaufman, Teodoro S.
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p. 8947 - 8950
(2007/10/03)
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- Effects of adjacent acceptors and donors on the stabilities of carbon-centered radicals
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The radical stabilization energies (RSEs) for 21 radicals, GCH2*, where G is an electron donor or acceptor group, were estimated from differences in homolytic C-H bond dissociation energies (ABDEs relative to that of methane). These RSEs were found to agree reasonably well in order with theoretically calculated RSEs that have been reported and with those obtained by averaging RSEs from nine different methods (a literature RRSx scale). But the RSEs estimated from ΔBDEs were almost without exception larger because the theoretical calculations and RRSx method greatly underestimate the size of most RSEs. The RSEs for GCH2* radicals were found to be enhanced to the extent that G is able to delocalize an odd electron on an adjacent carbon atom and were diminished by the presence of electron-withdrawing properties in G. Most groups stabilize the radical, but when the electron-withdrawing effect of the group is large, as in F3C? and Me3N+CH2? radicals, the net effect is to destabilize the radical relative to the methyl radical. The RSEs of 12 radicals of the type RSC?HG or PhSC?HG, relative to that of the GCH2? radical, were found to increase progressively as the acceptor group G was changed along the series Ph, fluorenyl (Fl), CO2Et, CN, COMe, and COPh. The RSEs of these donor-acceptor radicals were all smaller than the sum of the RSEs of the singly-substituted radicals, GCH2? and PhSCH2? (or RSCH2?). The effects of a second PhS or like donor and of a second acceptor on the RSEs were also determined. Examination of the RSEs of GC?(Ph)CN radicals indicates that the interactions of G and CN in the GC?CN moieties, with G = MeO, EtS, or c-C5H10N, are not synergistic as has been claimed from ESR studies.
- Bordwell,Zhang, Xian-Man,Alnajjar, Mikhail S.
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p. 7623 - 7629
(2007/10/02)
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- Mono halogenation of β-keto sulfides. Synthesis of β-keto-α-phenylthio p-tolyl sulfones
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β-Keto-α-phenylthio p-Tolyl sulfones are obtained from β-keto-alkyl phenyl sulfides by halogenation with NCS followed by treatment with sodium p-toluene sulphinate.
- Fortes,Coimbra
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p. 2039 - 2044
(2007/10/02)
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- Cationic Polar Cycloadditions of Phenylthionium Ions with Olefines: A New Route to Thiochromans
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Reaction of 2-chloro-N,N-dimethyl-2-(phenylthio)acetamide (1a) with styrene in the presence of stannic chloride gave 3,4-dihydro-N,N-dimethyl-4-phenyl-2H-1-benzothiopyran-2-carboxamide.The same benzothiopyran was also obtained from N,N-dimethyl-2-(phenylsulfinyl)acetamide and styrene under the Pummerer reaction conditions, but in lower yield.Similarly, α-chlorosulfides derived from ethyl 2-(phenylthio)acetate, 2-(phenylthio)acetonitrile, 1-(phenylthio)-2-propanone, and thioanisole reacted with styrene to give the corresponding 4-phenylbenzothiopyrans in variable yields.The reaction of 1a with trans-stilbene gave the expected benzothiopyran derivative, but the reaction of 1a with 1,1-diphenylethylene and phenylacetylene showed some variation of the reaction course.This cycloaddition reaction was extended to the intramolecular case.A possible mechanism for the formation of the benzothiopyran is discussed.
- Ishibashi, Hiroyuki,Okada, Motofumi,Sato, Kazumi,Ikeda, Masazumi,Ishiyama, Ko-ichi,Tamura, Yasumitsu
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- REGIOSPECIFIC SYNTHESIS OF α-(PHENYLTHIO)CYCLOALKENONES AND OF α-PHENYL-α-(PHENYLTHIO)KETONES VIA αα-ADDITION OF PHENYLSULPHENYL CHLORIDE TO α-DIAZOKETONES
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Cyclic α-diazoketones react with phenylsulphenyl chloride at room temperature to furnish α-chloro-α-(phenylthio)cycloalkanones which undergo ready dehydrochlorination to α-(phenylthio)cycloalkenones when treated with triethylamine; acyclic, terminal α-diazoketones also furnish α-chloro-α-(phenylthio)adducts which are useful electrophiles in the synthesis of α-phenyl-α-(phenylthio)ketones.
- McKervey, M. Anthony,Ratananukul, Piniti
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p. 117 - 120
(2007/10/02)
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- PHOTOCHEMICAL RING CLOSURE OF α,α-BISULFENYLATED CARBONYL COMPOUNDS STEREOSELECTIVE FORMATION OF CIS-DIHYDROBENZOTHIOPHENES
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Photochemistry of α,α-bisulfenylated ketone has been investigated.Irradiation of 2-phenylthiodihydrothiophen-3-one (1) in benzene gave the radical recombination products 9 (63percent) and 10 (49percent).In a polar solvent, the ionic chemistry became predominant.Brief irradiation of 1 in acetonitrile and methanol gave the cis-fused dihydrothiophene 11 as the major product in 43percent and 20percent yields, respectively.The stereoselective photocyclization was generally observed for other ketones (2-8) in acetonitrile solution (Table 1).The photoproducts were easily dehydrated by treating with boron trifluoride etherate to give the corresponding benzothiophenes in high yields.Simple α-phenylthioketones are photoinert under the same conditions.The mechanism of this novel photocyclization of bisulfenylated ketones is also discussed.
- Sasaki, Tadashi,Hayakawa, Kenji,Nishida, Sumio
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