21592-61-0Relevant academic research and scientific papers
Asymmetric photolysis of 2-phenylcycloalkanones with circularly polarized light: A kinetic model for magnetic field effects
Kohtani, Shigeru,Sugiyama, Masahide,Fujiwara, Yoshihisa,Tanimoto, Yoshifumi,Nakagaki, Ryoichi
, p. 1223 - 1233 (2007/10/03)
Magnetic field effects (MFE) on asymmetric photolysis involving a biradical intermediate have been investigated on a kinetic model where an intersystem crossing (ISC) of the intermediate is taken into account. Changes in the enantiomeric excesses (ee) of chiral substances with circularly polarized light (CPL) irradiation have been simulated, and the necessary conditions for observing the MFE were obtained. The asymmetric photolysis of racemic 2-phenylcycloalkanones (2-PCAs) with CPL has been carried out in both the presence and absence of a magnetic field. Since the anisotropy g factors of 2-PCAs are considerably large, the CPL-induced ee are achieved to a few percent after 90% decomposition though the MFE are not observed. The photolysis mechanism of 2-PCAs in an air-saturated solution has been also clarified. Triplet acyl-benzyl biradicals, formed via photochemical α-cleavage of 2-PCAs, react with O2 dissolved in the solution and result in the formation of acetophenone and alkenoic acids. The bimolecular reactions are diffusion-controlled and the rates are comparable to those of ISC to the singlet biradicals for all 2-PCAs. The recombination yields of the biradicals are sufficiently large. However, the biradical ISC rate shows little magnetic field dependence, which explains the absence of the MFE in this asymmetric photolysis.
(Alkynyl)dicobalt hexacarbonyl-mediated radical cyclizations
Salazar, Karen L.,Nicholas, Kenneth M.
, p. 2211 - 2224 (2007/10/03)
Radicals flanked by the -(alkynyl)Co2(CO)6 unit add intramolecularly to carbon-carbon double bonds with unusual stereo- and regioselectivity. Cationic complex 13a (R=CO2Me) reacts with Zn to produce exclusively the trans-5-exo product 14a. Labile propargyl bromide complexes 16a-d, prepared from the alcohols 7a-d, undergo cyclization with Et3B/O2/Ph2SiH2 or upon irradiation. Under the latter conditions atom transfer products (17a-c, 18c,d) were obtained exclusively, whose regio- and stereochemistry were dependant on the olefinic acceptor. Thus, irradiation of the ester trans-16a or the phenyl derivative 16b (E/Z mixture) gives the trans-cyclopentyl derivatives 17a and 17b; the bromide 16c (R=Me) affords a mixture of the trans-cyclopentyl compound 17c and a comparable amount of the cyclohexyl derivative 18c; and the parent bromide 16d (R=H) is converted exclusively to the cyclohexyl derivative 18d. Heptenyl derivative 20d (R=H) cyclizes exclusively to the 7-endo cycloheptyl derivative 21d. Limited mechanistic experiments suggest the operation of a radical chain, atom transfer mechanism with a product-like transition state. A tandem cyclization/allylation reaction has been demonstrated in the reaction of acyclic bromide 16a with CpFe(CO)2(η1-allyl). (C) 2000 Elsevier Science Ltd.
Synthesis and nematocidal activity of aralkyl- and aralkenylamides related to piperamide on second-stage larvae of Toxocara canis
Kiuchi, Fumiyuki,Nakamura, Norio,Saito, Makiko,Komagome, Kazue,Hiramatsu, Hirokuni,Takimoto, Noriaki,Akao, Nobuaki,Kondo, Kaoru,Tsuda, Yoshisuke
, p. 685 - 696 (2007/10/03)
Seventy-nine aralkyl- and aralkenylamides related to piperamides were synthesized and their nematocidal activity against second-stage larvae of dog roundworm, Toxocara canis, was examined. The activity was greatly dependent on the alkyl chain length and the nature of the amine moiety, but was scarcely affected by the presence or absence of double bond(s) in the chain. The alkyl chain lengths which showed the strongest activity in a series of homologues were m=11 for the pyrrolidine amides and m=13 for the N- methylpiperazine amides. Although piperamides (3,4-methylenedioxyphenyl homologues) showed the strongest activity among the homologues tested, methoxy substituent(s) on the aromatic ring did not have much effect on the activity. However, conversion of the methoxy group to a hydroxy group greatly decreased the activity and shortened the chain length giving the strongest activity. Calculated log P values of non-phenolic aryl-piperamides fell in the range from 3.5 to 4.5, whereas those of hydroxyphenyl-piperamides were smaller, suggesting that different mechanisms are involved in the nematocidal activity of phenolic and non-phenolic compounds.
