24161-47-5Relevant academic research and scientific papers
Synchronous enantiomeric enrichment of both reactant and product by absolute asymmetric synthesis using circularly polarized light. Part 1. Theoretical and experimental verification of the asymmetric photoisomerization of methyl norbornadiene-2-carboxylate to methyl quadricyclane-1-carboxylate
Nishino,Nakamura,Inoue
, p. 1693 - 1700 (2001)
We propose a new absolute asymmetric synthesis (NAAS), in which the irradiation with left- or right-handed circularly polarized light (CPL) of a racemic reactant leads to the synchronous enantiomeric enrichment of both reactant and product. NAAS has two subcategories: (a) reversible NAAS (CPL excites both the reactant and the product), (b) irreversible NAAS (only the reactant is excited by CPL). Here in the first paper of this series of papers we consider irreversible NAAS. We have deduced the theoretical equations that determine the relationship between the enantiomeric excesses (ee's) of both reactant and product and the progress of the CPL-induced photoreaction. Using the clear and reversible photoisomerization of chiral methyl norbornadiene-2-carboxylate (I) to chiral methyl quadricyclane-1-carboxylate (II) by CPL-irradiation in acetonitrile, we experimentally verified the equations. The ee's of both reactant and product are remarkably dependent on the anisotropy factor (g = Δε/ε) of the reactant. The ee of the reactant increases to 100% if the irradiation is continued to the stage that nearly all of the reactant is consumed. Conversely, the ee of the product gradually decreases from g/2 during the initial stages to zero at the final stage of the irradiation. This is the first time that the relationship between the ee of product and the progress of the photoreaction is experimentally examined based upon theoretical considerations.
Synchronous enantiomeric enrichment of both reactant and product by absolute asymmetric synthesis using circularly polarized light. Part 3. Numerical simulation and experimental verification of the reversible asymmetric photoisomerization between methyl norbornadiene-2-carboxylate and methyl quadricyclane-1-carboxylate
Nishino,Nakamura,Shitomi,Onuki,Inoue
, p. 1706 - 1713 (2001)
In the first paper of this series, we proposed a new absolute asymmetric synthesis (NAAS) with circularly polarized light (CPL), which can be classified into two subcategories: (a) reversible NAAS (CPL excites both the reactant and product), (b) irreversible NAAS (the reactant only is excited by CPL). In the present paper we deal with reversible NAAS. The numerical simulations, which are based upon the results of the preceding paper of this series, are performed. Using the reversible photoisomerization between methyl norbornadiene-2-carboxylate (I) and methyl quadricyclane-1-carboxylate (II), it was experimentally verified that the enantiomeric excesses (ee's) of both the reactant and product were critically dependant not only on the anisotropy factors (g = Δε/ε) of both components, but also on the relative quantum yields of the forward and reverse reactions. In the case of reversible NAAS, the ee of the reactant and the product will concurrently increase according to the conversion, and attain appreciable values at the photostationary state if we appropriately select the system and the CPL-irradiation wavelength in such a way that if the g factors of the product and the reactant are large enough, the sign of the g factor of the product is opposite to that of the reactant, and the photochemical equilibrium constant K is less than unity.
Experiments towards the Generation of 1,5- and 2,3-Didehydroquadricyclanes
Heywang, Ulrich,Szeimies, Guenter
, p. 121 - 131 (2007/10/02)
Metalation of the (hydroxymethyl)quadricyclanes 7a - c with n-butyllithium in ether is determined mostly by the chelating effect of the CH2O-Li group and only to a lesser extent by the magnitude of the 13C-1H coupling constant of the position to be lithiated in the corresponding quadricyclane derivative.Similar results were obtained for 3-quadricyclanol (20a).Treatment of the bromide 26a, prepared by lithiation of 7b, with strong bases apparently generates the 1,2-didehydroquadricyclane 34.and not the 1,5-didehydroquadricyclane 35.Attempts to convert the dihalide 9 into the 2,3-didehydroquadricyclane 4 were unsuccessful.
Nucleophilic Exchange Reactions at 1-Chloroquadricyclane: 1,5- and 1,7-Dehydroquadricyclane as Reactive Intermediates.
Baumgaertel, Otto,Szeimies, Guenter
, p. 2180 - 2204 (2007/10/02)
Quadricyclane was metalated at position 1 to 1b in high yield by the complex of butyllithium and tetramethylethylenediamine or by a mixture of butyllithium and potassium tert-butoxide.Numerous 1-substituted quadricyclanes were accessible via 1b.Nuclophilic substitution products were obtained by the reaction of 1-chloroquadricyclane with organolithium compounds, lithium amides, and with lithium ethylthiolate (in the presence of a bulky strong base), which could be isomerized to the corresponding norbornadienes.Mechanistic investigations have shown that 1,7- and 1,5-dehydroquadricyclane (4 and 5) were involved as reactive intermediates.The nucleophilic substitution of optical active 1-chloroquadricyclane with lithium dimethylamide proceeded with 96percent racemization.This result is in accord with an elimination-addition mechanism passing over 4 and 5.
