Improved Synthesis of Functional CTVs and Cryptophanes Using Sc(OTf)3 as Catalyst
摘要:
Functional cyclotriveratrylene (CTV) and cryptophane derivatives are synthesized in the presence of scandium triflate [Sc(OTf)(3)]. This route allows the preparation of new derivatives that could not be prepared or easily obtained by using the previously reported experimental procedures. With a catalytic amount of scandium triflate (1% mol), CTVs were obtained with yields similar to or higher than those reported previously in reactions run under strong acidic conditions. Cryptophanes were also synthesized in fairly good yields by performing the ring-closure step in the presence of a stoichiometric amount of Sc(OTf)(3). Interestingly, this novel approach strongly reduces the formation of side products and gives rise to novel functionalized molecules for the construction of supramolecular host-guest systems.
Synthesis of Deuterium-Labeled Cryptophane-A and Investigation of Xe@Cryptophane Complexation Dynamics by 1D-EXSY NMR Experiments
摘要:
We present the synthesis of a series of deuterated cryptophanes 2-6 by a slightly modified procedure used for cryptophane-A. We show that for [Xe@cryptophane] complexes the use of variable-temperature one-dimensional 129Xe magnetization transfer (1D-EX-SY) allows the measurement of exchange rates. From these data the decomplexation activation energy Ea has been estimated to be 37.5+/-2 kJ mol(-1). The decomplexation activation enthalpy, deltaH(++) = 35.5+/-2 kJ mol(-1), and entropy, deltaS(++) = -60+/-5 J mol(-1) K(-1), have also been calculated. The calculated negative activation entropy suggests that the activated complex associated with decomplexation is conformationally more strained than the complex in its ground state.
Improved Synthesis of Functional CTVs and Cryptophanes Using Sc(OTf)<sub>3</sub> as Catalyst
作者:Thierry Brotin、Vincent Roy、Jean-Pierre Dutasta
DOI:10.1021/jo050495g
日期:2005.8.1
Functional cyclotriveratrylene (CTV) and cryptophane derivatives are synthesized in the presence of scandium triflate [Sc(OTf)(3)]. This route allows the preparation of new derivatives that could not be prepared or easily obtained by using the previously reported experimental procedures. With a catalytic amount of scandium triflate (1% mol), CTVs were obtained with yields similar to or higher than those reported previously in reactions run under strong acidic conditions. Cryptophanes were also synthesized in fairly good yields by performing the ring-closure step in the presence of a stoichiometric amount of Sc(OTf)(3). Interestingly, this novel approach strongly reduces the formation of side products and gives rise to novel functionalized molecules for the construction of supramolecular host-guest systems.
Synthesis of Deuterium-Labeled Cryptophane-A and Investigation of Xe@Cryptophane Complexation Dynamics by 1D-EXSY NMR Experiments
We present the synthesis of a series of deuterated cryptophanes 2-6 by a slightly modified procedure used for cryptophane-A. We show that for [Xe@cryptophane] complexes the use of variable-temperature one-dimensional 129Xe magnetization transfer (1D-EX-SY) allows the measurement of exchange rates. From these data the decomplexation activation energy Ea has been estimated to be 37.5+/-2 kJ mol(-1). The decomplexation activation enthalpy, deltaH(++) = 35.5+/-2 kJ mol(-1), and entropy, deltaS(++) = -60+/-5 J mol(-1) K(-1), have also been calculated. The calculated negative activation entropy suggests that the activated complex associated with decomplexation is conformationally more strained than the complex in its ground state.