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21.
S. Chandrasekhar 《Tetrahedron letters》2007,48(13):2373-2375
An efficient asymmetric synthesis of (+)-tetrahydropseudodistomin is described. The important synthetic features include a Maruoka asymmetric allylation and a Sharpless asymmetric dihydroxylation as key steps for the generation of chirality at C-2, -4, and -5 of the trisubstituted piperidine ring. 相似文献
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Ch. Raji Reddy N. Kiranmai G. Dattatreya Sarma S. Chandrasekhar 《Tetrahedron letters》2007,48(2):215-218
The first use of hydroxylamine derivatives as the aminoxy equivalent of nucleophiles in palladium catalyzed addition to Baylis-Hillman acetate adducts is described. The reaction proceeds smoothly to give the substituted allyloxy amines in good yield and selectivity. 相似文献
25.
Using a quasi-optical continuously tunable spectrometer in the frequency range of 40–90 GHz (=7.5-3.3 mm) the absorption spectra of the superionic conductors Na-alumina, Ag-alumina,-AgI and CuTeBr have been measured at various temperatures. In the measured spectral range all the materials showed a monotonic increase in the absorption as a function of frequency. These results are discussed in the light of existing theoretical models.Alfred P. Sloan Foundation Fellow 相似文献
26.
The term “liquid crystal” signifies a state of aggregation that is intermediate between the crystalline solid and the isotropic liquid. A substance in this state is strongly anisotropic in some of its properties and yet exhibits a certain degree of fluidity, which in some cases may be comparable to that of an ordinary liquid. A large number of organic compounds are now known to form liquid crystals. An essential requirement for mesomorphism to occur is that the molecules must be highly geometrically anisotropic. The transition to the intermediate state may be brought about by purely thermal processes (thermotropic mesomorphism) o r by the action of solvents (lyotropic mesomorphism). 相似文献
27.
First and practical method for preparing a solid supported 1,3-diol is described starting from commercially available Merrifield's Resin. 相似文献
28.
Observation of Slow Relaxation and Single‐Molecule Toroidal Behavior in a Family of Butterfly‐Shaped Ln4 Complexes
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Sourav Biswas Dr. Sourav Das Tulika Gupta Dr. Saurabh Kumar Singh Dr. Michael Pissas Dr. Gopalan Rajaraman Prof. Vadapalli Chandrasekhar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(51):18532-18550
A family of five isostructural butterfly complexes with a tetranuclear [Ln4] core of the general formula [Ln4(LH)2(μ2‐η1η1Piv)(η2‐Piv)(μ3‐OH)2]?x H2O?y MeOH?z CHCl3 ( 1 : Ln=DyIII, x=2, y=2, z=0; 2 : Ln=TbIII, x=0, y=0, z=6; 3 : Ln=ErIII, x=2, y=2, z=0; 4 : Ln=HoIII, x=2, y=2, z=0; 5 : Ln=YbIII, x=2, y=2, z=0; LH4=6‐{[bis(2‐hydroxyethyl)amino]methyl}‐N′‐(2‐hydroxy‐3‐methoxybenzylidene)picolinohydrazide; PivH=pivalic acid) was isolated and characterized both structurally and magnetically. Complexes 1 – 5 were probed by direct and alternating current (dc and ac) magnetic susceptibility measurements and, except for 1 , they did not display single‐molecule magnetism (SMM) behavior. The ac magnetic susceptibility measurements show frequency‐dependent out‐of‐phase signals with one relaxation process for complex 1 and the estimated effective energy barrier for the relaxation process was found to be 49 K. We have carried out extensive ab initio (CASSCF+RASSI‐SO+SINGLE_ANISO+POLY_ANISO) calculations on all the five complexes to gain deeper insights into the nature of magnetic anisotropy and the presence and absence of slow relaxation in these complexes. Our calculations yield three different exchange coupling for these Ln4 complexes and all the extracted J values are found to be weakly ferro/antiferromagentic in nature (J1=+2.35, J2=?0.58, and J3=?0.29 cm?1 for 1 ; J1=+0.45, J2=?0.68, and J3=?0.29 cm?1 for 2 ; J1=+0.03, J2=?0.98, and J3=?0.19 cm?1 for 3 ; J1=+4.15, J2=?0.23, and J3=?0.54 cm?1 for 4 and J1=+0.15, J2=?0.28, and J3=?1.18 cm?1 for 5 ). Our calculations reveal the presence of very large mixed toroidal moment in complex 1 and this is essentially due to the specific exchange topology present in this cluster. Our calculations also suggest presence of single‐molecule toroics (SMTs) in complex 2 . For complexes 3 – 5 on the other hand, the transverse anisotropy was computed to be large, leading to the absence of slow relaxation of magnetization. As the magnetic field produced by SMTs decays faster than the normal spin moments, the concept of SMTs can be exploited to build qubits in which less interference and dense packing are possible. Our systematic study on these series of Ln4 complexes suggest how the ligand design can help to bring forth such SMT characteristics in lanthanide complexes. 相似文献
29.
Vidya Rani Chandrasekhar Kesavan Mookkandi Palsamy Ravi Lokesh Daniel Thangadurai T. Indra Gandhi N. Rajesh Jegathalaprathaban Rajagopal Gurusamy 《应用有机金属化学》2019,33(3)
Three new metal complexes [Cu(L)2] (1), [Co(L)2] (2) and [Zn(L)2] (3) have been prepared by the reaction of hydrated salts of metal (II) acetate with new Schiff base ligand HL, [2‐((4‐(dimethylamino)phenylimino)methyl)‐4,6‐di‐t‐butylphenol] and characterized by different physico‐chemical analyses such as elemental analysis, single XRD, 1H NMR, FTIR and UV–Vis spectroscopic techniques. Their biomolecular docking, antimicrobial and cytotoxicity studies have also been demonstrated. The proposed structure of Schiff base ligand HL and complex 2 are confirmed by Single crystal X‐ray crystallography study. This analysis revealed that metal (II) complexes remain in distorted tetrahedral coordination environments. The electronic properties such as HOMO and LUMO energies are carried out by gaseous phase DFT/B3LYP calculations using Gaussian 09 program. Complex 1 showed a good binding propensity to the DNA and HSA, during the assessment of docking studies. Schiff base ligand HL and its metal (II) complexes, 1–3 screened for their in vitro antimicrobial activities using the disc diffusion method against selected microbes. Complex 1 shows higher antimicrobial activity than complexes 2, 3 and Schiff base ligand HL. According to the results obtained from the cytotoxic studies, Schiff base ligand HL and its metal (II) complexes 1–3 have better cytotoxicity against MCF‐7 cell lines with potency higher than the currently used chemotherapeutic agent cyclophosphamide. 相似文献
30.
The formal synthesis of (+)-didemniserinolipid B is achieved using Weinreb reaction, Yadav’s chiral propargyl alcohol protocol and hydrolytic ketal formation as the key steps. 相似文献