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41.
Biswanath Das Joydeep Banerjee Nikhil Chowdhury Anjoy Majhi Gurram Mahender 《Helvetica chimica acta》2006,89(5):876-883
A simple and convenient synthesis of five important insect pheromones by means of Baylis–Hillman adducts is described, i.e., of (2E,4S)‐2,4‐dimethylhex‐2‐enoic acid ( 1 ), a mandibular‐gland secretion of the male carpenter ant in the genus Camponotus, of (+)‐(S)‐manicone ( 2 ) and (+)‐(S)‐normanicone ( 3 ), two mandibular‐gland constituents of Manica ants, and of (+)‐dominicalure‐I ( 6 ) and (+)‐dominicalure‐II ( 7 ), two aggregation pheromones of the lesser grain borer Rhyzopertha dominica (F). For the first time, the potential of the Baylis–Hillman chemistry for the stereoselective synthesis of trisubstituted olefins was successfully applied to the synthesis of these pheromone compounds. 相似文献
42.
Monisha Singha Manasi Maji Manish Gupta Srijoni Majhi Amit Basak 《Tetrahedron letters》2019,60(14):945-947
Garratt-Braverman (GB) cyclization, two CC bond forming reaction in a single step, has been utilized to construct several isoindoline and phthalan derivatives. The precursors were the bispropargyl protected amines and ethers with one of the propargyl arm substituted with an alkene moiety. The GB cyclizations were generally carried out in presence of DBU in refluxing toluene. In case of the bispropargyl amine systems with the alkene arm substituted with electron withdrawing ester group, the cyclization occurred at room temperature. The yields of cyclization ranged from 64 to 86% which are acceptable considering the formation of two CC bonds. The protected isoindolines could be successfully deprotected by treatment with thiophenol in presence of triethyl amine and the corresponding free amines were isolated as the TFA salts. 相似文献
43.
Biswanath Das Nikhil Chowdhury Joydeep Banerjee Anjoy Majhi 《Tetrahedron letters》2006,47(37):6615-6618
An efficient one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids has been accomplished by treatment of unactivated Baylis-Hillman adducts, 3-hydroxy-2-methylenealkanoates, with Al-NiCl2·6H2O in methanol at room temperature followed by hydrolysis. The method has been applied to the synthesis of three important insect pheromones, (4S,2E)-2,4-dimethyl-2-hexenoic acid, (+)-(S)-manicone and (+)-(S)-normanicone. 相似文献
44.
Biswanath Das Joydeep Banerjee Anjoy Majhi Gurram Mahender 《Tetrahedron letters》2004,45(50):9225-9227
A convenient and facile stereoselective synthesis of (E)- and (Z)-trisubstituted alkenes has been achieved by treatment of unactivated Baylis-Hillman adducts with NaBH4 in the presence of CuCl2·2H2O at room temperature for 15 min. 相似文献
45.
A simple and efficient one‐pot method has been developed for the synthesis of α‐aminonitriles by concurrent reaction of aldehydes, amines and trimethylsilyl cyanide with a catalytic amount of NbCl5 (10 mol%) in CH3CN at room temperature. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
46.
Direct conversion of methane to higher hydrocarbons is an effective process to solve the problem of natural gas utilization. Although remarkable progress has been achieved on the dehydro-aromatization of methane (DAM), low conversion caused by severe thermodynamic limitations, coke formation, and catalysis deactivation remain important drawbacks to the direct conversion process. Molybdenum catalysts supported on HZSM-5 type zeolite support are among the most promising catalysts. This review focuses on the aspects of direct methane conversion, in terms of catalysts containing metal and support, reaction conditions, and conversion in different types of reactors. The reaction mechanism for this catalytic process is also discussed. 相似文献
47.
Baylis-Hillman adducts on treatment with triethyl orthoacetate in the presence of HClO4-SiO2 afford the corresponding allyl ethyl ethers while in the presence of NaHSO4-SiO2 undergo the Johnson-Claisen rearrangement to form ethyl alk-4-enoates. Thus two different types of trisubstituted alkenes are produced in a stereoselective manner using two different hetereogeneous catalysts. 相似文献
48.
Maiti Tushar Kanti Singh Jitendra Maiti Subrata Kumar Ahuja Arihant Dixit Prakhar Majhi Jagannath Bandyopadhyay Anasuya Chattopadhyay Sujay 《Journal of Solid State Electrochemistry》2022,26(11):2565-2583
Journal of Solid State Electrochemistry - A novel technique for improving the characteristics of proton exchange membranes (PEMs) for fuel cell applications has been proposed, which combines... 相似文献
49.
The present work deals with the possibility of propagation of torsional surface wave in an inhomogeneous crustal layer over an inhomogeneous half space. The layer has inhomogeneity which varies linearly with depth whereas the inhomogeneous half space exhibits inhomogeneity of three types, namely, exponential, quadratic, and hyperbolic discussed separately. The dispersion equation is deduced for each case in a closed form. For a layer over a homogeneous half space, the dispersion equation agrees with the equation of the classical case. It is observed that the inhomogeneity factor due to linear variation in density in the inhomogeneous crustal layer decreases as the phase velocity increases, while the inhomogeneity factor in rigidity has the reverse effect on the phase velocity. 相似文献
50.
The paper studies the propagation of torsional surface waves in an initially stressed anisotropic poro-elastic layer over a semi-infinite heterogeneous half space with linearly varying rigidity and density due to irregularity at the interface. The irregularity is taken in the half space in the form of a rectangle. It is observed that torsional surface waves propagate in this assumed medium. In the absence of the irregularity, the velocity equation of the torsional surface wave is also obtained. For a layer over a homogeneous half space, the velocity of torsional surface waves coincides with that of the Love waves. 相似文献