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The molybdenum complexes of Schiff base ligands viz. [MoO2LH2O] where L1 = tris(hydroxymethyl)(salicylide-neamino)methane, L2 = tris(hydroxymethyl)(2,3-dihydroxybenzylideneamino)methane and L3 = tris(hydroxymethyl)(2,3,4-trihydroxybenzylideneamino)methane have been synthesized and characterized by spectroscopic and electrochemical techniques. The X-ray crystal structure of the complex [MoO2L1H2O] reveals a distorted octahedral geometry with one ligand and a water molecule coordinated to the MoO2 center. No previous complex of this type contains a coordinated water molecule. The complex undergoes an oxotransfer in the presence of Bu3P to form a -oxobridged molybdenum(V,V) dimer. This rules out Mo—S coordination as a prerequisite for oxotransfer in such molybdenum(VI) complexes. 相似文献
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6-nitro-2'-carbonyl-C-glycofuranosides synthesized via Henry reaction from 1-C-allyl 5-aldo-C-glycoside underwent an intramolecular Michael addition to afford nitrocyclohexanol derivatives in good to excellent yield. Reduction of the nitro group followed by intramolecular amination with ketone and aldehyde and amidation with ester produced indoline and oxindole derivatives, respectively, in excellent yield. 相似文献
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Ahmed Kamal Ahmad Ali Shaik Mahendra Sandbhor M. Shaheer Malik 《Tetrahedron: Asymmetry》2004,15(24):3939-3944
An efficient synthesis of optically active β-azido alcohols from their ketoazides by a one-pot reduction and an in situ lipase resolution protocol is described. The synthetic utility of this procedure has been illustrated by its application in the practical synthesis of both enantiomers of the natural hydroxyamides, tembamide, aegeline and the cardiac drug denopamine, with high enantioselectivities. 相似文献
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An effective one-pot synthesis of polyhydroxylated quinolizidines from 1-C-(2'-oxo-4'-pentenyl)-5-azido-C-glycofuranosides was developed. Reduction of the 5-azido group using triphenylphosphine followed by base treatment produced quinolizidines in good yield. The base-mediated ring-opening beta-elimination produced an acyclic alpha,beta-conjugated ketone as a Michael acceptor, which was followed by an intramolecular nitrogen conjugate addition to form an aza-C-glycopyranoside intermediate. Meanwhile, the beta,gamma-double bond of the aglycon migrated under the basic conditions to form another alpha,beta-conjugated ketone. The subsequent intramolecular conjugate addition by the azasugar nitrogen led to the formation of the quinolizidines in a highly stereoselective manner. The stereoselectivity of the first conjugate addition giving azasugar is affected by the stereochemistry of the monosaccharide substrate, whereas the stereoselectivity in the second conjugate addition was likely directed entirely by steric repulsion from the azasugar. 相似文献
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Ahmed Kamal Mahendra Sandbhor Kaleem Ahmed S. F. Adil Ahmad Ali Shaik 《Tetrahedron: Asymmetry》2003,14(24):3861-3866
A new practical method for the enzymatic synthesis of 1,2-diols has been developed by employing a lipase catalyzed one-pot transesterification protocol. A series of substituted -acetoxyphenylethanones 3a–g have been reduced to the corresponding alcohols under mild conditions employing sodium borohydride and moist neutral alumina, and further subjected for lipase catalyzed irreversible transesterification in the same pot to give mono- and diacetate diols (R)-4 and (S)-5, which on hydrolysis afforded terminal 1,2-diols, (R)- and (S)-6 in high enantiomeric excess. 相似文献
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