Журнал структурной химии №5 2008 (341,00 руб.)

WIEN2k, an augmented plane wave + local orbital program for calculating crystal properties. <...> Zhurko G.A. ChemCraft tool for treatment of the chemical data // www.chemcraftprog.com 16. .., .., .. . // . . . 2008. 49, 2. . 221 229. 2008. 49, 5 . 851 860 UDC 539.19;547.44 CAMPHOR-BASED D-BROMOKETONES FOR THE ASYMMETRIC DARZENS REACTION: INSIGHTS INTO THE MECHANISM USING DENSITY FUNCTIONAL THEORY 2008 J.Y. Yuan, X.C. Liao, H.M. Wang*, M.S. Tang* Center of Computational Chemistry, Department of Chemistry, Zhengzhou University, Zhengzhou, Henan, P.R. China Received September, 5, 2007 Density functional theory (DFT) calculations at B3LYP/6-31G(d,p) level were carried out to investigate the mechanism of the reaction of benzaldehyde (BA) or acetaldehyde (AD) with (1R)-2-endo-bromoacetyl-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol (endo-2-bromoacetylisoborneol) 1 (Scheme 1). <...> K e y w o r d s: DFT, Darzens condensation, benzaldehyde, acetaldehyde, endo-2-bromoacetylisoborneol, mechanism, transition states, diastereoselectivity, aldol, boat-like, chair-like. <...> Darzens Reaction (Xc = camphor substituent; R = Ph or CH3) One of the premier topics in modern organic chemistry is asymmetric synthesis [ 2 ]. <...> The Darzens condensation reaction represents one of the classical CC and CO bond-forming process [ 1, 7 ]. <...> The first step, the aldol addition reaction, is undoubtedly among the most powerful methods for the formation of carbon-carbon bonds [ 2, 9 ] and hydroxy ketones are commonly prepared by an aldol condensation reaction [ 10 ] or by reductive cleavage of an epoxy ketone. <...> On the basis of Pridgencs results [ 12 ] and those of others [ 2, 9d, 1316 ] to some extent, the following factors govern the energies of the aldol transition states: the steric bulk of the aldehyde [ 2, 9d, 13 ], aromaticity [ 17 ], Lewis basicity as well as substitution pattern of the aldehyde [ 1820 ], the solvent [ 9d, 2023 ], ligands on the metal countercation [ 2, 9d, 13, 22, 2426 ] and possible secondary molecular orbital interactions [ 17a, 27 ]. <...> Furthermore, each IRC was traced to verify every transition state connecting the desired reactants and products. <...> Eventually, the product complex (PC) is produced via transition state 2 (TS2). <...> Table 1 reveals that the activation energy of TS1Q3 is <...>