摘要:

AbstractThe experimental (PES) and calculated (MNDO) ionization potentials of the three geometric isomers of 3,3,4,4‐tetramethyl‐1,2‐bis(methoxyimino)cyclobutane [E,E)‐, (E,Z)‐ and (Z,Z)‐1] are reported. The derived electronic structures are compared with those of the three isomeric five‐membered ring homologues2. The three different orientations of the two methoxy groups in 1 have only a small effect on the energy of the π levels since the three isomers of 1 are planar [or, as in the (Z, Z)‐isomer, almost so], but they have a significant effect on the order of then+andn−levels. The variations in the lone‐pair order are discussed in terms of through‐bond and thro

ISSN:0165-0513    

DOI:10.1002/recl.19911100102

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reactions of formic acid with and without addition of sodium formate with diphenylmethanol (4) and chlorodiphenylmethane (3) were compared to those with hydroxydiphenylacetic (benzilic) acid (12a) and chlorodiphenylacetic acid (14a). Formic acid did not favour anySNl‐type reaction on4, but a strong catalysis by iodide ion was observed. Sodium formate rapidly performed the substitution of the chlorine in3. A similar outcome was obtained with chloro acid14a, but the rationalization of the results is different. Chloro acid14aand its methyl ester14bwere prompt to react, but the equilibria were shifted to α‐formyloxy products 13 only by the addition of HCOONa. HCOOH was unable to perform any reduction on either 3 and 4 or12aand14a, a fact which was taken as evidence for concerted substitution mechanisms on ion pairs or betaine 15. Mechanistic implications are d

ISSN:0165-0513    

DOI:10.1002/recl.19911100103

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe crystal structures of two pairs of diastereomeric salts consisting of ephedrine and a cyclic phosphoric acid were analyzed in detail. One pair (R = H; Figure 1) shows no difference in solubility, as reflected in identical non‐bonded interaction patterns in the two salts. The other pair (R = CI; Figure 1) shows a significant solubility difference; the crystal packings of these two salts differ considerably. The less soluble salt shows far more favorable Van der Waals interactions, presenting further evidence that the result of optical resolutions by selective crystallization are determined by these weak interactions. This study, in combination with the results presented in the previous paper (Towards a rational design of resolving agents, Part II), suggests that a model might be developed describing a (quantitative) relationship between the lattice energy difference in a diastereomeric pair and the resolution efficiency of the resolving agen

ISSN:0165-0513    

DOI:10.1002/recl.19911100104

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractActivity and selectivity in carbon dioxide hydrogenation reactions depend on the nature of the catalyst support. On alumina, methane is the major reaction product whereas on zinc oxide methanol is formed preferably, however with formation of much carbon monoxide.Kinetic and FTIR measurements show that methanol formation is favored on a ZnO support and reinforce the hypothesis of a direct transformation of carbon dioxide to methanol.

ISSN:0165-0513    

DOI:10.1002/recl.19911100105

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractVarious O‐glycosides were prepared directly from the corresponding aldoses by use of 3 molar equivalents of an alcohol with catalytic amounts of trifluoromethanesulfonic acid (triflic acid) in dimethyl sulfoxid

ISSN:0165-0513    

DOI:10.1002/recl.19911100106

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractTransimination has been used as a key step in a convenient, highlyerythroselective, one‐pot synthesis of N‐substituted β‐ethanolamines from (R)‐(+)‐[(tert‐butyldimethylsilyl)oxy]‐benzeneacetonitrile (OTBS

ISSN:0165-0513    

DOI:10.1002/recl.19911100107

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractReaction of (NPCl2)3(1) with the monosodium salt of uracil in the presence of Bu4NBr as phase‐transfer catalyst gives apart from an uracil phosphazene derivative (N3P3Cl5)2C4N2H2O2(2) appreciable amounts of two hydrolysis products,viz. [N3P3Cl5O] [Bu4N] (3) and an oxygen‐bridged dimer (N3P3Cl5)2O (4).31P NMR data are given as well as the X‐ray structure

ISSN:0165-0513    

DOI:10.1002/recl.19911100108

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19911100110

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19911100101

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY