Inclusion cyclopentanone

The effect of HMPA on the reactivity of cyclopentanone enolate has been examined.44 This enolate is primarily a dimer, even in the presence of excess HMPA, but the reactivity increases by a factor of 7500 for a tenfold excess of HMPA at -50° C. The kinetics of the reaction with CH3I are consistent with the dimer being the active nucleophile. It should be kept in mind that the reactivity of regio- and stereoisomeric enolates may be different and the alkylation product ratio may not reflect the enolate composition. This issue was studied with 2-heptanone.45 Although kinetic deprotonation in THF favors the 1-enolate, a nearly equal mixture of C(l) and C(3) alkylation was observed. The inclusion of HMPA improved the C(l) selectivity to 11 1 and also markedly accelerated the rate of the reaction. These results are presumably due to increased reactivity and less competition from enolate isomerization in the presence of HMPA. 

The formation of crystal inclusion of 47 and 48 with cyclic ketones of suitable ring size (cyclopentanone, cyclohexanone) and with cyclohexene oxide are also important facts. Corresponding inclusion compounds with alcohols or amines could not be obtained. With reference to the heterocyclic guest molecules, the suitability of the ring size is likely to be the decisive factor for guest inclusion. 

Exactly 10 years after the previous statement appeared, the first lithium enolate crystal structures were published as (5) and (6). Thus, structural information derived from X-ray diffraction analysis proved the tetrameric, cubic geometry for the THF-solvated, lithium enolates derived from r-butyl methyl ketone (pinacolone) and from cyclopentanone. Hence, the tetrameric aggregate characterized previously by NMR as (7) was now defined unambiguously. Moreover, the general tetrameric aggregate (7) now became embellished in (5) and (6) by the inclusion of coordinating solvent molecules, i.e. THE. A representative quotation from this 1981 crystal structure analysis is given below. 

Firstly, it was found that 108 forms inclusion complexes with various solvent molecules. In the inclusion complexes with Pr OH, cyclopentanone, 2-cyclopenteno-ne and 2-cyclohexenone, 108 molecules were found to be ordered in a chiral form from measurement of CD spectra in the solid state of the complexes formed. X-ray... 

Scheme 7. Examples for Enantiomer Separations by Crystallization with TADDOLs. Besides the original TADDOL (from tartrate acetonide and PhMgX), Toda et al. [44] have often used the cyclopentanone- and cyclohexanone-derived analogs. The dynamic resolution (resolution with in-situ recychng) of 2-(2-methoxyethyl)cyclohexanone was reported by Tsunoda et al. The resolved compounds shown here are only a small selection from a large number of successful resolutions, which include alcohols, ethers, oxiranes, ketones, esters, lactones, anhydrides, imides, amines, aziridines, cyanohydrins, and sulfoxides. The yields given refer to the amount of guest compound isolated in the procedure given. Since we are not dealing with reactions (for which we use % es to indicate enantioselectivity with which the major enantiomer is formed), we use % ep (enantiomeric purity of the enantiomer isolated from the inclusion...

Another study " used a highly modified stilbene derivative (host M in Figure 22) as the host structure in a set of solid inclusion compounds containing a variety of small guest molecules (acetone, cyclopentanone, y-butyrolactone, dioxane, dimethylsulfoxide, pyridine, and A,A-dimethlyformamide), and it was observed that unidirectional cis trans photoisomerization occurs for the stilbene derivative. However, this one-way photoisomerization also occurs for the same stilbene derivative in the solid state (in the absence of any guest molecules), so the unidirectional nature of the photoisomerization reaction in this case is not dependent on the inclusion phenomenon, although it does provide an interesting point of comparison. 

Figure 22 Molecular structure of host M [cis-3,3 -bis(diphenylhydrox3raiethyl)stilbene]. Host M is able to undergo irrevCTsible isomerization in its inclusion compounds with the following guests acetone, cyclopentanone, y-butyrolactone, dioxane, dimethylsulfoxide, p3niduie, and Al,lV-dimethl3dbnnamide.

ABSTRACTii Cyci odeKtr i ns open great possi bi 1 i ti es for studying bath th66 crystal structure and the spectroscopic properties, in solution of the same compound In the present paper new inclusion compounds are studied. Two conformati onaly 1abi1e moleculbb (cyclopentanone,... 

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