Pinacolone crystal structure

Seebach, Dunitz and coworkers reported, in 1981226, the first crystal structures of lithium enolates of simple ketones, obtained in THF from pinacolone (3,3-dimethyl-2-butanone) and cyclopentanone. Both were arranged as tetrasolvated cubic tetramers, one THF molecule capping each lithium cation (Scheme 58A). Note that pinacolone enolate can also be crystallized, from heptane at — 20 °C, as a prismatic unsolvated hexamer exhibiting an approximate S6 symmetry and six slight it-cation interactions227,228 (Scheme 58B) or as a dimer in the presence of 2 molecules of TriMEDA29. Similarly,... 

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. 

The facile reactions of TiCl3(OPr ), with a variety of O and N donors gave octahedral adducts.392 In the case of pinacolone (OC(Me)(But)) a 1 2 adduct was formed and exchange of free and bound pinacolone was shown to proceed via a dissociative mechanism. An X-ray crystal structure established the dimeric nature of (M iCl2(//-Cl)(0C(Me)(But)))2()7-02C6I IyMe) (42).393 Other dimeric derivatives of TiCl3(OPr ) have also been described.94,3... 

The successive replacement of the enolate by aldolate moieties en route from an enolate tetramer to an aldolate tetramer might involve severe reconstruction of the skeleton. Thus, a mixture of pinacolone, its lithium aldolate with pivalaldehyde, and the enolized aldolate dianion was recently reported to cocrystallize in a 1 1 3 ratio as a heptalithium cage compound missing any cube-shaped unit [15]. Rather complex crystal structures aldolate-enolate aggregates were also found for calcium enolates [8b]. 

A triple anion complex containing enolate, amide, and halide functionalities can be isolated from the mixture of n-butyl bromide, hexamethyldisilazane, TMEDA, Bu Li and pinacolone (Bu COMe). The resulting solution of LiBr, LiN(SiMc3)2, LiOC(Bu )=CH2, and TMEDA produces crystals of Li4(/.t4-Br)( u-OC(Bu )=CH2)2(M-N(SiMe3)2)(TMEDA)2, which, instead of forming a ladder-type structure, consists of a planar butterfly of four lithium atoms bonded to a //4-Br the stability of this arrangement has been studied with semi-empirical (PM3) and ab initio HE/ LANL2DZ computations. ... 

The pinacolone enolate residue crystallizes as a dimer with solvation by N,lV,lV -trimethylethylene-diamine (TriMEDA) as indicated in formula (141). In this structure the NH hydrogen on the secondary amine is relatively close to the terminal carbon of the enolate residue, i.e. NH—C=C is 2.60 A. This... 

Dihydrochloride, C HjjCIjNjO, Crystals from ethanol, dec 272-275. Soluble in water-Note Formerly a pinacolone structure was assigned to ampheoone B l,2-Bis[p-aminophenylJ-2-methyl-Tpro-... 

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