Cisoid arrangement

It is interesting to note that 4-aminopent-3-en-2-one (85), which is held in a cisoid arrangement by hydrogen bonding, gives the product 86, which is stable in anhydrous solvent, but which cyclizes under the influence of water to give methyl 2-methyl-5-oxo-4-(2-oxopropylidene)-2-pyrroline-3-carboxylate (87). 

It is important that the five carbon atoms making up the 77-pentadienyl system have the cisoid arrangement. Thus fails to abstract a hydride... 

The ultraviolet spectra 27,28 exhibit, in agreement with the general postulate of Braude et al.2%-30 a bathoehromic shift to 225-235 m/j. caused by the auxochromic action of the nitrogen-free electron pair. This shift is approximately the same as that caused by introduction of a conjugated double bond, and is increased by further conjugation with other multiple bonds, e.g. in diene-amines prepared from A -3-oxosteroids.31,32 Spectral maxima (at 280-285 mfi, e 19,000-26,000) point to the conjugation of three mobile electron pairs but cannot decide the position of the double bonds the molecular extinction coefficient indicates a transoid (5) rather than cisoid arrangement (e.g. 6).33... 

The results clearly indicate that the volume of activation is more negative for higher sterically hindered reactions. This means that the high-pressure approach should be especially effective in cases where highly hindered amines are quatemized. Indeed, the high-pressure reaction of methyl iodide with a-isolupanine (37) which is characterized by the cisoid arrangement of the N-atoms, leads in 99% yield to the respective methiodide 38 (Scheme 8). It is noteworthy to mention that the quatemiza-... 

The dissymmetic (C2 symmetry) dihydrodinaphthothiepin 43 and related bridged diaryl derivatives are of interest because the stereoisomers can be separated (atropisomers) and have potential applications as chiral reagents. An X-ray crystal study of compound 43 shows that it has a cisoid arrangement around the biaryl bond with an interplane angle of 66.1 <1995T787, CHEC-III(13.03.3.1)102>. 

A possible mode of formation of 6 could be via the condensation of two cyclic intermediates with cisoid arrangements of Si-X groups (X = Cl or OH), e.g. 9. 

This anomalously rapid reaction was considered to occur because the double bonds are held in a cisoid arrangement by the structure of the ring. 

In fixe formation of the perchlorate salt, protonation takes place initially at N-1 and the cisoidal arrangement of the monosalt is thus stabilised by means of an intramolecular hydrogen bond. This cisoidal arrangement is fiuther stabilised by the co-planarity of the enamine double bond, the phenyl and the N-16 lone pair whose delocalisation further reduces repulsion between N-1 andN-16, Fig. (29). 

All the reduced 2- and 15-substituted sparteine derivatives have been shown to exist in a transoidal form in solution and to crystallise as monoperchlorate salts in a cisoidal arrangement, in close resemblance to sparteine. Protonation of N-16 or N-1, in 2- and 15-substituted derivatives, respectively, leads to the formation of an intramolecular hydrogen bond which stabilises the cisoidal salt. These results were later supported by the detailed IR and C NMR analysis of 2-(p-tolyl)-sparteine and its monoperchlorate salt [198]. 

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