Saturated five-membered ring

Concentrate on the saturated five-membered ring part first. 

The H NMR data refer to at least one saturated five-membered ring moiety. The following compounds have been subjected to detailed study by 1H NMR spectroscopy. 

Figure 11.16 Structure of prostanoate, and three eicosanoids. Structurally, prostaglandins, thromboxanes and prostacyclins may be regarded as derivates of prostanoate, that is, they contain 20 carbon atoms and a saturated five membered ring (cyclopentane).

See Section 1.5.4. The saturated six membered rings are normally in a chair conformation whilst the saturated five membered rings have an envelope conformation. 

We discussed the conformation of some five-membered rings in Chapter 32 a saturated five-membered ring has a conformation variously called a half-chair or an envelope . It does look a bit like an opened envelope with one atom at the point of the flap, or it looks like most of (five-sixths rather than half ) a chair cyclohexane. 

The coupling constants of the Si-29 atoms and bridging CH2 protons cannot be clearly observed as the satellite on the left-hand side of the resonance line is superimposed upon the Si-methyl resonance of the saturated five-membered ring, so bearing in mind this restriction, the coupling constant is given as / =... 

For rings without nitrogen, the endings -ole and -olane are used to name partially- and fully-saturated five-membered rings. Representative examples are given in Figure 6. 

Sulpholane A dipolar aprotic solvent, which comprises a saturated five-membered ring containing one S02 group incorporated into a ring with four methylene groups. 

Tetrahydrofuran A saturated five-membered ring compound in which there is one oxygen atom and four carbon atoms. 

Saturated five-membered-ring molecules have two low-frequency out-of-plane ring vibrations and these modes may couple. Equation (3.33) is an appropriate two-... 

SATURATED FIVE-MEMBERED RING AZAHETEROCYCLIC SPIROPYRANS... 

Diborolanes (1) consist of fully saturated five-membered rings with two boron atoms in 1,2 or in... 

Gupta et al. have also made a compilation of IR data on 25 pyrrolizidine esters.88 Peaks at 740-760, 800-950, 960-980, and 1075-1130 cm"1 were assigned to ring deformation modes, and absorptions at 610, 750, and 965 cm -1 were attributed to the saturated five-membered ring. 

The H NMR data refer to at least one saturated five-membered ring moiety. 

A series of 5-hydroxymethyI-l,2-dihydropyrrolizines (26) have been prepared s by reaction of the parent dihydropyrrolizine derivative with formaldehyde and potassium carbonate. Analysis of the n.m.r. spectra of the products shows conclusively that the substituent enters position 5 in all cases examined, and that the saturated five-membered ring adopts the envelope conformation. 

The reason for this is most likely due to the fact that the saturated five-membered rings are very flexible due to pseudorotation and are involved in complex conformational equilibria in which the individual conformations were very difficult if not impossible to identify, whereas the pyranoid rings are rather stiff and consequently have much simpler conformational equilibria. 

Compounds containing at least one tin-oxygen bond in a saturated five-membered ring have a tendency to self-assemble by intermolecular tin-oxygen bonding. Such compounds include dioxastannolannes (a class of antitumor-active compounds)... 

A user-friendly Matlab program for the pseudorotation analysis of saturated five-membered ring systems based on Vhh couplings has been designed by Hendrickx and Martins. ... 

Saturated six-membered rings are not planar and their effective M—M—M angle is about 109.5°. Saturated five-membered rings are not quite planar so their ring angle is a little less than the pentagon angle of 108° (104° is used here). 

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