And propellanes

Figure 1. Representative linear, angular, and propellane triquinane natural products.

The compounds of this series of fused (5 5 5) systems of three five-membered rings so far encountered may logically be divided into the following three distinct classes (1) linearly fused (5 5 5) systems, (2) angularly fused (5 5 5) systems, and (3) spiro-fused (5 5 5) systems. In addition to these three distinct classes, there are other compounds reported bearing bridged and propellane moities which are classified under the heading miscellaneous . 

To be quite formal about the connection between spirans and propellanes an interesting pathway may be cited, although admittedly, it is farfetched. 

With this new notation, we can now consider briefly the retrosynthetic analysis of some triquinanes and propellanes discussed by Curran [29]. 

Inasmuch as both types of tetrazole derivs(when they contain one or two alkyls of low mw) are high nitrogen compds, they may be of interest as components of explosives and propellan ts... 

An elegant application of this photocycloaddition in the field of triquinane synthesis has been reported by Reddy and Rawal [160]. The initially formed oxetane 163, formed from the Diels-Alder adduct 162, is easily cleaved reductively (by use of LiDBB = lithium di-/er -butyl-biphenylide) to give 164. This approach was also used for the construction of structurally diverse di- and (propellane-type as well as linear or angular anellated) triquinanes [161]. The classic linear triquinane hirsutene is also available via this route [162]. Star-like molecules like the tiene 167 are available via a sequence of intramolecular photocycloaddition (from the 1,3-cyclohexadiene/acylallene adduct 165) and oxetane (166) ring-opening (Sch. 58) [163]. Further examples of intramolecular... 

This chapter will cover eliminations of HX, X2 and XSiR3 (X = halogen) which lead to the formation of cyclopropenes, bicyclobutanes and propellanes and aspects of other elimi-... 

IJPropellane and many of its derivatives are liquids at ambient temperature. Some derivatives such as Im, Iw and Iz melt at higher temperatures, 60-62 °C, 70-73 ° and 171 °C (dec), respectively. The parent propellane itself melts at about -11°C, and propellanes Ih and lo are solids at -78... 

Synthesis of a Stable Iminium Salt and Propellane Derivatives [43]. 210... 

In addition to these two distinct classes, there are more compounds reported bearing spiro and propellane moieties which are classified under the heading miscellaneous . 

Xylylene dibromide and c/j-l,4-dichloro-2-butene react similarly with ethanedithiol <64ZC302>, while alkylation of ethanedithiol with tetrabromides under high dilution conditions afford bis(dithiocin) (185) (Equation (57)) and propellane (186) (Equation (58)) (also preparable by carbene addition to (185)) in 57% and 15% yields, respectively <85M229>. 

Fig. 2.1 Planar- (a), pyramidal- (b) and propellane-type (c) carbon atoms...

The carbon atoms not at the ends of the stack have a half-planar or bntterfly-type disposition of their fonr bonds (Fig. 12.2). This makes them members of the unconventional non-tetrahedral assortment of tetracoordinate carbons to which also belong planar, pyramidal, and propellane (umbrella) carbon (Fig. 12.2 references to these carbon stereochemistries and to half-planar carbon in organometallic compounds, are given in [1]). Thns they excite the same kind of curiosity as that engendered by the planar carbon of Chapter 1 and the pyramidal carbon of Chapter 2. 

Fig. 12.2 The half-planar or butterfly stereochemistry of carbon atoms in polyprismanes. Besides this and the normal tetrahedral, other conceivable stereochemistries for carbon are the planar (Chapter 1), pyramidal (Chapter 2), and propellane. See refs, in [1]...

To discuss and compare theoretically defined strain energies with those defined in terms of the experimental heats of formation for the cyclic, bicyclic and propellane molecules, we shall define group energies in the same manner as is done using the experimental heats of formation except that they will not be referenced to the standard states of the elements. The strain energy of a given group in a molecule is obtained by... 

This title is given here to a varied collection of polycyclic ring systems extending adamantanes and propellanes which are separately discussed. There is no particular order of presentation. 

As well as cubanes, other small aliphatic ring systems, such as cyclopropanes, cyclobutanes, azetidines and propellanes, are potentially interesting candidates for incorporation into monomer collections as they are often sought as variants of methyl, isopropyl and te/t-butyl groups. 

It should be noted that reviews covering specific areas of this chapter have appeared periodically [5, 6], dealing mostly with their authors findings on the polymerization of bicyclobutanes [7-9], cyclopropanes [1,3,10-12] and propellanes [13-16]. These reviews are highly recommended as a further source of information, not only for the polymerization of monomers but also for the properties of the polymers thus obtained. 

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