Adamantane ring

Despite these structural features, the adamantane ring system is not strain-free 142). Comparison of an estimated heat of formation for adamantane based on group increments derived from acyclic alkanes in completely skew-free conformations 142> with the experimentally determined value 143 indicates that adamantane is strained to the extent of 6.48 kcal/mole. 

Since the adamantane ring system is composed of three interlocking cyclohexane rings, all in the perfect chair conformation, /3-sub stituted adamanta-nones are also ideal models for establishing quantitative substituent contributions to the optical rotatory dispersion of cyclohexanones in the undisturbed chair form. A variety of optically active /3-equatorial and /3-axial substituted adamantanones have been synthesized 18°-184) and their circular dichroism determined 184-185) jji generai) axial polar substituents (C02R, Cl,... 

Treatment of l,3-dibromo-3,5-dibromomethyladamantane with zinc results in a double fragmentation of the adamantane ring 1,3,5,7-tetramethylenecyclo-octane is formed in high yield. Bromination of the product with bromine in carbon tetrachloride regenerates the starting material 3631. 

Conceptually similar a,a -annulations of ketone enamines have also been carried out with electrophilic alkenes containing a reactive allylic halogen, such as ethyl a-bromo-methylacrylate or dimethyl y-bromomesaconate318-320 (Scheme 156). An elegant one-pot synthesis of the adamantane ring system involving sequential double Stork and Dieckmann reactions has been developed by Stetter and Thomas321 (Scheme 157). Reaction of the bis-enamine 154 with ethyl a-bromomethylacrylate leads to the pentacy-clic system 155322 (Scheme 158). 

Figure 6-12. This adamantane derivative contains a benzene ring and a keto group that agree in stereochemistry, but discrepancies occur in the carboxylate and the adamantane ring. Of two molecules in the asymmetric unit of JUHMAA, this is molecule 1. JUHLUTIO—Ref. [21], JUHMAAIO—Ref. [22]...

The spiro-l,3,4-thiadiazoline 110 loses Ni at -45 °C to give the short-lived adamantanethione 5-methylide dipole 111. Interception of 111 by various acidic reagents has led to further fuctionalisation of the adamantane ring system, giving thio derivatives <01T145>. 

Sodium tetrahydridoborateltrifluoromethanesulfonic acid Adamantane ring by reductive skeletal rearrangement s. 44, 919... 

Zinc, sodium iodide, sodium carbonate Reductive fragmentation-type adamantane ring opening... 

Treatment of 3-methylenebicyclo[3.3.1]nonan-7-one with acids yields polymers with adamantane rings in the repeat units (151). 

Boiling compound 29 in liquid bromine for 4h also leads to formation of compound 49, but in higher yield. They were not able to add a bromine atom to the adamantane ring even when using catalysts (Lewis acids) conventionally used for difficult bromination reactions. Regardless of the reaction conditions, they could detect formation of only compound 49. They converted compound 49 to the acetoamino derivative via the Ritter reaction [45]. 

The exact mechanism of acetylene group thermal polymerization is still not clear. It is evident that the adamantane ring stays intact upon polymerization and contributes to the high thermal stability of the cured hydrocarbon networks. We hope to use C labeled monomers to further investigate cure mechanism details. 

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