The goal of this and two succeeding papers was to investigate the effects of rigid tetrahedral cores (such as adamantane) on the properties of aramid and poly (phenylene) dendrimers as well as dendrimers that form single molecule micelles. This paper deals with model compound studies dealing with generating tetrasubstituted derivatives of adamantane. A previously reported procedure (for making tetraphenyladamantane) using tert-butyl bromide-AlCL catalyzed arylation of 1-bromoadamantane was found not to be a general synthetic method for the preparation of other substituted adamantane derivatives. Adamantane derivatives with multiple phenyl substituents were isolated only when benzene and bromobenzene were used in the Friedel-Crafts reaction. Tetraphenyl-substituted adamantane derivatives were formed, however, by the traditional Friedel-Crafts arylation of 1,3,5,7-tetrabromoadamantane with bromobenzene and 1,3dibromobenzene. A lack of regioselectivity for these reactions (isolated mixtures of the meta/para isomers or ortho/meta isomers) was observed. Large quantities (50-100 g) of 1,3,5,7-tetraphenyladamantane (1) were prepared from 1-bromoadamantane using a slightly modified literature procedure. This organic insoluble compound was iodinated with [bis(trifluoroacetoxy)iodo]benzene to give the all-para-substituted compound, 5. Compound 5 was further reacted to give numerous derivatives and used as a core in the synthesis of first generation dendrimers.

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Tetrakis(4-iodophenyl)adamantane was reacted with 2-methyl-3-butyn-2-ol and phenylacetylene under Pd-catalyzed Heck coupling conditions to give the two corresponding tetraacetylene derivatives. Deprotection of the first gave the derivative with free terminal acetylenes. Thermal cure of both acetylene-containing monomers was monitored by FTIR. The cure products were then characterized by solid-state 13C cross-polarization magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy. This technique was combined with dipolar dephasing, in which resonances that are protonated are differentiated from those which are nonprotonated, to help clarify product composition. Both NMR and FTIR confirmed the presence of adamantane in the otherwise all-aromatic structures. TGA analysis indicated that these highly cross-linked materials began to degrade at ca. 450 and 490 °C, respectively, in air, confirming their excellent thermooxidative properties.

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