A novel phenol for use in convergent and divergent dendrimer synthesis:: Access to core functionalisable trifurcate carbosilane dendrimers -: The X-ray crystal structure of [1,3,5-tris{4-(triallylsilyl) phenylester)benzene

The organosilane 4-(triallylsilyl)phenol (1) was synthesised in high yield by two different routes starting from two different silyl-protected phenols. One of these routes involves the first example of a retro-[1,4]-Brook rearrangement of the triallylsilyl fragment. Compound 1 can be used as a readily functionalisable dendrimer core unit and was applied in the divergent and convergent synthesis of carbosilane dendrimers. An improved synthesis of chlorotriallylsilane, which is essential to the synthesis of 1, is also presented. Novel trifurcate carbosilane dendrimers, up to the second generation, have been synthesised by the divergent route starting from 1. These new materials have been fully characterised by a combination of NMR, IR and mass spectroscopy (EI or MALDI-TOF), GPC and elemental analysis. Additionally, the use of 1 for the convergent synthesis of a carbosilane dendrimer is demonstrated by the formation of the dendron [1,3,5-tris(4-(triallylsilyl)phenylester)benzene] (7). Compound 7 has been further characterised by single-crystal X-ray diffraction and represents not only the first structurally elucidated aryl triester, but also the first structurally characterised triallylorganosilane. The idealised (gas phase) structures of several of these new materials have been determined by means of MM2 molecular structure calculations. The largest carbosilane dendrimer( [G-2]) has a distorted spherical structure. This is in contrast to dendron 7, which is shown to have an almost planar structure with respect to the central aromatic ring and the three ester groups.