A novel phenol for use in convergent and divergent dendrimer synthesis: Access to core functionalisable trifurcate carbosilane dendrimers - The X-raycrystal 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 rea rrangement of the triallylsilyl fragment. Compound 1 can be used as a readi ly functionalisable dendrimer core unit and was applied in the divergent an d convergent synthesis of carbosilane dendrimers. An improved synthesis of chlorotriallylsilane, which is essential to the synthesis of 1, is also pre sented. Novel trifurcate carbosilane dendrimers, up to the second generatio n, have been synthesised by the divergent route starting from 1. These new materials have been fully characterised by a combination of NMR, IR and mas s spectroscopy (EI or MALDI-TOF), GPC and elemental analysis. Additionally, the use of 1 for the convergent synthesis of a carbosilane dendrimer is de monstrated by the formation of the dendron [1,3,5-tris(4-(triallylsilyl)phe nylester)benzene] (7). Compound 7 has been further characterised by single- crystal X-ray diffraction and represents not only the first structurally el ucidated aryl triester, but also the first structurally characterised trial lylorganosilane. The idealised (gas phase) structures of several of these n ew materials have been determined by means of MM2 molecular structure calcu lations. The largest carbosilane dendrimer( [G-2]) has a distorted spherica l structure. This is in contrast to dendron 7, which is shown to have an al most planar structure with respect to the central aromatic ring and the thr ee ester groups.