Modular Construction of Dendritic Carbosilanes. Organization of Dendrimer Connectivity around Bifunctional Precursors That Are Adapted for Sequential Convergent and Divergent Propagative Steps

Abstract

Regiospecific hydrosilylation of 1-bromo-4-(prop-2-enyl)benzene offers an efficient route to molecular building block precursors that can accommodate sequential divergent and convergent steps for dendritic extension, establishing a modular methodology for assembly and organization of connectivity used for synthesis of modified carbosilane dendrimers including 14.

Introduction of per(fluoroorganosilyl) peripheries into carbosilane dendrimers and related core-functionalized monodendrons gives rise to anomalous hydrodynamic and viscosimetric behavior

“…Dendrimer 4 functionalization to prefabricate a suitable hyperbranched subunit, followed by binding of the latter to an appropriate support, is a potentially 5 versatile way of developing such surface coverage; but despite its recent rapid rate of advancement, 4,6 dendrimer chemistry so far offers only a very limited range 729 of fluorinated prototypes. Our interest 10,11 in carbosilane 8212 dendrimers as chemically passive frameworks has led us to explore routes to such species in which a fluorinated organic group is bound to each peripheral silicon atom directly, avoiding conjunction through a heteroatom (O or S) as has been reported elsewhere by others. 8,9 We show that by using polyfluoroorgano-substituted silanes in a final convergent step, peripheral modification of allyl-terminated carbosilane dendrimers is possible; and more particularly that, by adaptation of a modular approach 11 to carbosilane monodendrons, members of a family to [G-3] of core p-bromophenyl-functionalized analogues may be isolated in high yield.…”

“…Our interest 10,11 in carbosilane 8212 dendrimers as chemically passive frameworks has led us to explore routes to such species in which a fluorinated organic group is bound to each peripheral silicon atom directly, avoiding conjunction through a heteroatom (O or S) as has been reported elsewhere by others. 8,9 We show that by using polyfluoroorgano-substituted silanes in a final convergent step, peripheral modification of allyl-terminated carbosilane dendrimers is possible; and more particularly that, by adaptation of a modular approach 11 to carbosilane monodendrons, members of a family to [G-3] of core p-bromophenyl-functionalized analogues may be isolated in high yield. These latter products, in which the unique core functionality can be used for further chemistry including polymer or surface attachment, have been fully characterized by size exclusion chromatography (SEC) and viscosimetry as well as by spectroscopic and analytical data.…”

“…Construction of analogues that can serve as fluorous mesomolecular building blocks may be accomplished, however, by similarly adding the silanes 1a,b across the peripheral allyl groups of the p-bromophenylsubstituted trifurcate monodendrons described elsewhere. 11 This routine has been used to synthesize the new monodendrons 5a,b-7a,b, (Scheme 1) which proved to be much easier to purify on flash silica gel than their dendrimer counterparts: like the latter, they remain fluid to [G-3] (glassy transition temperatures T g / 0 C: 266, 5a; 258, 5b; 265, 6a; 253, 6b; 259, 7a; 253, 7b) and have likewise been fully characterized. † Prospective use in 11 modular synthesis led us to investigate the physical behavior of these compounds in more detail, using SEC and viscosity measurements.…”

“…11 This routine has been used to synthesize the new monodendrons 5a,b-7a,b, (Scheme 1) which proved to be much easier to purify on flash silica gel than their dendrimer counterparts: like the latter, they remain fluid to [G-3] (glassy transition temperatures T g / 0 C: 266, 5a; 258, 5b; 265, 6a; 253, 6b; 259, 7a; 253, 7b) and have likewise been fully characterized. † Prospective use in 11 modular synthesis led us to investigate the physical behavior of these compounds in more detail, using SEC and viscosity measurements.…”

Synthesis of Small Carboranylsilane Dendrons as Scaffolds for Multiple Functionalizations

“…Likewise, the functionalization has also been achieved by the hydrosilylation reaction of chlorovinylstyrene with 9 in the same conditions to give compound 11 (99%) (Scheme ). Compounds 10 and 11 provide a means of activation of dendrons for further reactions, such as transition-metal η 6 -arene complexes or coupling agents for Suzuki cross-coupling reactions, respectively.

2 Preparation of 11 by Hydrosilylation of Chlorovinylstyrene with Compound 9

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