Hervé Deleuze

Preparation and functionalization of (vinyl)polystyrene polyHIPE®.: Short routes to binding functional groups through a dimethylene spacer

Abstract This paper describes the preparation and post-functionalization of an emulsion-derived polymeric foam, called polyHIPE ® , bearing pendant vinyl functionalities. The large pores and large channels of polyHIPE allow liquids and solvents to be driven through the molded monolith at very low pressure. In the presence of a free-radical initiator, compounds such as HBr and thiols underwent an anti-Markovnikov addition to the residual vinyl groups. Other reactions such as hydroboration with BH 3 followed by hydrolysis with H 2 O 2 have also been investigated. In this paper, a comparison between two ways of functionalization has been made: a ‘batch’ method, corresponding to diffusion of reactants through the pores of small cubes of polymers, and a ‘continuous flow’ method, forcing reactants to flow through the interconnected porous structure by applied low pressure.

Preparation of LiBH4@carbon micro–macrocellular foams: tuning hydrogen release through varying microporosity

Microporous–macroporous carbononaceous monolith-type materials, prepared through a hard template method using silica as exo-templating matrices, have been impregnated with an etheric solution of LiBH4 to prepare LiBH4@carbon samples. It has been shown that the amorphous character of LiBH4 is largely favoured when developing the carbon microporosity (pores smaller than 2 nm) and that, as a consequence, the LiBH4 dehydrogenation is strongly enhanced at low temperatures. The onset temperature of dehydrogenation can be decreased to 200 °C and hydrogen capacity reaching 4.0 wt% is obtained at 300 °C with the carbon having the largest microporous volume, whereas the hydrogen release for bulk LiBH4 is negligible at the same temperature. It is suggested both from DSC and from pressure values reached upon hydrogen release that the enthalpy of the dehydrogenation reaction is strongly modified. In addition to some irreversible reactions with carbon surface groups (and even with the carbon matrix itself according to 11B MAS NMR spectroscopy, which reveals the formation of B–C bonds), the explanation for such modification could lie in the LiBH4 destabilization through confinement to the nanoscale range and associated amorphization. The above feature, where LiBH4 crystalline character is tuned through the imposed microporosity, can be considered as a highly promising approach to control the hydrogen release temperature of complex hydrides.

Polymer-supported titanates as catalysts for transesterification reactions

Abstract Polymer-supported titanates were prepared by covalent bonding of a trialkoxychlorotitane to a preformed macroporous poly(4-hydroxystyrene) resin. The reactivity and stability to recycling of the catalyst obtained were demonstrated in the catalysis of the transesterifications of methyl methacrylate with 2-ethylhexanol and ethyl butyrate with 1-dodecanol. A low leaching of titanium was observed during four successive uses of the resin as a transesterification catalyst.

Boronic ester as a linker system for solid phase synthesis

Abstract A method for attaching boronic acids to a macroporous polymer-supported 1,3-diol was developed. Chemical modifications of some polymer-bound arylboronic acids were realised using various reaction conditions. Trans-esterification gave new boronates in high purity while oxidative cleavage directly led to phenols.

Synthesis and functionalisation of polyHIPE® beads

Discrete spheroidal particles of interconnected microcellular foams were synthesised by suspension polymerisation of a high internal phase emulsion. These particles have been surface-grafted with functionalised macromolecular chains by controlled radical polymerisation using a covalently-bond TEMPO initiator.

Preparation and functionalization of (vinyl)polystyrene polyHIPE

Abstract This paper describes the preparation and post-functionalization of an emulsion-derived polymeric foam, called polyHIPE ® , bearing pendant vinyl functionalities. The large pores and large channels of polyHIPE allow liquids and solvents to be driven through the molded monolith at very low pressure. In the presence of a free-radical initiator, compounds such as HBr and thiols underwent an anti-Markovnikov addition to the residual vinyl groups. Other reactions such as hydroboration with BH 3 followed by hydrolysis with H 2 O 2 have also been investigated. In this paper, a comparison between two ways of functionalization has been made: a ‘batch’ method, corresponding to diffusion of reactants through the pores of small cubes of polymers, and a ‘continuous flow’ method, forcing reactants to flow through the interconnected porous structure by applied low pressure.

Syntheses and characterization of highly mesoporous crystalline TiO2 macrocellular foams

Titanium dioxide open-cell macro-cellular foams have been generated with emphasis toward controlling macro-, meso- and microstructures thus reaching hierarchically organized inorganic architectures. At the macroscopic length scale a non-static air–liquid foam strategy allows strong control over the open-cell morphologies. At the meso- and/or nanoscopic length scales various mesogenic templates or latex colloids have been used to promote mesoporosity. Among the strategies in use, a Pluronic copolymer P-123 combined with tetradecyltrimethylammonium bromide induce vermicular-like mesoporosity associated with a specific surface area around 400 m2 g−1. At the microscopic length scale, upon the use of specific thermal treatment, either monophasic anatase, biphasic anatase–rutile or monophasic rutile allotropic forms are obtained.

Enzymes in organic synthesis VII: enzymatic acylation of amines

Abstract Lipases and esterases catalyze amide synthesis from primary amines in the presence of various esters. Lipase SP 382 exhibited a very high activity and specificity.

Synthesis of porous supports containing N-(p-hydroxyphenyl)- or N-(3-4-dihydroxybenzyl) maleimide-anchored titanates and application as catalysts for transesterification and epoxidation reactions

N-(p-acetoxyphenyl)maleimide and N-(piperonyl)maleimide were polymerized in suspension to give macroporous supports. After deprotection of the p-acetoxyphenyl and of the piperonyl groups, resins with pendant p-hydroxyphenyl and catechol units were obtained. These results illustrate a very easy and convenient way to synthesize phenol and catechol containing supports. Polymer-supported transesterification and epoxidation catalysts were obtained by immobilization of Ti(OiPr)4 and TiCl4. These catalysts were efficient for both reactions and could be recycled several times although some titanium leaching (≤ 20%) was observed in each case.

Preparation and reactivity of a macroporous polymer-supported organotin hydride catalyst

Abstract Macroporous beads bearing organotin moieties have been synthesized by suspension copolymerization of a convenient organotin monomer with styrene and a crosslinking agent in the presence of a porogen. The influence of the nature and amount of the crosslinking agent on the properties of the resulting materials are discussed in terms of their permanent porosity, their swelling in solvents and their average pore diameter. The catalytic activity of the polymer-supported organotin chloride obtained has been tested in the reduction of 1-bromoadamantane by the sodium tetrahydroborate. The results are comparable with those observed with soluble tributyltin hydride. The good stability of the grafted tin functionality was demonstrated by performing several successive batches with constant activity without the need of a regeneration step.