Anion assistance, solid state

A first example that illustrated this concept of directing a photochemical [2 + 2] dimerisation in the solid state was reported by Ito and Sheffer/ in which diamines were used to form salts from a,p unsaturated carboxylic acids. The transference of the acidic proton in carbo g lic acids by strong base leads to the molecular salts where photodimerisation occurs between two anionic moieties. For example, two cinnamate anions are positioned in parallel form suitable for a [2 -I- 2] photocycloaddition using ethylenediamine via charge-assisted hydrogen bonds 0 ). 

Ring-opening polymerization (ROP) has seen broad utility for synthesizing main-chain organometallic polymers. Initially reported by Rauchfuss [9], and thoroughly developed by Manners and coworkers [10], the transformation from 10 to 11 (Schane 1.4) has been optimized to include various conditions for polymerization such as thermal, anionic, photo, and metal-mediated polymerizations Both solution and solid-state polymerization have also been reported. Molecular weights on the order of 10 Da have been achieved and the ability to prepare monomers of varying functionahty has assisted... 

More recently, Normant and coworkers have reported catalysis of the reaction between potassium acetate and benzyl chloride in acetonitrile by polyamines in a two phase system [28]. It seems likely that the catalytic activity reported by Normant et al. is related to the earlier alkylations discussed above. The authors state in their communication, however, their finding that ... quaternary ammonium salts corresponding to the diamines do not activate anions under the experimental conditions used. . In the reaction referred to here, it seems likely that the diamines are playing a dual role. The diamines are probably assisting in the solubilization of the solid (and relatively insoluble) potassium acetate by chelation of the potassium cation and the homogeneous reaction is then probably catalyzed by the quaternary ion formed in situ. That the catalytic activity of the amine depends on the hardness of the cation (the harder the cation, the less catalytic activity) [28] seems to accord with this interpretation although lattice energy differences cannot be discounted. 

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