Gas-solid halogenation

The chlorine adduct to the tetrasubstituted exocyclic double bond in 108 is quantitatively obtained by gas-solid reaction [27]. Conversely, related trisub-stituted double bonds lose HX after the gas-solid halogen addition such as in the reactions of 110 and 112 that give 111 and 113,respectively [28] (Scheme 12). The completion of these solid-state eliminations (Sect. 11) is faster at 100 °C. The product 113 is an interesting substrate for the synthesis of orotic acids. Furthermore, the production of 116 from solid 114 and chlorine gas proceeds with 100% yield via the intermediate adduct 115 [58,60-61] (Scheme 12). 

Table I. Gas-Solid Halogenation and Hydro-halogenation of trans-Cinnamic Acid in the Cavity of Cyclodextrin Complexes or without...

ABSTRACT The gas-solid halogenation and hydrohalogenation using micro-crystalline cyclodextrin complexes are found to be efficient for production of the optical active halides of ethyl trans-cinnamate in moderate optical yields On exposure to HBr at 2QOC for 15-20 hr, the cinnamate in solid a- and S-cyclodextrin complexes yields ethyl R-(+)-3-bromo-3-phenylpropanoate in 46% e.e., and S-(-)-enantiomer in 31% e.e., respectively. No addition nor substitution products are obtained with HCl vapor at 0-50°C for 15-65 hr. Bromination of the B-cyclodextrin complex results in the formation of optical active ethyl erz/t/zrc>-2,3-dibromo-3-phenylpropanoate, while chlorination gives the optical active mixture of trans and cis addition products, ethyl erythro- and threo-2,3-di-chloro-3-phenylpropanoates in 60-80% yields. Mechanism of chiral induction in the present gas-solid reaction has been proposed on the basis of the crystal structure of the complex. 

The gas-solid halogenation of styrene 1 in the crystalline CD complexes produced 344... 

Fig. 3. Products from the gas-solid halogenation and hydrohalogenation of styrene in the crystalline cyclodextrin complexes.

M. Giihr, in Coherent Dynamics of Halogen Molecules in Rare Gas Solids, ed. by S. De Silvestri, G. Cerullo, G. Lanzani. Coherent Vibrational Dynamics (CRC, Boca Raton, 2007), p. 173... 

Keywords cinnamic acid, stilbene, halogenation, addition, gas-solid reaction... 

Keywords 1,1-bisarylethylene, triphenylethylene, halogenation, stilbene, elimination, gas-solid reaction, l-halogeno-2,2-diarylethene, l-halogeno-l,2,2-triphe-nylethene... 

In general, the methods of preparation can be divided into two classes reactions between solid halides or polyhalides and gaseous halogens or interhalogens, and reactions of the same type in an appropriate solvent. The conditions of the gas-solid reactions have been thoroughly investigated by Cremer and Duncan.2 Their conclusions can be summarized as follows. 

A nickel complex fixed to polystyrene by means of Ni-C through oxidative addition of halogenated polystyrene to Ni(0)-tetra(triphenylphos-phine) [261]. The catalyst was synthesized to an approximate degree of polymerization of 1100 in toluene solution at room temperature in the presence of nitrogen. It was found that the obtained complex was highly active during C2H4-dimerization reactions conducted in the presence of catalyst-toluene suspensions as well as in the gas-solid phase. It was shown that the solvent affects catalyst selectivity. Selectivity was lower in the gas-solid system, and considerable quantities of hexenes and octenes were formed. 

Without additional reagents Gas-solid phase halogenation w.a.r. H Hal... 

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