Reactions in Solids Under Irradiation

Silica-bonded A -propyl sulfamic acid (SBNPSA) is employed as a solid acid catalyst for the synthesis of spirooxindoles via three-component reaction in good yields and short reaction times in ethanol under irradiation MW conditions. Irradiation of the combination of isatin or acenaphthoquinone, an activated metltylene reagent, and 1,3-dicaiboityl compounds in the presence of catalytic SBNPSA was found to be a suitable and efficient method for the synthesis of the biologically important spirooxindoles (Schemes 3.4 and 3.5) [48]. 

The enormous amount of research at the interface between physical and structural chemistry has been expertly reviewed recently by Schmalzried in a book about chemical kinetics of solids (Schmalzried 1995), dealing with matters such as morphology and reactions at evolving interfaces, oxidation specifically, internal reactions (such as internal oxidation), reactions under irradiation, etc. 

Oxo-2,5-cyclohexadienylidene [83] was generated in solid argon at 9 K by irradiation of diazo compound [84] with visible light (A>495 nm) (Sander et al., 1988 Bucher and Sander, 1992 Bucher et al., 1992). The IR, UV, and esr spectra of [83] were in accord with a structure having a triplet state with one delocalized electron. In the IR spectrum of the carbene [83] the r (CO) mode was found at 1496 cm which indicates a bond order of the C—O bond considerably less than 2. The low-temperature reaction of carbene [83] with CO generated the keto-ketene [85]. Irradiation (A = 543 10 nm) of [83] led to its transformation into a very labile species, presumed to be [86], which rearranged back to [83] not only under UV or... 

Irradiation of (+ )-crystals of 96 with a 400 W high-pressure Hg-lamp, with occasional grinding with an agate mortar and pestle for 40 h at room temperature gave ( + )-97 of 93 % ee in 74 % yield. Irradiation of (—)-crystals of 96 under the same conditions gave (—)-97 of 93 % ec in 75% yield48. Purification to 100% ee can easily be achieved by recrystallization from benzene. Although the photochemical conversion of 96 into 97 on irradiation in the solid state has been reported, enantioselectivity of the reaction has not been discussed 441. 

In chemical syntheses under the action of microwave irradiation the most successful applications are necessarily found to be the use of solvent-free systems [6], In these systems, microwaves interact directly with the reagents and can, therefore, drive chemical reactions more efficiently. The possible acceleration of such reactions might be optimum, because they are not moderated or impeded by solvents. Reactions on solid mineral supports and, in turn, the interaction of microwaves with the reagents on the solid phase boundary, which can substantially increase the rate of the reactions, are of particular interest [7]. 

Numerous reactions in organic synthesis can be achieved under solid-liquid PTC and with microwave irradiation in the absence of solvent, generally under normal pressure in open vessels. Increased amounts of reactants can be used to ensure better compatibility between the in-depth penetrability of materials and the radiation wavelength. 

A ground mixture of iron(III) nitrate and HZSM-5 zeolite, termed zeofen , has also been used both, in dichloromethane solution and in solid state under MW irradiation conditions [101]. It has been suggested that the zeolite aids the reproducibility of the reaction but any other aluminosilicate support would probably be equally effective. Recent studies point out attractive alternatives that do not employ any of the solid supports in such oxidations with nitrate salts [102]. 

Either MA or MM processes drop under more general class of solid-state amorphization reactions, SSAR. Amorphization by irradiation of solids was observed yet in the era of study of materials for nuclear reactors. In 1962, Bloch [88] amorphized UgFe by exposing it to fluxes of nuclear fission fragments. Others obsawed amorphization... 

Re(N2)Cl(dppe)2] with [NO][Bp4] or NO gas. The latter reaction involves a faeile oxidation of NO to form nitrate as has been shown by the crystal structure of the produet [Re(NO)Cl-(dppe)2][N03]2. The eomplex eontains a linear NO " ligand. A very similar reaetion, that of [Re(N2)Cl(dppe)2] in THF with NO and Tl[Bp4] under irradiation with UV light, yields a yellow solid which has been assigned to the structure tra 5-[Re(NO)2(dppe)2][BF4] on the basis of elemental analysis and speetroseopie data. The compound readily reaets with aeids FIX (X = Bp4, Cl, HSO4) to afford tra x-[Re(NO)F(dppe)2], tra 5-[Re(NO)Cl(dppe)2], and trans-[Re(NO)(HS04)(dppe)2], respeetively. 

Fluorous phase modifications of the Stille reaction were shown by Curran et al. to be accelerated by microwave irradiation.10 Similarly, Hallberg et al. demonstrated that such irradiation gives remarkably fast solid-phase Suzuki reactions, in the generation of biaryl units.9 Their reaction involved the coupling of a tethered (Rink amide TentaGel) aryl iodide or bromide with several boronic acids under 45 W of irradiation at 2450 MHz in sealed... 

The authors of this book started working on chemical kinetics more than 10 years ago focusing on investigations of particular radiation - induced processes in solids and liquids. Condensed matter physics, however, treats point (radiation) defects as active particles whose individual characteristics define kinetics of possible processes and radiation properties of materials. A study of an ensemble of such particles (defects), especially if they are created in large concentrations under irradiation for a long time, has lead us to many-particle problems, common in statistical physics. However, the standard theory of diffusion-controlled reactions as developed by Smoluchowski... 

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