Through Salt Eliminations

The Wiberg -type silenes like 92, available through salt elimination reactions from 93, react with nonenolisable aldehydes, ketones and the corresponding imino derivatives to give in a first step donor adducts 9459, which are then transformed to the [2 + 2] and [2 + 4] cycloadducts 95 and 96, respectively (equation 21)60-62. These cycloadducts may liberate the silene 92 upon heating and it can be trapped by suitable reagents. 

Photo chemically induced borylene transfer has already been discussed as a valuable synthetic method for the generation of terminal borylene complexes not accessible through salt elimination reactions (vide supra). Photolysis of [(CO)5W=BN(SiMe3)2] (2) in the presence of [( 5-C5H5)Re(CO)3] yielded the... 

Upon addition of a base—triethylamine is often used—the sulfonium salt 7 is deprotonated to give a sulfonium ylide 8. The latter decomposes into the carbonyl compound 2 and dimethyl sulfide 9 through /3-elimination via a cyclic transition state. 

Limitations common to both salt elimination methods 1 and 2 are (a) the required product may be difficult to separate from the alkali metal halide, (b) reactions are best carried out in the solvent (usually an ether) in which the initial alkali metal derivative is prepared, (c) difficulties may arise through metal-halogen exchange (207), and (d) the range of starting anions is limited [e.g., X3Si compounds are only readily formed when X = H or Ar,... 

Disubstituted tetrazoles are conveniently prepared from acyl hydrazines (98) and diazonium salts.166 The reaction proceeds through the intermediate tetrazenes (99) followed by cyclization to the tetrazole (100) (Scheme 13). The intermediate can be isolated under mildly basic conditions. Symmetrically 1,2-diacylated hydrazines yield 1-substituted tetrazoles through the elimination of one of the acyl groups.166 - 168 Diformyl-hydrazine is a very convenient starting material for 1-substituted tetrazoles.166, Unsymmetrically 1,2-diacylated hydrazine usually results in mixtures.169... 

Developed by Summit Research Corp. (Santa Fe, Nuevo Mejico, USA), the reactor is made with a porous Inconel interior wall. Through it, a wall cleaning fluid circulates, to avoid salts encrusting onto it. Part of the reactor effluent can be used as cleaning fluid at the end of the salts elimination. In this way salts deposition on the wall is avoided and there is a gain from feed preheating [14]. This reactor is sketched in Fig. 9.4-7. 

Dehydrations of crystalline hydrates do not invariably yield the anhydrous salt as a product through the elimination of water, as exemplified by the dehydration of MgCl2.2H20 [116] ... 

Another plausible mechanism through which these species could be prepared is a salt elimination or metathesis reaction, in which component parts of different molecules are exchanged to yield new structures. The prerequisite for the formation of Sn(II) heterometallic complexes is that the two or more combining metals must have nearly the same electropositive character as that of tin and also have the capability to enhance their coordination sphere upon complexation under suitable reaction conditions. 

The easiest approach to prepare Sn(II) heterometallic molecules is the substitution of an anionic ligand by a suitable halo-alkoxometallate ligand through the salt elimination mechanism. " ... 

It is well known that thermal polycondensation of ha-logenoacetates leads to polyglycolide through the elimination of a metal halide salt, which can be considered as the driving force of the polycondensation reaction. The method has recently applied to get PEAs constituted by an alternating sequence of glycolic acid and co-amino acid units (Figure 8.3a) [20-24]. Monomers be easily synthesized by the reaction of chloroacetyl chloride with the appropriated (o-amino acid and by a subsequent neutralization with a... 

Many polar solvents, e g., ethers, possess lone pairs and are therefore capable of acting as dative ligands to RE centers. Many organometallic RE complexes are either prepared in ethers to aid the salt-elimination reactions employed in their synthesis through provision of a polar reaction medium or utilize RE halides which incorporate ethers to aid then-solubility. Thus, if coordinated organometallic ligands are not... 

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