Organometallic compounds substitution reactions

We prepared numerous new organosilicon polymers using the described a,co-bis[(trifluoromethyl)-sulfonyloxy]-substituted organosilicon derivatives as electrophilic starting materials [13, 14]. The dinucleophilic reactants were either organic or organometallic compounds. The reactions of [phenylene-1,4-bis(dimethylsilanediyl)]bis(trifluoromethanesulfonate) with six dinucleophiles in Scheme 1 illustrate the potential of this method. We could confirm the formation of the polymers at low temperature, in short reaction times, and with high yields. 

Prior to the development of methods for caiTving out the direct reaction of fomialdehyde vdth acetydene or monosubstituted acetylenes (page 237), the only satisfactory procedime for preparing acetylenic alcohols from formaldehyde involved the intennediate preparation of organometallic compounds. Substituted pi Opargyl alcohols are obtained in yields of 70 per cent or better by reaction of monosubstituted acetylenic Grignard compounds with gaseous formaldehyde ... 

Another such effect is the intervention of cyclic transition states in reactions of organometallic compounds (Section II, B, 5) with azines or in intramolecular nucleophilic substitutions (Section II, F). 

Mechanistically the reaction can be divided into two steps. Initially the alkyl halide 1 reacts with sodium to give an organometallic species 3, that can be isolated in many cases. In a second step the carbanionic R of the organometallic compound 3 acts as nucleophile in a substitution reaction with alkyl halide 1 to replace the halide ... 

Reutov, O. A., The mechanisms of the substitution reactions of non-transition metal organometallic compounds, J. Organomet. Chem. 100, 219 (1975). 

In addition to trialkylboranes, various alkoxyboron compounds have prominent roles in synthesis. Some of these, such as catecholboranes (see. p. 340) can be made by hydroboration. Others are made by organometallic or related substitution reactions. Alkoxyboron compounds are usually named as esters. Compounds with one alkoxy group are esters of borinic acids and are called borinates. Compounds with two alkoxy groups are called boronates. Trialkoxyboron compounds are borates. 

In some reactions of carbanions or organometallic compounds with very weak acids the base has a choice of protons and can give more than one salt. An example is the nuclear metallation of a substituted benzene in which the product may be oriented ortho, meta, or para. The actual results of a few such reactions are shown in Table XII. 

Substitution reactions on phosphorus-halogen compounds using organometallics and related reagents... 

Non-heteroatom-substituted carbene complexes play a key role both as reagents and catalysts in organic synthesis and as intermediates in the preparation of other organometallic compounds. However, discussion of applications in inorganic synthesis would surpass the scope of this book. Here the focus will be on those reactions which lead to metal-free compounds and hence are particularly relevant to the organic chemist. 

The polarity of carbon-halogen bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Nucleophilic substitution reactions are categorised into and on the basis of their kinetic properties. Chirality has a profound role in understanding the reaction mechanisms of Sj l and Sj 2 reactions. Sj 2 reactions of chiral all l halides are characterised by the inversion of configuration while Sj l reactions are characterised by racemisation. 

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