Organic halides analogous

The first purposeful use of ATRA in polymer synthesis was in the production of telomers.26j In this early work, comparatively poor control over the polymerization was achieved and little attempt was made to explore the wider utility of the process. Some analogies may also be drawn with the work of Bamford et al, and others on transition metal/organic halide redox initiation (Sections 3.3,5.1 and 7.6.2).2M... 

The reaction between triorganotin hydrides and organic halides is known since 1957 68). Analogous reactions have been described for chiral triorganosilicon69) and -germanium 70) hydrides, which are stereoselective. It is well known that they proceed via the triorganometal radical, which can also be formed photochemically from metallated ketones 71). 

This means that when we prepare Grignard reagents, we are effectively limited to alkyl halides or tro analogous organic halides containing C=C bonds, internal triple bonds, ether linkages, and -NR2 groups. 

In all of the systems so far investigated the aquation rate has been found to be pH independent in alkaline solution, at least up to 0.1MOH ", the largest concentration investigated. It may be noted that this behavior is entirely analogous to that of trityl chloride and other organic halides which undergo solvolysis by well established Svl mechsnisms. (S)... 

Another approach, recently described, consists in the electrochemical preparation of a very active zinc with the use of a mediator3. This zinc is able to react with low reactive organic halides. This electrochemical process is analogous to the chemical reaction developed by Rieke in which the naphthalene anion radical is used to activate metals such as zinc4. 

The first borinate-transition metal complex to be prepared was actually the first known derivative of borin. Bis(cyclopentadienide)cobalt (94) reacts with organic halides and was analogously found to react with boron halides in a redox reaction to give (95), followed by an insertion to yield (cyclopentadienide)(borinato)cobalt (97) (72CB3413). The product composition depends on the ratio of reactants. Compound (97) is the main product (80% yield when R = Ph, X = Br) when the molar ratio between (94) and the boron halide is 2.5 1. A second and slower insertion occurs to give (28) when (97) is treated with another equivalent of the boron halide (Scheme 13). Compounds (28), (29) and (97) have one electron more than predicted by the 187r-electron rule for transition metal complexes. They are red in colour and, of course, paramagnetic. The mixed complexes (97) are thermally labile, in contrast to (28) and (29), which can be heated to 180 °C and sublimed at 90 °C. Their ionization potentials are low and the complexes are sensitive to air. 

Analogous cyclic amines can also be prepared by aminomercuration-demercuration of unsaturated organic halides (equation 155).208... 

Halohydrocarbons with labile bromine atom react even more easily. On the other hand, organic halides with less labile halogen atoms require more drastic reaction conditions, and sometimes even the application of pressure. In its entirety the reaction is a useful method for synthesis of organotrichlorogermanes. There are no analogous reactions in the chemistry of chloroform and trichlorosilane and the logical explanation of the phenomena can be found in the concept of HGeCl3 superacidity. 

A variety of functionalised organic halides have been found to be compatible with the Sml2-mediated Barbier and Grignard reactions. For example, ben-zyloxymethyl chloride can be used in conjunction with Sml2 for the alkoxy-methylation of ketones.120 This addition has been found to work well even for hindered ketones such as 101, an intermediate in White s 1987 approach to 2-desoxystemodinone (Scheme 5.70).121 It is important to note that, in contrast to analogous organometallics, decomposition via a-elimination is not observed. 

Subsequently, kinetic studies reported by Whitesides and collaborators [81] provided further support for the view that the rate-determining step in formation of alkyl Grignard reagents involves electron transfer from the metal surface. The kinetics of the reaction of an organic halide RjX with magnesium were described by Eq. (3), in which S g accounted for the characteristics of magnesium surface that influence the rate, and an analogous... 

Stereochemical observations also support the analogy between electrochemical reactions [56,138] and orgaometallic reagent formation of organic halides at metal surfaces [22,42-44,94,116]. 

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