Bromine with organometallic

In reactions with organometallic agents, the Si-methylated partly C-brominated 1,3,5-trisilacyclohexanes exhibit some similarities — and a number of differences — to their Si-chlorinated C-chlorinated analogues. For example, the 2,2,4,4-tetrabromo-hexamethyl-l,3,5-trisilacyclohexane yields with n-BuLi the dialkylated derivative. 

Deletion of the 17a-hydroxy group similarly leads to an effective topical antiinflammatory agent. Treatment of 16a-methylpregnenolone (244) (obtained by conjugate addition of an organometallic to pregnenolone) sequentially with bromine and acetate ion affords the 21 acetate, 245 (see, for example, the transformation of 196 to 198). In an interesting variation on the method for the introduction of a fluorine atom at 6, the... 

D 1368 23 < 1 mg Pb/L Organometallic lead mineralized by treatment with bromine and steam spectrophotometric determination of dithizone (2) complex. 

Asymmetric synthesis of amino acids.1 These lactones can serve as an optically active form of glycine for synthesis of either D- or L-amino acids. Thus (+ )-1 (or (—)-l) on radical bromination is converted into a single monobromide (2), which can be coupled with nucleophilic organometallic reagents, by either an SN1... 

Isocyanide complexes, such as [AuCl3(PhNC)], may be prepared by reaction of the isocyanide with H[AuC14] or by chlorine oxidation of [AuCl(PhNC)].646 Organometallic derivatives have been prepared in a similar way for example, [Au(C6F5)(PhNC)] with bromine gives [AuBr2(C6Fs)(PhNC)].406... 

Ketones can be a-brominated on solid phase by treatment with synthetic equivalents of bromine, such as pyridinium tribromide (Entry 2, Table 6.1) or phenyltri-methylammonium tribromide (DCM, 20 °C, 3 h [10]). Resin-bound organometallic compounds, such as vinylstannanes [11] or organozinc derivatives [12], react cleanly with iodine to yield the corresponding vinyl or alkyl iodides (see also Section 3.13). Additions of halogens or their synthetic equivalents to C=C double bonds on cross-... 

Figure 5.38 shows an ortho-selective bromination of an aromatic compound that contains a C-bound DMG. Instead of the strong electrophile Br2, the weak electrophile NBS is used. With respect to NBS, this reaction represents an SN2 reaction of the organometallic on the bromine. 

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