HALOGENATION OF ORGANOMETALLICS

See also page 410, Section 2, for additional preparations of vinylic halides via hydrometallation halogenation. 

Colvin, Silicon in Organic Synthesis, Butterworths, London (1981) 

Silicon Reagents for Organic Synthesis, Springer Verlag, New York (1983) 

Larock, Organomercury Compounds in Organic Synthesis, Springer, New York (1985), Chpt 3 

C12/KF-2H20 IC1/KF2H20 LiCl, XeF2 m-ClC6H4C03H / HC1/BF3 OEt2 Br2 

SiX3 reviews — — Syn 761 (1979) OrgRxs 37 57 (1989) See also page 432, Section 2.10. 

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Halogenation of alkenyl organometallic compounds Addition of hydrogen halides to triple bonds Halogenation of alkynes or allenes Addition of alkyl halides to triple bonds Addition of acyl halides to triple bonds... 

Three basic methods have been used for the preparation of organodihaloboranes, RBX2 (1) the direct interaction of hydrocarbons with haloboranes, (2) the reaction of organometallic derivatives with haloboranes, and (3) the halogenation of organoboranes. One of the most convenient laboratory procedures involves the reaction of tetraorganotin derivatives with trihaloboranes, BX3.1-8 This reaction works particularly well for the preparation of alkyldihaloboranes as outlined below. 

The metalation, particularly lithiation, and halogen-to-metal exchange reactions of 1,3,4-oxadiazoles as well as further reactions of organometallic derivatives were reviewed by Grimmett and Iddon (Equation 8) <1995H(41)1525>. 

Organometallic compounds or carbanions undergo a number of reactions in which the carbanion or carbanion-like moiety of the organometallic compound acts as a nucleophilic displacing agent. Examples are the formation of hydrocarbons from alkyl halides, alkyl halides from halogens, and ketones from acid chlorides or esters. The latter two reactions are closely related to the base-catalyzed condensations and are perhaps additions as well as displacement reactions. Related addition reactions are the carbonation of organometallic compounds and the addition to ketones or aldehydes. 

Both of these types of organometallics have the disadvantages of difficulties in preparation and extreme toxicity. Their major advantage is that they provide a controlled reaction, allowing a single halogen of the phosphorus halide to be displaced, leaving the others untouched. 

Syntheses and Structures of Organometallic (Pseudo)Halides RxMX3, x (X = Halogen, N3) 294... 

Coupling of Organometallic Compounds with Aryl Halides, Ethers, and Carboxylic Esters Alkyl-de-halogenation. etc. 

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