Acetylenic aryllithiums

C. Cyclization Reaction of Acetylenic Allenyl Lithiums, Vinyllithiums and Aryllithiums... 

The reaction is believed to proceed stepwise to form first an arylvinyliodonium salt (52), which reacts a second time with aryllithium to afford a diarylvinyliodane (53). This iodane undergoes P-elimination to afford eventually the diaryliodonium compound and acetylene, l ... 

A very mild and selective approach to aryl- and hetaryliodonium chlorides 282 is based on the reaction of aryllithium 280 (generated in situ from bromoarenes and butyllithium) with ( )-chlorovinyliodine(in) dichloride (18) (Scheme 2.82) [71,88,89,403,404]. Tlie iodonium transfer reagent 18 is prepared by the reaction of iodine trichloride with acetylene in concentrated hydrochloric acid (Scheme 2.8 in Section 2.1.3.2) [403] caution this compound is highly unstable and should be handled and stored with proper safety precautions [71]. However, the iodonium transfer procedure with reagent 18 is particularly useful for the preparation of bis(hetaryl)iodonium chlorides 283 from the appropriate nitrogen heterocycles 282 (Scheme 2.82) [71]. 

A few examples of thiophilic addition have already been presented above (p. 49). It is a favorite reaction mode of sulfur compounds that occurs with a variety of substrates, for example, between thiobenzophenone (2.0 eq.) and ethynediyidilithium ("dilithio-acetylene" or "dilithium diacetylide"), between 2,5-disubstituted thiophenes and alkyl-or aryllithiums, and between six- or five- membered trithiocarbonates and... 

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