Butyl halides, butyllithium reactions

In view of three excellent recent reviews on the Parham cyclization, " this section focuses mainly on the more recent literature. While -butyllithium and tert-butyllithium are commonly used to effect halogen-lithium exchange, these reagents do present problems as delineated earlier. Mesityllithium does not pose such problems since the resulting mesityl halides are not susceptible to the side reactions inherent with -butyl and tert-butyl halides. Mesityllithium has been used to prepare the camptothecin precursor 28. This base can also be used with added electrophiles, as for the conversion of 29 to phthalides 30. A more conventional Parham synthesis of phthalides, i.e., 31—>32, has been applied to the synthesis of the aristocularine alkaloids. ... 

Iron-catalyzed Suzuki-Miyaura coupling reactions were also reported by Nakamura and colleagues (entry 27) [67]. Alkyl halides 1 and mixed pinacol aryl(butyl)borates, generated in situ from arylboronates and butyllithium, were used as the reagents and 10 mol% of the iron complexes 16a or 16b as the catalysts. The addition of 20 mol% of MgBr2 was essential for the success of the reaction. Products 3 were isolated in 65-99% yield. The methodology tolerates ester and nitrile functions. The reaction starts probably by initial boron-iron transmetalation to generate a diaryliron(II) complex. 

Reduction of tertiary, allylic, and benzylic halides. NaCNBH, and ZnCI. in a 2 1 molar ratio in ether reduce these halides selectively in —70-90% yield in the presence of primary, secondary, vinyl, and aryl halides. I hc selectivity is comparable to that of lithium 9,9-di-/i-butyl-9-borabicyclol3.3.l nonate, the ate complex obtained by reaction of n-butyllithium with 9-BBN. ... 

Site-specific tritium-labeled arenes. Taylor reports that tritium-labeled aromatics can be obtained by wetting dried ether with tritiated water, adding an aryl halide, cooling to -70°, and then adding n-butyllithium. Trimethylsilyl derivatives of aromatics can be prepared using trimethylchlorosilane in the same way. When the organometaUic intermediate is formed first and then treated with tritiated water, only the unlabeled hydrocarbon is obtained in some cases. Apparently, the cross-metalation reaction is faster than the reaction of -butyl-lithium with either water or trimethylchlorosilane. 

Surprisingly few simple nitroalkanes are commercially available but more complex examples can be prepared readily by alkylation of the anions derived from nitromethane, nitro-ethane, and 2-nitropropane. For example, deprotonation of nitropropane with butyllithium followed by the addition of butyl iodide gives 3-nitroheptane in good yield. This reaction really does have to be done in two steps BuLi is not compatible with alkyl halides ... 

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