Stereochemistry of the Reactions of Lithium Di-tert-butylbiphenyl with Alkyl Halides

Article abstract of DOI:10.1021/jo00172a049

The stereochemistry of the reaction of lithium di-tert-butylbiphenyl with cyclopropyl halides, 7-chloronorcarane, 7-bromo-7-methylnorcarane, and anti-3-chloro-exo-tricyclo<3.2.1.0^2,4>octane generated syn/anti lithio reagent ratios of 1:10, 3:1, and 200:1, respectively.Similar treatment of noncyclopropyl secondary halides syn-7-bromonorbornene, anti-7-bromobenzonorbornadiene, exo-2-chloronorbornane, and 4-chloro-tert-butylcyclohexane resulted in lithio reagent ratios of 1:3.8 (syn/anti), 1:1,33 (syn/anti), 10:1 (exo/endo), and 1:14 (cis/trans), respectively.For the cyclopropyl radicals generated in the first group, the lithio reagent ratios describe the related radical equilibrium; the significance of the stereochemistry of the reaction of LiDBB with noncyclopropyl secondary halides is discussed in terms of both precursor radicals and carbanions.