Effect of solvent on the lithium-bromine exchange of aryl bromides: reactions of n-butyllithium and tert-butyllithium with 1-bromo-4-tert-butylbenzene at 0 degrees C.
The outcome of reactions of 1-bromo-4-tert-butylbenzene (1), a representative aryl bromide, with n-BuLi or t-BuLi at 0 degrees C in a variety of solvent systems has been investigated. The products of reactions of 1 with n-BuLi vary significantly with changes in solvent composition: 1 does not react with n-BuLi in pure heptane; the exchange reaction to give (4-tert-butylphenyl)lithium, which is slow in pure diethyl ether, is virtually quantitative in heptane containing a small quantity of THF; and the reaction of 1 with n-BuLi in THF leads to considerable coupling. Lithium-bromine exchange is the virtually exclusive outcome of reactions of 1 with t-BuLi in every solvent studied except pure heptane: the presence of a small quantity of any of a variety of structurally diverse ethers (Et(2)O, THF, THP, MTBE) in the predominantly hydrocarbon medium affords (4-tert-butylphenyl)lithium, assayed as tert-butylbenzene, in yields exceeding 97%. The only side products observed from reactions of 1 with t-BuLi are small amounts of benzyne-derived hydrocarbons.
Bailey
William F
WF
Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA. william.bailey@uconn.edu
Luderer
Mark R
MR
Jordan
Kevin P
KP
D001555:Benzene Derivatives / Q000737:chemistry*; D001969:Bromobenzenes / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D006536:Heptanes / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013696:Temperature
C000634344:1-bromo-4-tert-butylbenzene; D001555:Benzene Derivatives; D001969:Bromobenzenes; D004987:Ethers; D006536:Heptanes; D009942:Organometallic Compounds; C434823:n-butyllithium; C063841:tert-butylbenzene