title: Reaction of lithium diethylamide with an alkyl bromide and alkyl benzenesulfonate: origins of alkylation, elimination, and sulfonation.
abstract: A combination of NMR, kinetic, and computational methods are used to examine reactions of lithium diethylamide in tetrahydrofuran (THF) with n-dodecyl bromide and n-octyl benzenesulfonate. The alkyl bromide undergoes competitive S(N)2 substitution and E2 elimination in proportions independent of all concentrations except for a minor medium effect. Rate studies show that both reactions occur via trisolvated-monomer-based transition structures. The alkyl benzenesulfonate undergoes competitive S(N)2 substitution (minor) and N-sulfonation (major) with N-sulfonation promoted at low THF concentrations. The S(N)2 substitution is shown to proceed via a disolvated monomer suggested computationally to involve a cyclic transition structure. The dominant N-sulfonation follows a disolvated-dimer-based transition structure suggested computationally to be a bicyclo[3.1.1] form. The differing THF and lithium diethylamide orders for the two reactions explain the observed concentration-dependent chemoselectivities.
authors.affiliation: Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States.
authors.forename: Lekha
authors.initials: L
authors.lastname: Gupta
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramírez
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D000476:Alkanesulfonates / Q000737:chemistry*; D000478:Alkylation; D001557:Benzenesulfonates / Q000737:chemistry*; D005663:Furans / Q000737:chemistry*; D007700:Kinetics; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D000476:Alkanesulfonates; D001557:Benzenesulfonates; D005663:Furans; D009942:Organometallic Compounds; C018674:tetrahydrofuran; C032365:benzenesulfonic acid; D008094:Lithium