Ethylenation of secondary and tertiary alkyllithiums. I. Conditions and limits of the reaction

Abstract

The addition of ethylene to isopropyl-and /-butyllithium, previously reported,3 occurs also with secbutyl-and cyclohexyllithium, but not with cyclobutyl-, phenyl-, benzhydryl-, or triphenylmethyllithium. An ether or an amine is a necessary catalyst; both are attacked by alkyllithiums, but not at the low temperatures (below -10°) of these experiments, where the addition of ethylene is still rapid. No other acyclic, unconjugated olefin approaches ethylene in reactivity. The /3-alkylethyllithium, which is formed quantitatively, has been characterized in each case both by carbonation to an acid-ketone mixture and by reaction with benzophenone to a tertiary alcohol whose methyl ether gives rise quantitatively in vapor chromatography to a 1,1 -diphenylalkene. The ethylenation of secondary and tertiary alkyllithium is a reaction of potential synthetic utility.The additions of alkyllithiums to conjugated unsaturated systems such as ,/3-unsaturated ketones, dienes, fulvenes, and styrenes, and also to alkynes, are well-known reactions of synthetic, and in some cases economic, importance. zz-Butyllithium also adds readily to the homoconjugated diene, norbornadiene.1•2 On the other hand, the addition of alkyllithiums to unconjugated carbon-carbon double bonds in hydrocarbon molecules has been observed in comparatively few cases.In 1953, Bartlett, Friedman, and Stiles3 reported that isopropyllithium (1) in ethyl ether at low temperatures adds ethylene at atmospheric pressure, yielding isopentyllithium (2) as the sole reaction product. Similar results were reported for /-butyllithium (3), which formed neohexyllithium (4). In each case the secondary or tertiary alkyllithium added ethylene rapidly under conditons where the primary alkyllithium was inert to ethylene.Primary alkyllithiums are ethylenated only under much more vigorous conditions. In 1950, Ziegler and Gellert4 reported that «-butyllithium in a hydrocarbon solvent adds ethylene at high pressure in an autoclave. Further addition of ethylene to the product yielded a linear polyethylene of low molecular weight.More recently it has been shown that «-butyllithium in the presence of a chelating tertiary amine, such as , , ',N '-tetramethylethylenediamine, will polymerize ethylene at 50 atm pressure and 100°to yield a linear polyethylene5'6 of high molecular weight.Apart from ethylene, the only isolated double bonds reported to undergo addition of organolithiums have been somewhat activated by strain. Mulvaney and Gardlund have reported7 that /-butyllithium adds to the unconjugated double bond of norbornene (5). This retí) G. Wittig and E.

Advances in Carbolithiation

“…Although carbolithiation of the simplest unactivated alkene, ethylene, is known and published in several previous works [27][28][29], intermolecular nucleophilic addition of organolithium reagents across unactivated double bonds in simple terminal and internal alkenes under mild conditions has not been reported in the literature until the past decade. Thus, it was found that dianions derived from aromatic compounds of high reduction potential such as biphenyl or naphthalene, are capable of intermolecular carbolithiation of simple terminal alkenes (Scheme 11.15) [30,31].…”

Activation of C–H bonds of hydrocarbons by the ArH–alkali metal systems in THF (ArH – naphthalene, biphenyl, anthracene, phenanthrene, trans-stilbene, pyrene). Alkylation of naphthalene and toluene with ethene

“…with systems based on polycyclic arenes (biphenyl, naphthalene, phenanthrene) and excess lithium metal (Li: arene = 4:1) in THF at 25°C [12]. Under these conditions, products of the carbolithiation of the above alkenes by the arene dianions are produced after 1-2 h. For other papers concerning addition reactions of organometallic derivatives of alkali metals to alkenes, see [13][14][15][16] and references cited therein.…”

Carbolithiation of o-Amino-(E)-Stilbenes: Diastereoselective Electrophile Substitution with Applications to Quinoline Synthesis

“…Indeed, one of the first uses for alkene carbolithiation was in the anionic polymerization of styrene . The development of carbolithiation chemistry for nonpolymer applications can be traced to the reports of Bartlett et al in which the intermolecular carbolithiation of the simplest unactivated alkene, ethene, was achieved . Subsequently, the carbolithiation of other substituted alkenes such as styrene, β-methylstyrene, and trans -stilbene has been described in detail …”