Homogeneous metalation of alkylbenzenes

Lithiation of toluene by organolithium compounds activated by lithium polyether alkoxides

“…The less basic n-BuLi, yields higher conversion with 100% benzylic positions metallation, whereas sec-BuLi gives some metallation at ring positions. It has also been pointed out by Broaddus [18] that decreasing base strength results in increasing reactivity at benzylic positions. If one accepts the principle that the CH bond will be broken to the largest extent in the transition state involving the weaker base [22], it may be reasonably proposed that electron delocalisation factors will also be largest with the weaker base, i.e.…”

“…None of these procedures is quite satisfactory, due to the involving of difficulty accessible dibenzyl mercury, long reaction time, and erratic occurrence of a mixture of two different, but relatively reactive organometallic compounds. Later on, it has been discovered that tertiary amines activate alkyl lithium compounds [17] in lithiation reactions of alkyl benzene, resulting in behaviour similar to that of alkyl sodium [18]. Using either diazobicyclo octane (DABCO) [5,5] or N , N , N', N' -tetramethylenediamine, Eberhard and Butte [19] found that toluene undergoes quantitative metallation with n-BuLi to give benzyl lithium.…”

Reines α‐metalliertes Benzyllithium durch eine Einkristall‐zu‐Einkristall‐Umwandlung

“…Dies konnte durch Umsetzen der Produkte mit Trockeneis nachgewiesen werden. [7] Interessanterweise beobachteten wir die Bildung von reinem Benzyllithium als Einkristall-Einkristall-Über-gang von farblosen zu gelben Kristallen (Abbildung 1).…”

The reaction of arenetricarbonylchromium complexes with alkyllithium compounds

“…Kinetic control and the lack of transmetalation have previously been observed in the interaction of toluene with the n-butyllithium-tetramethylethylenediammine (TMEDA) adduct (65). In this reaction toluene gives an 89?…”

“…Broaddus observed that the metalation of toluene with the n-butyllithium-TMEDA adduct occurred with less a proton abstraction than the base catalyzed isotopic exchange of toluene (65). This was rationalized in terms of the principle that the C-K bond will be broken to the largest extent in the transition state involving the weakest base.…”