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

Synergistic effects of alkali metals in the alkylation of naphthalene and toluene with ethene in the ArH–alkali metal systems in THF (ArH – naphthalene, phenanthrene)

“…As it has been shown previously [11], the interaction of ethene with the C 10 H 8 -Na system in THF affords 1-ethylnaphthalene (1) (35%) together with small quantities (2%) of its two dihydro derivatives (2 and 3) in a total yield of 37% based on naphthalene. It turned out, however, that if metallic lithium is added to this system the rate of ethene uptake and the efficiency of the naphthalene alkylation are strongly enhanced, reaching a maximum at a Li:Na molar ratio of 2:1 ( Table 1).…”

“…Here too, the process was strongly accelerated when the solid phase of the alkali metal was present in a mixture, whereas the use of DME instead of THF as well as an addition of [15]crown-5 led again to a sharp decrease in the reaction rate, thus indicating on the possible similarity of mechanisms of the H/D exchange and the alkylation. Systems formed on the treatment of a number of other aromatic hydrocarbons (biphenyl, phenanthrene, trans-stilbene, pyrene, anthracene) with alkali metals in THF proved also to be active in the toluene alkylation with ethene at 22°C [11]. In the present article, we report on unusual synergistic effects of alkali metals in the above-mentioned alkylation reactions with ethene in the ArH-alkali metal systems (ArH -naphthalene, phenanthrene) in THF.…”

“…Na met þ ArH g Na þ ¢ Na þ ArH g þ Na at ðaÞ ArH g Na þ þ ArH g Na þ ¢ ArH þ Na þ ArH g þ Na at ðbÞ ArH g Na þ ¢ ArH þ Na at ðcÞ ArH -naphthalene A similar ''cluster" mechanism has been proposed [11] for the reactions of the naphthalene and toluene alkylation with ethene in the ArH-alkali metal systems (ArH -naphthalene, biphenyl, phenanthrene, trans-stilbene, pyrene, anthracene) in THF. According to this mechanism, the formation of the alkylation products occurs here through the step of the ethene insertion into the alkali metal-carbon bonds [M]-R, arising on the surface of clusters as a result of the above-mentioned reversible cleavage of the reactive C-H bonds of a hydrocarbon substrate (RH).…”

“…As part of our ongoing research into CÀH bond activation by non-transition metal compounds [6][7][8][9][10][11], we have previously reported on a high catalytic activity of systems, derived from naphthalene and metallic sodium in THF, in the hydrogen-deuterium exchange of hydrocarbons (naphthalene, benzene, toluene, ethene, methane) at room temperature [8]. A detailed examination of this novel reaction has shown that the rate of the H/D exchange is strongly increased in the presence of the solid phase of the alkali metal in a mixture and drops practically to zero on the replacement of THF by 1,2-dimethoxyethane (DME) as well as on an addition of [15]crown-5 to the system.…”

“…A detailed examination of this novel reaction has shown that the rate of the H/D exchange is strongly increased in the presence of the solid phase of the alkali metal in a mixture and drops practically to zero on the replacement of THF by 1,2-dimethoxyethane (DME) as well as on an addition of [15]crown-5 to the system. Subsequently, it has been established that similar systems based on naphthalene and alkali metals (Li, Na, K) in THF are able to introduce naphthalene and toluene into the alkylation reactions with ethene under ambient conditions yielding linear 1-alkylnaphthalenes (together with small quantities of their dihydro derivatives) and linear and a-branched higher monoalkylbenzenes, respectively [10,11]. Here too, the process was strongly accelerated when the solid phase of the alkali metal was present in a mixture, whereas the use of DME instead of THF as well as an addition of [15]crown-5 led again to a sharp decrease in the reaction rate, thus indicating on the possible similarity of mechanisms of the H/D exchange and the alkylation.…”