2870-04-4

Reaction of [RhCIL2]2 (L = cyclooctene or ethylene) with 2 equiv of the phosphine {1-Et-2,6(CH2P(t)Bu2)2C6H3} (1) in toluene results in a selective metal insertion into the strong Ar-Et bond. This reaction proceeds with no intermediacy of activation of the weaker sp3-sp3 ArCH2-CH3 bond. The identity of complex Rh(Et){2,6-(CH2P(t)Bu2)2C6H3}Cl (3) was confirmed by preparation of the iodide analogue 6 by reaction of the new Rh(η(I)-N2){2,6-(CH2P(t)Bu2)2C6H3} (7) with EtI. It is possible to direct the bond activation process toward the benzylic C-H bonds of the aryl- alkyl group by choice of the Rh(I) precursor, of the substituents on the phosphorus atoms ((t)Bu vs Ph), and of the alkyl moiety (Me vs Et). A Rh(III) complex which is analogous to the product of insertion into the ArCH2-CH3 bond (had it taken place) was prepared and shown not to be an intermediate in the Ar-CH2CH3 bond activation process. Thus, aryl-C activation by Rh(I) is kinetically preferred over activation of the alkyl-C bond in this system. Moreover, cleavage of an Ar-CH2CH3 bond, followed by β-H elimination, may be preferred over sp2-sp3 C-C activation of an Ar-CH3 group.

Composition of the low-boiling fraction of the pyrolysis oil obtained from continuous rectification has been determined by combination of capillary gas-liquid chromatography with other identification methods (catalytic hydrogenation, polymerization).In this way components have been identified which form overall 86.0 per cent (m/m) of the low-boiling fraction.The said pyrolysis oil fraction has been found to contain almost 50 per cent (m/m) of unsaturated components able of polymerization, especially methylindenes, methyl-, ethyl- and dimethylvinylbenzenes, divinylbenzenes and 1,2-dihydronaphthalene.Elution behaviour of all the identified isomeric methylindenes, divinylbenzenes and 1,2-dihydronaphthalene has been evaluated by determination of parameters of the equation Ist.phase(2) = k.Ist.phase(1) + q. The Kovats elution indices of all the identified aromatic hydrocarbons have been determined with the use of a glass capilary column wetted with Carbowax 20M at 80o C.

Methyl and ethyl trifluoromethanesulphonates (' triflates '), prepared by conventional routes involving either trifluoromethanesulphonic acid (' triflic acid ') or its anhydride, contain traces of triflic acid as an impurity, which catalyse their alkylation reactions with aromatic compounds. Pure methyl triflate, obtained from reaction between CH3l and CFS03Ag, does not alkylate p-cymene after several hours at 100 °C. Pure ethyl triflate, prepared by a similar method, is thermally less stable under these conditions, and alkylation takes place only after long induction periods during which some breakdown to triflic acid occurs. With aromatic substrates such as p-cymene or mesitylene the onset of alkylation is followed rapidly by the formation of isomerisation and disproportionation products. Benzyl triflate, prepared from PhCH2Br and CF3SO3Ag, alkylates p-cymene even at room temperature. The strong Lewis acids SbF5 and AlCl3 similarly catalyse alkylation reactions of methyl and ethyl triflates, but BF3, FeCl3, and SnCl4 are much less effective.

An improved continous single step vapor phase process for the preparation of substituted vinylbenzyl chloride from substituted ethyltoluene is disclosed. In this process a substituted ethyltoluene is reacted with a halogen gas in the vapor phase, at elevated temperatures via a continuous feed process. Furthermore, this process achieves halogenation followed by dehydrohalogenation in a single pass through the reactor. There is also obtained a very high total selectivity to vinylbenzyl chloride and its precursors via this continuous process.