(DE4119332-A)      The prodn. of methylidene gp.-contg. alpha,omega-unsatd. oligomers of formula (I) of alpha,omega-diolefins (II) comprises liq.-phase reaction of formula (II) at 150-350 deg.C in the presence of organo-Al cpds. of formula AlX3 or AlX2H (where X = 1-30C aliphatic, alicyclic or aromatic hydrocarbyl). In (I) and (II) R, R' = H, alkyl, aryl, aralkyl or cycloalkyl; x = 1 or 3-25; y = x or 2; n = 0-99; total number of C atoms in the chain is given by: SigmaCk = (x+4)(n+2) - (n+1).    Also claimed are oligomers of formula (I), pref. obtd. from diolefins (II) by the above process.    More specifically pref. (II) are 5C or 7-30C diolefins, opt. substd. with alkyl, aralkyl, aryl or cycloalkyl (except on the terminal double bonds), and opt. also contg. in-chain double bonds; concn. of (III) is 0.1-10 mol.% w.r.t. (II), reaction is carried out in bulk or in inert solvent, and the mol.wt. of (I) is controlled by means of H2 or olefins with only one terminal C=C gp.    USE/ADVANTAGE -   The process enables the prodn. of mainly linear high-mol.wt. hydrocarbons contg. reactive double bonds (I), with more than 70% of the prod. in the oligomer range (n = 3-20). (I) are useful as intermediates for the prodn. of adhesives and lacquers, etc., e.g., by hydrocyanation and hydroformylation followed by oxidn. or hydrogenation.    (US5306856-A)      Mfg alpha-omega-unsatd. oligomers (I) contg. methylidene gp(s). from alpha, omega-diolefins (II) in the presence of a catalytic amt. of organo Al cpds. comprises contacting alpha,omega-diolefins in the liq. phase at 150-350 deg.C with the organo Al cpds. of formula AlX3 or AlX2H and recovering the oligomer; X = aliphatic, alicyclic or aromatic gps. contg. 1-30C. The alpha,omega-diolefins have a chain length of 5-30C and are substd. other than at the terminal double bonds by alkyl, aralkyl, aryl, and cycloalkyl gps.    The concn. of organo Al cpds. is pref. 0.1-10 mol.% based on the amt. of alpha omega-diolefins charged. (I) pref. have general formula (I), R, R1 = H or alkyl, aryl, aralkyl or cycloalkyl; x = 1 or 3-25; y = x or x+2; n = 1-99; and sum of Ck = (x+4)(n+2)-(n+1) = sum of C atoms in the chain. (II) pref. have general formula (II).    USE -   The oligomers are valuable starting materials in the areas of coatings and adhesives, e.g. after hydrocyanisation, and hydroformylation, and further oxidation or hydrogenation.    (EP518021-B1)      A process for preparing methylidene group-containing, alpha,omega-unsaturated oligomers from alpha,omega-diolefins, in the presence of organoaluminium compounds acting as a catalyst, charactrised in that the alpha,omega-diolefins are reacted in the liquid phase at a temperature of 150 to 350degreesC, and the organoaluminium compounds correspond to formula AlX3 or AlX2H, wherein X is an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms.