C(O)(=O)CC.C(C1C=CC=CC=1CC)C.C1(=O)OC(=O)CC1.[CH2:23]([C:25]1[CH:26]=[C:27]([CH2:33][CH2:34][CH2:35][C:36]([OH:38])=O)[CH:28]=[CH:29][C:30]=1[CH2:31][CH3:32])[CH3:24]>>[CH2:23]([C:25]1[CH:26]=[C:27]2[C:28](=[CH:29][C:30]=1[CH2:31][CH3:32])[C:36](=[O:38])[CH2:35][CH2:34][CH2:33]2)[CH3:24]3-(3',4'-Diethylenzoyl) propanoic acid (m.p. 93° C, prepared by the acylation of 1,2-diethyl benzene with succinic anhydride) was catalytically reduced to 4-(3',4'-diethylphenyl) butanoic acid (b.p.0.7 143°-147° C). A mixture of this acid (59g; 0.27 mole) and 85% polyphosphoric acid (450g) was warmed to 80° C with stirring for 30 mins. and worked up as in example 8(a) to yield 48.30g (89%) of 6,7-diethyl-1-tetralone, b.p.0.7 118°-122° C. (Found; C, 82.95; H, 9.21; C14H18O requires; C, 83.12;H, 8.97%). Alternatively 4-(3', 4'-diethylphenyl )butanoic acid (23.3g; 0.106 mole) may be cyclised by stirring at 100° C with 80% sulphuric acid (115ml) for 11/2 hrs. After dilution, extraction into ether and distillation 15.53g (74%) of the tetralone was recovered.
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