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The competitive ortho directing (c.0.d.) influence of a 1-methoxy group and a 4-methyl was studied in the Diels-Alder addition of I-methoxy-l,3-pentadiene (1) to 2,6-dimethylbenzoquinone (2). It was found that the c.0.d. influence of a terminally located niethoxy is stronger than the effect of a terminal methyl group in the diene since only adduct 3 could be isolated. The influence of non-terminal substituents compared to terminal substituents in the diene appears to be insignificant. This was demonstrated by obtaining only adduct 5 from the addition of 3-ethoxy-l,3-pentadiene (4) with 2,6-dimethylbenzoquinone (2). The following order of c.0.d. influence was suggested in the diene relative to a methyl group in the dienophile OCH, > CH3 > H.

A method is described of joining the 2-oxo-butyl group to a ketone. The sequence is illustrated by the synthesis of dihydro-β-ionone (2) from 2,2,6-trimethylcyclohexanone (1).