REACTION OF 2,6-DISUBSTITUTED PHENOLS WITH VINYLLEAD TRIACETATES AND ALK-1-YNYLLEAD TRIACETATES - SYNTHESIS OF 6-VINYL-CYCLOHEXA-2,4-DIENONES AND 6-ALKYNYL-CYCLOHEXA-2,4-DIENONES AND CRYSTAL-STRUCTURE OF 1,3,5,7-TETRAMETHYL-3,5-BIS(PHENYLETHYNYL)-1,3,4,4A,5,8A-HEXAHYDRO-1,4-ETHENONAPHTHALENE-2,6-DIONE

(E)-Styryllead triacetate 9, generated by reaction of lead tetraacetate with trimethyl[(E)-styryl]stannane 7, has been found to react with 2,4,6-trimethylphenol 1 to give the 6-(E)-styrylcyclohexa-2,4-dienone 11 in high yield. This electrophilic vinylation reaction has been investigated for the vinyllead triacetates 9 and 10 and the 2,6-dimethylphenols 1, 13, 14 and 15. An analogous alkynylation reaction occurred when phenylethynyllead triacetate 24 was treated with 2,4,6-trimethylphenol; however, the product in this case, cyclohexadienone 25, underwent a Diels-Alder dimerisation to give the 1,4-ethenonaphthalene 26. The product 28 from a reaction of the phenylacetylenelead compound 24 and 2,6-dimethylphenol behaved similarly, and here the 1,4-ethenonaphthalene structure 27 for the dimer was determined by single crystal X-ray analysis.