SCOPE AND LIMITATIONS OF FULVENE SYNTHESES - PREPARATION OF 6-VINYL-SUBSTITUTED AND 6-VINYL-FUNCTIONALIZED FULVENES - FIRST EXAMPLES OF NUCLEOPHILIC-SUBSTITUTION ON A 6-(CHLOROMETHYL)FULVENE

Very few 6-vinylfulvenes have previously been reported in the Literature. In a few cases where Little's procedure (using pyrrolidine as base) has been employed, most enones undergo conjugate attack by the cyclopentadienyl anion followed by either a retroaldol reaction or dihydropentalene formation. In several cases, Diels-Alder reaction of the enone with cyclopentadiene occurs rather than condensation. We have found that in cases where the Little procedure fails to give the desired 6-vinylfulvenes, the Thiele method using NaOH (or NaOMe in some cases) as base gives satisfactory results. In the latter instances, Michael attack is completely suppressed in all but one example. By appropriate choice of base, a variety of fulvenes carrying functional groups on the 6-alkyl position can be prepared. Some of these fulvenes have been shown to undergo further functional group transformations (e.g., nucleophilic substitutions); giving rise to derivatives bearing SR, S(O)R, N-3 or SCN groups.