Regioselective synthesis of functionalized ferrocenylphenols based on cyclocondensation reactions of free and masked 1,3-dicarbonyl dianions

Highly functionalized ferrocenyl-substituted phenols were prepared by cyclization of masked or free dianions with 1,3-dielectrophilic 1-η5-ferrocenyl-3,3-bis(methylthio)prop-2-en-1-ones. While the cyclizations of 1,3-bis(silyloxy)-1,3-butadienes (masked dianions) proceed by initial 1,2-addition, the reactions of free 1,3-dicarbonyl dianions proceed by initial 1,4-addition. Therefore, both regioisomeric ferrocenylphenols are available from one and the same electrophile dependent on the type of nucleophile and reaction conditions employed. The reactions reported represent the first examples of the application of formal [3 + 3] cyclizations to the synthesis of organometallic compounds.