Limonoids are highly oxygenated C13α-triterpenes and common secondary metabolites. Several hundred congeners have been isolated to date. The first total synthesis of (±)-limonin, the flagship congener of the limonoids, is now reported and features 1) a tandem radical cyclization generating the BCD ring system with the C13α configuration that is essential to the limonoids and a Robinson annulation to construct the limonoid androstane framework, 2) a singlet-oxygen cycloaddition and a Baeyer-Villiger oxidation to synthesize the highly oxidized D ring, and 3) a Suárez reaction to construct the unique AA' ring system.

An indole synthesis via ring expansion of benzocyclobutenone oxime sulfonate was developed. Utility of the indole synthesis was demonstrated by the total synthesis of (+)-CC-1065. The middle and right segments were constructed by a sequential ring expansion of the symmetrical benzo-bis-cyclobutenone. The left segment was also constructed via ring expansion of the methyl-substituted benzocyclobutenone oxime sulfonates. After condensation of these three segments, the dienone cyclopropane structure was formed to complete the total synthesis.

Limonoids are highly oxygenated C13α‐triterpenes and common secondary metabolites. Several hundred congeners have been isolated to date. The first total synthesis of (±)‐limonin, the flagship congener of the limonoids, is now reported and features 1) a tandem radical cyclization generating the BCD ring system with the C13α configuration that is essential to the limonoids and a Robinson annulation to construct the limonoid androstane framework, 2) a singlet‐oxygen cycloaddition and a Baeyer–Villiger oxidation to synthesize the highly oxidized D ring, and 3) a Suárez reaction to construct the unique AA′ ring system.

Reaction of [(η5-C5H4Me)4Fe4(HCCH)(HCC–Br)](PF6) with tBuNH2 forms [(η5-C5H4Me)4Fe4(HCCH)(HCC–NHtBu)](PF6), of which one electron oxidation leads to carbon–carbon bond cleavage to give [(η5-C5H4Me)4Fe4(HCCH)(μ3-CH)(μ3-CNHtBu)](PF6)2, and further treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) affords [(η5-C5H4Me)4Fe4(HCCH)(μ3-CH)(μ3-η1-CNtBu)](PF6). Thus, the HCCBr group is converted to tBuNC and CH groups on the redox-responsive tetrairon core.

A new synthetic route to functionalized 9,10-diarylanthracenes has been developed. 9,10-Epoxyanthracene intermediates were prepared by [4+2] cycloaddition of 1,3-diarylisobenzofuran with a variety of functionalized benzyne intermediates, which were obtained by Mg(TMP)2·2LiCl-mediated benzyne generation. For the cleavage of the resultant 9,10-epoxyanthracene intermediates, we developed mild deoxygenation conditions using a combination of trifluoroacetic acid and Et3SiH. The utility of this sequence was demonstrated by application to the synthesis of 5,7,12,14-tetraphenylpentacene.