We report a ferrocene-mediated electrochemical intermolecular oxidative annulation between malonates and styrenes that avoids the use of excess oxidants such as Mn(OAc)3. The reaction proceeds via presumably the generation of a malonyl radical that adds to the styrene. After further anodic oxidation, the resulting benzylic carbocation is intercepted by one of the esters to deliver the desired γ-lactones.
An efficient Rh(III)-catalyzed annulation between 3-aryl-2H-benzo[b][1,4]oxazines and α-diazo-β-ketoesters was developed, affording a series of polycyclic heteroarenes in moderate to excellent yields with good functional group compatibility. The procedure featured high efficiency, redox neutrality, twofold ortho-C-H activation, and dual [4 + 2] annulation. Moreover, several important intermediates and products have been isolated as powerful evidence for the proposed reaction mechanism.
Tether-directed electrosynthesis of [60]fullerene derivatives fused with 5-membered azacycle and 13-membered carbocycle, that is, bicyclic 1,4,9,12- and 1,2,4,15-adducts, has been achieved unexpectedly for the first time. The novel bicyclic [60]fullerene derivatives are obtained by the electrochemical reduction of [60]fullerene-fused indolines or lactams and subsequent regioselective cyclization with 2,2″-bis(bromomethyl)-1,1′:3′,1″-terphenyl. The product structures have been characterized by spectroscopic data and single-crystal X-ray analysis.
The synthesis of 2- and 6-substituted-3-aminopiperidines from Weinreb amides containing an allylamino fragment is reported. Involving the simultaneous hydrozirconation of the C═C and the C═O bonds, the cyclization was promoted by the BF3-mediated generation of an iminium. Proven to be highly diastereoselective, the sequence can be applied to diversely substituted unsaturated Weinreb amides and valorized through the preparation of bicyclic heterocycles.
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