(±)-Tetrabenazine was synthesized in six steps from commercially available compounds. The key cyclization substrate was assembled rapidly via Baylis-Hillman and aza-Michael reactions. Annulation of the final ring was achieved through visible light photocatalysis, wherein carbon-carbon bond formation was driven by the oxidation of a tertiary amine. Solvent played a critical role in the photoredox cyclization outcome–whereas methanol led to a mixed ketal, acetonitrile/water (10:1) gave direct cyclization to (±)-tetrabenazine and occurred more rapidly.

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