Total Synthesis of Neo‐Tanshinlactones through a Cascade Benzannulation‐Lactonization as the Key Step

Abstract The cascade annulation‐lactonization of phthalides with α‐carboxyfurylacrylates in the presence of lithium hexamethyldisilazide (LiHMDS) provides both convergent and semiconvergent regioselective syntheses of neo‐tanshinlactones in moderate yields. This methodology also offers an avenue for the direct syntheses of hitherto unreported 6‐alkoxycarbonyl‐substituted neo‐tanshinlactones and their heterocyclic analogues. A new synthesis of 4‐alkyl phthalides was developed on the basis of a combination of a Duff reaction and Fürstner cross‐coupling.