Synthesis of Carboxylic\nAcids Containing α‑All-Carbon\nQuaternary Centers from Diazo Compounds and Trialkylboranes

The construction of C–C bonds to form all-carbon\nquaternary\ncenters remains a significant challenge in synthetic chemistry. Herein,\nwe report a tandem process involving a 1,2-migration of a tetra-coordinated\nboron intermediate followed by a Claisen rearrangement of the boron\nenolate, achieved through a reaction between allyl diazoacetates and\ntrialkylboranes. The transformation forms two C–C bonds at\nthe carbenic position of diazo substrate in a single-step operation\nunder neutral conditions. Using this method, we successfully realized\nthe gram-scale formal total synthesis of Vincamine, an indole alkaloid\nwith significant pharmacological activity.