Titanocene dichloride

Catalytic metal hydride hydrogen atom transfer (MHAT) reactions have proven to be a powerful method for alkene functionalization. This work reports the discovery of Co‐porphines as highly efficient MHAT catalysts with a loading of only 0.01 mol % for unprecedented chemoselective allene functionalization under photoirradiation. Moreover, the newly developed bimetallic strategy by the combination of photo Co‐MHAT and Ti catalysis enabled the successful carbonyl allylation with a wide range of amino, oxy, thio, aryl, and alkyl‐allenes providing expedient access to valuable β‐functionalized homoallylic alcohols in over 100 examples with exceptional regio‐ and diastereoselectivity. Mechanism studies and DFT calculations supported that selectively transferring hydrogen atoms from cobalt hydride to allenes and generating allyl radicals is the key step in the catalytic cycle.

The daphnezomine A‐type subfamily of Daphniphyllum alkaloids structurally features a unique aza‐adamantane core skeleton and anticipates efficient strategies for completing their syntheses to thoroughly investigate their biological activities. Herein, divergent total syntheses of (−)‐daphnezomines A and B and (+)‐dapholdhamine B have been accomplished in 16–20 steps from a known epoxide via rapid construction of a common core intermediate. The present work features a Ti‐mediated radical cyclization to establish the azabicyclo[3.3.1]nonane ring system, an intramolecular Heck reaction to install the bridgehead all‐carbon quaternary stereocenter, a tandem deprotection/reduction/keto amine‐carbinolamine tautomerization to furnish the aza‐adamantane backbone, and an NIS‐promoted 6‐endo‐trig aminocyclization to assemble the (+)‐dapholdhamine B backbone.