Unified, efficient, and scalable syntheses of the halichondrin natural products are reported. A newly developed Zr/Ni-mediated one-pot ketone synthesis was used to couple the two halves of the final product at a late stage in the synthesis. With the use of a slight excess of the left halves, the desired ketones were isolated in yields of 80-90 %. The halichondrins were obtained from these ketones in two steps, namely desilylation and [5,5]-spiroketal formation. The new synthetic route was effective for the total synthesis of all members in the homohalichondrin subgroup. The scalability of this process was demonstrated with halichondrin B; 150 mg of halichondrin B (68 % overall yield) were obtained from 200 mg of the right-half precursor.

A highly convergent, stereocontrolled total synthesis of the architecturally complex marine sponge metabolite (−)-enigmazole A has been achieved. Highlights include an unprecedented late-stage large-fragment Petasis–Ferrier union/rearrangement, a multicomponent Type I Anion Relay Chemistry (ARC) tactic, and a dithiane–epoxide union in conjunction with an oxazole-directed stereoselective reduction.

A zirconium/nickel-mediated one-pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp ZrCl was found to dramatically accelerate the coupling and suppress side product formation via an I→SPy displacement at the same time. Unlike Zn/Pd- and Fe/Cu-mediated one-pot ketone syntheses, the new method is effective for nucleophiles bearing OR or equivalent functional groups at the α-position. A mechanism comprising a nickel catalytic cycle, a zirconium catalytic cycle, and Zr→Ni transmetalation is proposed, and Cp ZrCl and/or low-valent Zr species are suggested to play crucial dual roles.

A zirconium/nickel‐mediated one‐pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp2ZrCl2 was found to dramatically accelerate the coupling and suppress side product formation via an I→SPy displacement at the same time. Unlike Zn/Pd‐ and Fe/Cu‐mediated one‐pot ketone syntheses, the new method is effective for nucleophiles bearing OR or equivalent functional groups at the α‐position. A mechanism comprising a nickel catalytic cycle, a zirconium catalytic cycle, and Zr→Ni transmetalation is proposed, and Cp2ZrCl2 and/or low‐valent Zr species are suggested to play crucial dual roles.