Sparteine-Free, Highly Stereoselective Construction of Complex Allylic Alcohols Using 1,2-Metallate Rearrangements

Stereoselective Synthesis of Allylic Alcohols via Substrate Control on Asymmetric Lithiation

Allylic alcohols are a privileged motif in natural product synthesis and new methods that access them in a stereoselective fashion are highly sought after. Toward this goal, we found that chiral acetonide-protected polyketide fragments performing the Hoppe-Matteson-Aggarwal rearrangement in the absence of sparteine with high yields and diastereoselectivities rendering this protocol a highly valuable alternative to the Nozaki-Hiyama-Takai-Kishi reaction. Various stereodyads and -triads were investigated to determine their substrate induction. The mostly strong inherent stereoinduction was attributed to a combination of steric and electronic effects.

Stereoselective Construction of β-chiral Homoallyl Functionalities by Substrate- and Reagent-Controlled Iterative 1,2-Metallate Rearrangements

Homoallylic alcohols possessing chiral β-centers are considered highly valuable in the synthesis of polyketide-based natural products. Therefore, there is a significant demand for new methods that allow for their stereoselective access. In pursuit of this objective, we have successfully combined our substrate-controlled protocol of Hoppe-Matteson-Aggarwal chemistry with iterative 1,2-metallate rearrangements. Notably, this approach has proven effective in introducing not only primary alcohols but also other functional groups such as alkynes and protected amines.

1,2-Metallate Rearrangement as a Toolbox for the Synthesis of Allylic Alcohols

The development of new methods and protocols for the synthesis of biologically active substances remains one of the most important pillars in organic chemistry, and one of these privileged structural motifs are allylic alcohols. The method of choice to date for the synthesis of these is the Nozaki-Hiyama-Takai-Kishi reaction. We describe here a valuable alternative to the synthesis of allylic alcohols via 1,2-metallate rearrangement. In this work, various vinyl boronic esters with different functional groups have been applied in the Hoppe-Matteson-Aggarwal reaction. In addition, two monoterpenoids were constructed via this convergent synthetic strategy.