Asymmetric hydroalkylation of alkynes and allenes with imidazolidinone derivatives: α-alkenylation of α-amino acids

Abstract

Enantio-, diastereoselective, geometry-selective addition of imidazolidinone derivatives to alkynes and allenes in the presence of LiHMDS in order to obtain quaternary α-alkenyl substituted amino acids in high isolated yields.

Challenges and recent advancements in the synthesis of α,α-disubstituted α-amino acids

“…Beside the arylation of the general amino acids, the same group also disclosed the α-alkenylation of general α-amino acids using similar strategy to extend the applications of this approach 38 . Later, α-alkenylation of general α-amino acids was also reported by the Breit group to furnish the α,α-disubstituted α-alkenyl substituted amino acids 39 . The difference compared to the previous report from the group of Clayden was the achievement of intermolecular α-alkenylation (Fig.…”

“…Another conceptual improvement is to extend the coupling partners towards general alkyl halides 12 and versatile tertiary hydrocarbons which were highly challenging in previous reports 36 .The key to success is the radical-radical coupling of two radical species that are obtained through a one-electron process. α-Functionalization of general α-AAs was also reported recently to realize various α,α-disubstituted α-AAs, especially extending to the arylation and alkenylation of α-amino acids via multi-step pathways [37][38][39] . The key step of the C-C bond formation is the rearrangement reaction to realize the arylation of the amino acid α-center in a diastereoselective manner.…”

Rhodium‐Catalyzed Asymmetric Macrocyclization towards Crown Ethers Using Hydroamination of Bis(allenes)

“…To overcome these limitations, rhodium‐catalyzed allylic addition (RCAA) of pronucleophiles with alkynes and allenes offers an efficient and selective strategy for the atom‐efficient synthesis of branched allylic structures and building blocks (Figure 1A). [6] The mild conditions of this approach allow for broad functional group tolerance, enabling protecting group‐free synthesis, and late‐stage functionalization, which has been practically useful in target‐oriented synthesis of several complex molecules [7,8] . While providing a means for the synthesis of complex molecules, RCAA has also proved to be an efficient strategy for the synthesis of macrocycles.…”

Regio- and diastereoselective transition metal-free hydroalkylation of N-allenyl sulfonamides by push–pull 2-alkynylquinolines

“…Furthermore, alkylation of carbon β of allenes has been reported by using the base (Scheme 1b). 8 To the best of our knowledge, the transition metal- and base-free hydro-alkylation of allenes has never been performed.…”