Enantioselective Desymmetrization of Glutarimides Catalyzed by Oxazaborolidines Derived from cis-1-Amino-indan-2-ol

Desymmetrization of N-Cbz glutarimides through N-heterocyclic carbene organocatalysis

Over the past decade, the catalysis of N-heterocyclic carbenes has achieved significant advances. In this area, aldehydes, enals, and esters, are commonly employed as starting materials through various catalytic activation modes. However, NHC-activated strategy of amide and its derivatives remains elusive. Described herein is the realization of asymmetric desymmetrization of N-Cbz glutarimides with alcohols through an imide C-N bond cleavage under NHC organocatalysis. A structurally diverse set of enantioenriched 4-amido esters is generated with acceptable yields and high enantioselectivities. This method features mild reaction conditions, excellent substrate scope, and excellent atom economy. DFT calculations have been performed to explore the detailed reaction mechanism and the origin of the enantioselectivity, which indicate that the strength of the C-H···O hydrogen bond and C–H⋯π interactions should be responsible for the stereoselectivity. The current strategy could open a door for efficient construction of (R)-Rolipram with excellent stereoselectivity.

Desymmetrization of achiral building blocks is one of the most efficient ways to access enantiopure compounds of synthetic relevance. Here, the authors desymmetrize glutarimides with alcohols via an imide C–N bond cleavage under NHC organocatalysis.

Divergent Synthesis of γ-Amino Acid and γ-Lactam Derivatives from meso-Glutaric Anhydrides

The first divergent synthesis of both γ-amino acid and γ-lactam derivatives from meso-glutaric anhydrides is described. The organocatalytic desymmetrisation with TMSN₃ relies on controlled generation of a nucleophilic ammonium azide species mediated by a polystyrene-bound base to promote efficient silylazidation. After Curtius rearrangement of the acyl azide intermediate to access the corresponding isocyanate, hydrolysis/alcoholysis provided uniformly high yields of γ-amino acids and their N-protected counterparts. The same intermediates were shown to undergo an unprecedented decarboxylation-cyclisation cascade in situ to provide synthetically useful yields of γ-lactam derivatives without using any further activating agents. Mechanistic insights invoke the intermediacy of an unconventional γ-N-carboxyanhydride (γ-NCA) in the latter process. Among the examples prepared using this transformation are 8 APIs/molecules of considerable medicinal interest.

Highly enantioselective desymmetrization of prochiral cyclic α,α-dicyanoalkenes via the direct vinylogous Michael/cyclization domino reaction

A chiral N,N′-dioxide/Mg(ii) complex efficiently constructs spiroindolinones which include three adjacent atom chiralities and a tertiary carbon center at remote sites in up to 95% yield, with 99% ee and 20 : 1 dr.