Regiodivergent Intermolecular [3+2] Cycloadditions of Vinyl Aziridines and Allenes: Stereospecific Synthesis of Chiral Pyrrolidines

Abstract

The first rhodium-catalyzed intermolecular [3+2] cycloaddition reaction of vinyl aziridines and allenes for the synthesis of enantioenriched functionalized pyrrolidines was realized. [3+2] cycloaddition with the proximal C=C bond of N-allenamides gave 3-methylene-pyrrolidines in high regio- and diastereoselectivity, whereas, 2-methylene-pyrrolidines were obtained as the major products by the cycloadditions of vinyl aziridines with the distal C=C bond of allenes. Use of readily available starting materials, a broad substrate scope, high selectivity, mild reaction conditions, as well as versatile functionalization of the cycloadducts make this approach very practical and attractive.

Ring strain strategy for the control of regioselectivity. Gold-catalyzed anti-Markovnikov cycloisomerization initiated tandem reactions of alkynes

“…Gold-catalyzed tandem cycloisomerization/hydrogenation of chiral homopropargyl sulfonamides for the synthesis of enantioenriched pyrrolidines Chiral pyrrolidines are highly useful and valuable frameworks that can be found in a large number of biologically active natural products and pharmaceutical agents [53][54][55][56]. In addition, they can also serve as important organocatalysts [57][58][59][60] and ligands in organic synthesis [61][62][63]. Very recently, our group [64] have realized an efficient and general method for the enantioselective synthesis of various pyrrolidines through gold-catalyzed tandem cycloisomerization/hydrogenation of chiral homopropargyl sulphonamides, which represents the first example of a pyrrolidine synthesis from simple homopropargyl sulfonamide.…”

Insights on the Origin of Regiodivergence in the Parallel Kinetic Resolution of rac-Aziridines Using a Chiral Lanthanum–Yttrium Bimetallic Catalyst

“…The utility of new catalytic methods is oftentimes demonstrated by its ability to generate a certain class of building blocks for subsequent synthetic transformations. For instance, enantioselective ring-opening of suitably substituted aziridines can provide a wide range of nitrogen-containing chiral structural motifs such as amino acids. − Stereoselective ring-opening of aziridines, either through desymmetrization of meso -aziridines or through kinetic resolution of rac -aziridines, is noteworthy. − Most of asymmetric synthesis in contemporary practice makes use of transition-metal catalysts. The domain of kinetic resolution is no exception to this trend owing to improved efficiencies offered by transition-metal catalysis. − Although palladium is the most widely used transition metal in catalysis, − use of other transition metals has also witnessed a steady progress. − Interestingly, transition metals are now being employed in conjunction with rare earth metals as well as alkali metals for various catalytic applications. − …”

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

“…For instance, addition of such allenes to Michael acceptors leading to terminal acetylenes has been recently shown [ 8 ]. These allenes give rise to pyrrolidines [ 9 ], pyrroles [ 10 ], chromenes [ 11 ], benzoazepinones [ 12 ], macrolides [ 13 ], and some other carbo- and heterocycles [ 14 – 16 ]. It should be specially emphasized that many compounds containing SO 2 groups are drugs, such as, dapson [ 17 ], oxicams [ 18 ], or amisulpride [ 19 ].…”