The transition-metal-catalyzed stereoselective ring-expansion of vinylaziridines and vinyloxiranes

Abstract

Transition-metal-aided stereoselcetive construction of sp3-carbon-rich heterocyclic scaffolds using strained ring systems have received considerable attention in recent years due to their prominent presence in myraids of natural products, bio-active molecules...

Ring expansion/opening reactions of epoxy ene-amides: access to azabicyclononene, tetrahydropyridine and tetrazole scaffolds

“…The reaction of internal epoxide 1l 10 with chloro-diphenylacrylaldehyde ( 2a ) afforded ene-amide 3la . Further treatment of 3la with BF 3 ·OEt 2 produced tetrahydropyridin-3-yl-benzoate 7la in a good yield (Scheme 5, 65%).…”

Regioselective and stereospecific synthesis of functionalized 3,4-dihydro-2H-1,4-thiazines by catalyst-free [3 + 3] annulation of pyridinium 1,4-zwitterionic thiolates and aziridines

“…The desired 3,4-dihydro-2 H -1,4-thiazine products ( R )- 3aa and ( S )- 4au were successfully obtained with no loss of enantiopurity (99% ee) (Scheme 4A). These results suggest that the ring-opening of aziridines 2 is stereospecific via an S N 2 16 or a loose S N 2 17 pathway. For 2-arylaziridines, a loose S N 2 ring-opening reaction took place at the more sterically hindered side of the aziridine ring to furnish intermediates A , which was followed by an N -Michael addition to produce intermediates B , and the desired 3,4-dihydro-2 H -1,4-thiazine products 3 would be generated by a retro-Michael addition/Py extrusion process (Scheme 4B, path a).…”

Organocatalytic Asymmetric [3 + 2]-Annulations of γ-Sulfonamido/γ-Hydroxy-α,β-Unsaturated Ketones with CyclicN-Sulfimines: Synthesis of Chiral Polyheterotricyclic Imidazolidines and Oxazolidines

“…Due to the importance of their molecular skeletons and biological behaviors, extensive efforts have been devoted to the efficient synthesis of these chiral heterocycles. , Several synthetic routes for imidazolidines and oxazolidines have been reported in the past decade. The commonly used methods for chiral imidazolidines and oxazolidines are based on the condensation of aldehydes and ketones with chiral 1,2-diamines and 1,2-amino alcohols, respectively. , Other privileged methods for their asymmetric syntheses are based on the formal [3 + 2]-cycloaddition/annulation of masked-1,3-dipoles with nitrile or carbonyl compounds. , …”