Synthesis of α-Amino Cyclobutanones via Formal 1,3-Hydroxy Migration Triggered by Formation of α-Imino Rhodium Carbene

Abstract

Formal intramolecular 1,3-OH migration of α-imino carbene was achieved producing a unique zwitterion, and the subsequent selective annulation afforded α-amino cyclobutanone. Features such as readily available substrates, mild reaction conditions, a time-saving procedure, excellent functional group compatibility, and valuable transformations of the products qualified this unique protocol as an efficient tool for the synthesis of strained cyclic compounds. Density functional theory calculations were in good agreement with experimental observations, and a plausible mechanism is presented.

Biochemical and structural insights of multifunctional flavin-dependent monooxygenase FlsO1-catalyzed unexpected xanthone formation

“…These cumulative data indicated that the formation of 24 likely involved a 1,3-migration of the C-12a hydroxyl to C-6 after DTC ( 23 )-trapping of the epoxide at C-6a in 22 , causing a spontaneous rearrangement to open the B-ring (Supplementary Fig. 56 ) 41 .…”

Synthesis of Cyclopenta[b]indoles via Rhodium‐Catalyzed Cascade Migration‐Annulation of 1‐Sulfonyl‐1,2,3‐triazoles and Indoles

“…Intramolecular group migration of carbene is an effective strategy to produce multiple‐functionalized zwitterion [10] . Our group developed a migration‐annulation strategy to synthesize valuable (hetero)cyclic compounds [10a–b,11] . For example, in 2020, we reported a 1,3‐acyloxy migration to yield cyclopropane using zwitterion as the key intermediate [11a] .…”

Rhodium-Catalyzed Transannulation of 4,5-Fused 1-Sulfonyl-1,2,3-triazoles with Nitriles. The Selective Formation of 1-Sulfonyl-4,5-fused Imidazoles versus Secondary C–H Bond Migration

“…A competitive intramolecular β-hydrogen shift of the R 1 group is usually occurring in 4-alkyl-1-sulfonyl-1,2,3-triazoles competitive to intermolecular additions, which significantly reduces the yield and selectivity of the products targeted in the latter reactions (Scheme b,c). Other than the intramolecular (1,2-H) migration, various (1, n -H) insertion/annulation strategies were utilized for the preparation of carbocycles and heterocycles from 4-substituted triazole derivatives. − A similar H-migration is observed in the reactions of α-alkyl-α-diazoacetates . To circumvent this, reactions were performed with rhodium­(II) catalysts with bulky carboxylate ligands and at low temperatures. − It was also found that cyclic α-diazocarbonyl compounds are more resistant to the β-hydride shift in comparison with acyclic α-diazoesters .…”