Insights into Regioselective Oxy (−O−) and Imino (−NH−) Group Insertions of 3-Nortricyclanone

Abstract

Lactam 4-azatricyclo[3.2.1.0(2,7)]octan-3-one (16a) was proven to be formed in a previously reported reaction that claimed production of lactam 3-azatricyclo[3.2.1.0(2,7)]octan-4-one (17a). In a related reaction, bicyclo[3.1.0]hex-2-ene-endo-6-carbonitrile (15), lactam (16a), and novel hydroxycarbonitriles 19-21 were selectively formed when 3-nortricyclanone (1) was treated with aqueous hydroxylamine-O-sulfonic acid (HOSA). Since nitrile 15 neither hydrolyzed nor underwent intramolecular Ritter reaction under these conditions, mechanisms involving Beckmann rearrangement of 3 to nitrilium ion 9 (normal) and Beckmann fragmentation of 3 to cation 8 (abnormal) were investigated using semiempirical calculations. When alkaline HOSA was employed, lactams 16a and 17a were formed in a 1:2 ratio, perhaps via oxaziridine 6a. A similar selectivity was observed using an NH(3)/NaOCl reagent solution, which afforded lactone 4-oxatricyclo[3.2.1.0(2,7)]octan-3-one (16b) in addition to both lactams. Consequently, the Baeyer-Villiger oxidation of 1 with NaOCl gave 16b exclusively. Finally, the Schmidt reaction of ketone 1 gave only the lactam 17a, via cyclopropyl migration, and the same fragmentation products obtained from the acidic HOSA reaction. Migration selectivities are rationalized in terms of nucleofugacity, electronic effects, cyclopropyl regulation, and MO theory.

Interruption of Formal Schmidt Rearrangement/Hosomi–Sakurai Reaction of Vinyl Azides with Allyl/Propargylsilanes

“…Recent theoretical studies have shown that from the common transition state with the ID intermediate the fragmentation product (R + and R 1 CN) might also be involved, depending on the R groups, in a way similar to the Beckmann rearrangement of oximes . The fragmentation was preferred, especially when the generated carbocations could be stabilized by their adjacent group . Although scarcely explored, the investigation on the novel adjacent group-mediated ID intermediate might lead to fruitful formally interrupted Schmidt rearrangement, which might be further involved in a novel domino and cascade process for the discovery of novel synthetic methodology.…”