The Rearrangement of Ketoxime O-Sulfonates to Amino Ketones (The Neber Rearrangement)

Access to a Structurally Complex Compound Collection via Ring Distortion of the Alkaloid Sinomenine

“…Formation of 15 likely occurs through an azirine intermediate as is observed in the Neber rearrangement. 34 Interestingly, 15 resembles the structure of (+)-morphine, and it is known that treatment of naturally occurring (−)-morphine with methanesulfonic acid yields apomorphine. 35 Therefore, similar reaction conditions were applied to 15 , resulting in a ring rearrangement involving aromatization of the C-ring, rearrangement of the D-ring, and addition and migration of a methoxy group to generate expected product 16 (the enantiomer of the apomorphine scaffold) as well as ring-contracted product 17 , which is likely formed through a benzilic acid-type rearrangement.…”

A novel synthetic route for the synthesis of 4,6-diaryl-2-methyl-1,3-benzoxazoles

“…1 H, 13 C and the related 2D NMR spectra were recorded on a Bruker 300 MHz instrument in CDCl 3 using TMS as internal standard. Chemical shifts are given in parts per million (δ-scale) while coupling constants are in Hertz.…”

“…The enones were converted to their oximes 2 by refluxing the alcoholic solution of the enones with an excess of hydroxylamine hydrochloride and sodium acetate. The 13 C NMR spectrum of the crude oxime 2 showed the formation of a major amount of E-isomer and a trace amount of the Zisomer. In the case of 2a, the C-2 olefinic carbon appears at 119.9 ppm for the E-isomer and at 112.4 ppm for the Z-isomer but in the 1 H NMR spectrum, the olefinic hydrogen of the E-isomer appears at 6.67 ppm and that of the Z-isomer gets deshielded and merged with the other aromatic protons.…”

“…The geminal hydrogens H-5'a and H-5'b appeared as a multiplet in between 3.69 ppm and 3.87 ppm. The selected 1 H and 13 C NMR signals of 6 and 7 are given in Tables 2 and 3 respectively.…”

Three‐Membered Heterocycles. Structure and Reactivity

“…Ultimately, it represents a useful protocol for the a-amination of ketones, which has recently been used to advantage in the total synthesis of dragmacidin F [231,232]. While most applications still involve this complete transformation, it became clear early on that the mechanism involved an azirine intermediate that could be isolated under the right conditions [233]. …”