Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• decarboxylation reaction (azomethine ylides 7 and ene-sulfonamide 8). Figure 11 shows the structures and relative energies of geometry-optimized isomeric primary products 7 and 8, as well as their tautomeric products 9, 10 and 11 containing the newly formed C–H bonds. These secondary isomers are considerably more

• of water is necessary for this step. 2. The fastest tautomerization in the reaction mixture occurs between 7a and 8 (the ene-sulfonamide). The low barriers (8.4 and 10.6 kcal/mol) should allow the equilibrium to be established rapidly. On the other hand, there is no possibility of proton transfer

• system as in ninhydrin. The resulting intermediates, azomethine ylides or ene-sulfonamide, undergo water-catalyzed tautomerization reactions followed by hydrolysis of the C=N bonds to form amines with a new chiral center at the former C=O group of compound 1. The isolated compound 2 is derived from one

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• -dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles. Keywords: ene-sulfonamide; imine

• the original substrates 1 by swapping the locations of the radical precursor (halide) and the radical acceptor (ene-sulfonamide). The expected products of these reactions, imines like 19, could possibly be used to make spirocyclic oxindole natural products like coerulescine [18], horsfiline [19][20

• needed for the radical precursors was made in high yield as shown in Scheme 3. Vilsmeier–Haack formylation [25] of ene-sulfonamide 20 was followed by sodium chlorite oxidation [26] of the resulting aldehyde (90% yield over two steps). The radical precursors 22–24 were readily made in 54–69% yield by