Media-Driven Pd-Catalyzed Reaction Cascades with 1,3-Diynamides Leading Selectively to Either Indoles or Quinolines

Divergent Pd-catalyzed reaction cascades with various 1,3-diynamides yielding either 2-amino-3-alkynylindoles or 2-amino-4-alkenylquinolines were established. Omitting or adding TBAF (tetrabutylammonium fluoride) to the reaction of N,N-(2-iodophenyl)(4-toluenesulfonyl)-1,3-diynamides with secondary or primary amines in the presence of KOH in THF and catalytic amounts of Pd(PPh₃ )₄ completely changed the outcome of the reaction. In the absence of TBAF, 2-amino-3-alkynylindoles were the sole products, while the presence of TBAF switched the product formation to 2-amino-4-alkenylquinolines. Deuterium labeling proceeded selectively at the C3 and C11 positions of the 2-amino-4-alkenylquinoline products and this suggests the unprecedented formation of [4]cumulenimines from 1,3-diynamides as reactive key intermediates.

Crystal structures of (E)-3-(furan-2-yl)-2-phenyl-N-tosylacrylamide and (E)-3-phenyl-2-(m-tolyl)-N-tosylacrylamide

In the title N-tosyl­acryl­amide compounds, (I) and (II), the conformation about the C=C bond is E. In (I), the furan, phenyl and 4-methyl­benzene rings are inclined to the acryl­amide mean plane [–NH—C(= O)—C=C–] by 26.47 (11), 69.01 (8) and 82.49 (9)°, respectively. In (II), the phenyl, and 3-methyl and 4-methyl­benzene rings are inclined to the acryl­amide mean plane by 11.61 (10), 78.44 (10) and 78.24 (10)°, respectively. In the crystals of both compounds, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers with (8) ring motifs.

In the title N-tosyl­acryl­amide compounds, C₂₀H₁₇NO₄S, (I), and C₂₃H₂₁NO₃S, (II), the conformation about the C=C bond is E. The acryl­amide groups, [–NH—C(=O)—C=C–], are almost planar, with the N—C—C=C torsion angle being −170.18 (14)° in (I) and −168.01 (17)° in (II). In (I), the furan, phenyl and 4-methyl­benzene rings are inclined to the acryl­amide mean plane by 26.47 (11), 69.01 (8) and 82.49 (9)°, respectively. In (II), the phenyl, 3-methyl­benzene and 4-methyl­benzene rings are inclined to the acryl­amide mean plane by 11.61 (10), 78.44 (10) and 78.24 (10)°, respectively. There is an intra­molecular C—H⋯π inter­action present in compound (II). In the crystals of both compounds, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R₂²(8) ring motif. In (I), the dimers are reinforced by C—H⋯O hydrogen bonds and linked by C—H⋯π inter­actions, forming chains along [011]. In the crystal of (II), the dimers are linked via C—H⋯O hydrogen bonds, forming chains along [100]. The chains are further linked by C—H⋯π inter­actions, forming layers parallel to (010).

Dissociation of protonated N-(3-phenyl-2H-chromen-2-ylidene)-benzenesulfonamide in the gas phase: cyclization via sulfonyl cation transfer

RATIONALE

In the tandem mass spectrometry of protonated N-(3-phenyl-2H-chromen-2-ylidene)benzenesulfonamides, the precursor ions have been observed to undergo gas-phase dissociation via two competing channels: (a) the predominant channel involves migration of the sulfonyl cation to the phenyl C atom and the subsequent loss of benzenesulfinic acid along with cyclization reaction, and (b) the minor one involves dissociation of the precursor ion to give an ion/neutral complex of [sulfonyl cation/imine], followed by decomposition to afford sulfonyl cation or the INC-mediated electron transfer to give an imine radical cation.

METHODS

The proposed reaction channels have been supported by theoretical calculations and D-labeling experiments.

RESULTS

The gas-phase cyclization reaction originating from the N- to C-sulfonyl cation transfer has been first reported to the best of our knowledge.

CONCLUSIONS

For the substituted sulfonamides, the presence of electron-donating groups (R(2) -) at the C-ring effectively facilitates the reaction channel of cyclization reaction, whereas that of electron-withdrawing groups inhibits this pathway.

Regioselective Synthesis of Highly Substituted Imidazoles via the Sequential Reaction of Allenyl Sulfonamides and Amines

A novel synthesis of imidazoles from electron-withdrawing group-substituted allenyl sulfonamides with amines was developed. The 4- and 5-functionalized imidazoles were constructed regioselectively, which depended on the substituents on the nitrogen atoms.