Chemoselective Divergent Transformations of N-(Propargyl)indole-2-carbonitriles with Nitrogen Nucleophiles: Alkyne Hydroamination or Domino Cyclizations.

Interactions of N-(propargyl)indole-2-carbonitriles with nitrogen nucleophiles were studied. It was found that lithium hexamethyldisilazane (LiHMDS)-promoted reactions give mixtures of two product types, originating from an initial attack onto carbon-carbon or carbon-nitrogen triple bonds. Performing the reaction at reduced temperature and in the presence of catalytic amounts of LiHMDS delivered alkyne hydroamination products exclusively. On the contrary, the one-pot reaction of N-(propargyl)indole-2-carbonitriles with methanol and LiHMDS on heating, followed by the addition of a nitrogen nucleophile, allowed a selective domino cyclization sequence toward 1-aminopyrazino[1,2-a]indoles. Anilines and nitrogen heterocycles could be employed as N-nucleophiles to obtain products of both types. Moreover, an alternative one-pot route toward a third product type has been developed. When N-(propargyl)indole-2-carbonitrile was first combined with aniline and LiHMDS at reduced temperature, further heating of the in situ generated hydroamination product led to the intramolecular cyclization into 1-imino-2-phenylpyrazino[1,2-a]indoles. Thus, chemodivergent transformations of the same starting material into three compound classes were investigated. The possible reaction routes were studied, and N-(allenyl)indole-2-carbonitrile was identified as the key intermediate. Acyclic and cyclic products exhibit fluorescence emission in the blue to green range.

Hoveyda-Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors.

A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzylamines allowed us to obtain new Hoveyda-Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10-2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).

Crystal structure and Hirshfeld surface analysis of dimethyl (1R*,3aS*,3a1 R*,6aS*,9R*,9aS*)-3a1,5,6,9a-tetra-hydro-1H,4H,9H-1,3a:6a,9-di-epoxy-phenalene-2,3-di-carboxyl-ate.

The title di-epoxy-phenalene derivative, C17H18O6, comprises a fused cyclic system containing four five-membered rings (two di-hydro-furan and two tetra-hydro-furan) and one six-membered ring (cyclo-hexa-ne). The five-membered di-hydro-furan and tetra-hydro-furan rings adopt envelope conformations, and the six-membered cyclo-hexane ring adopts a distorted chair conformation. Two methyl carboxyl-ate groups occupy adjacent positions (2- and 3-) on a tetra-hydro-furan ring. In the crystal, two pairs of C-H⋯O hydrogen bonds link the mol-ecules to form inversion dimers, enclosing two R 2 2(6) ring motifs, that stack along the a-axis direction and are arranged in layers parallel to the bc plane.