Water-triggered union of multi-component reactions towards the synthesis of a 4H-chromene hybrid scaffold.

An unprecedented union of multi-component reactions to construct pyrazole- and pyranopyrazole-adorned 4H-chromene from simple reactants in water at ambient temperature is reported. This innovative tactic has integrated two distinct four-component reactions (4CRs) that occur transiently to form four new heterocycles via ten covalent bonds in a single step.

"In Water": Organocatalyzed Diastereoselective Multicomponent Reactions toward 2-Azapyrrolizidine Alkaloid Scaffolds.

Synthesis of the 2-aza analogues of pyrrolizidine and spirooxindole-2-azapyrrolizidine hybrid, a spiro-tetracyclic scaffold possessing multiple contiguous stereocenters, by an exclusive regio-, chemo-, and diastereoselective multicomponent reaction in water is reported. This logical and didactical tactic has integrated the principles of an ideal organic synthesis, privileged substructure-based diversity-oriented synthesis, and biology-oriented synthesis to access hybrid heterocyclic scaffolds.

6-Amino-3,4-dimethyl-4-phenyl-2H,4H-pyrano[2,3-c]pyrazole-5-carbonitrile.

In the title compound, C(15)H(14)N(4)O, the pyrazole ring is aligned at 88.23 (4)° with respect to the aromatic ring and at 3.75 (4)° with respect to the pyran ring. In the crystal, N-H⋯N hydrogen bonds link adjacent mol-ecules into a linear chain motif. C-H⋯N inter-actions are also observed.

Ethyl 2-(6-amino-5-cyano-3,4-dimethyl-2H,4H-pyrano[2,3-c]pyrazol-4-yl)acetate.

In he title compound, C(13)H(16)N(4)O(3), the pyrazole ring is planar (r.m.s. deviation = 0.054 Å). The pyran ring is not planar; the mean plane makes a dihedral angle of 1.9 (1)° with the pyrazole ring. In the crystal structure, inter-molecular N-H⋯N and N-H⋯O inter-actions lead to a linear chain motif.

Ethyl 6-amino-5-cyano-2,4-bis-(4-methyl-phen-yl)-4H-pyran-3-carboxyl-ate.

In the title compound, C(23)H(22)N(2)O(3), the pyran ring adopts a twisted boat conformation. The tolyl rings and carboxyl-ate group are attached to the pyran ring with torsion angles of -77.1 (2), 59.5 (3) and 17.8 (3)°, respectively. The ethyl group is disordered over two orientations with a site-occupancy ratio of 0.508 (5):0.492 (5). In the crystal, mol-ecules are linked by N-H⋯N and N-H⋯O hydrogen bonds, generating a chain running the a axis. Weak C-H⋯O, C-H⋯N and C-H⋯π inter-actions are also observed.