Dimethyl 8-acetyl-2-methyl-1,2-dihydroquinoline-2,4-dicarboxylate

In the title compound, C16H17NO5, the six-membered N-containing ring has a half-boat form; the spiro C atom deviates by 0.34 (2) Å from the plane (r.m.s. deviation = 0.051 Å) defined by the N and four aromatic C atoms. Intramolecular N—H⋯O hydrogen bonding generates an S(6) ring motif and the dihedral angle between the mean plane though the S(6) ring and that through the five-atom half-boat plane is 3.39 (2)°. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link molecules into zigzag chains along [001] due to c-glide symmetry, and C—H⋯π interactions extend along [010].

In the title compound, C 16 H 17 NO 5 , the six-membered Ncontaining ring has a half-boat form; the spiro C atom deviates by 0.34 (2) Å from the plane (r.m.s. deviation = 0.051 Å ) defined by the N and four aromatic C atoms. Intramolecular N-HÁ Á ÁO hydrogen bonding generates an S(6) ring motif and the dihedral angle between the mean plane though the S(6) ring and that through the five-atom half-boat plane is 3.39 (2) . In the crystal, weak intermolecular C-HÁ Á ÁO hydrogen bonds link molecules into zigzag chains along [001] due to c-glide symmetry, and C-HÁ Á Á interactions extend along [010].

Comment
Dihydroquinoline moiety is found in a wide variety of natural products and they have attracted a lot of attention from synthetic organic chemists (Kamakshi & Reddy, 2007). 1,2-Dihydroquinolines have received substantial attention due to their potential biological activities arising from their antioxidative properties as well as their usefulness as precursors of some other biologically active compounds (Kim et al., 2001). 1,2-Dihydroquinoline derivatives are known to exhibit a wide spectrum of biological activities such as antimalarial, antibacterial and anti-inflammatory behavior (Yadav et al., 2007).
The crystal packing is stabilized by C10-H10···O3 i intermolecular hydrogen bonds linking the molecules into chains in a zigzag mode along [0 0 1] due to c-glide symmetry, and there are also two C-H···π interactions C14-H14c···Cg1 i and Table 1.).

Experimental
The title compound was synthesized after a method described by Waldmann et al., (2008). 2'-aminoacetophenone (100 mg, 1 eq) was dissolved in acetonitrile (1.5 ml) in a screw-capped test tube and Bi(OTf) 3 (5 mol %, 0.05 eq) was added to the mixture. This mixture were stirred at room temperature for 4 days until the starting material was completely consumed as monitored by TLC. The resultant residue was directly purified by flash chromatography on silica (EtOAc: Cyclohexane 2:98) gave 27% yield as a yellow solid. Recrystallized over pentan and ethyl acetate gave yellow crystalline solid. R f 0.5 (2:1 Cyclohexane/EtOAc); m.p: (374-375 K).

supplementary materials sup-2 Refinement
The H atom of the NH group was located in a difference Fourier map and refined with the constraint N-H = 0.86 (2) Å. All other H atoms were positioned with idealized geometry using a riding model, [C-H = 0.93-0.96Å and U iso = 1.2U eq (C)]. Fig. 1. An ORTEP view of (I), with the atom-numbering scheme and 30% probability displacement ellipsoids. Dashed lines indicate H-bonds.