Piperidone Ring Research Articles

3,3,5,5-Tetramethyl-r-2,c-6-diphenylpiperidin-4-one

The piperidone ring of the title compound, C21H25NO, adopts a chair conformation with the two phenyl groups equatorially oriented and cis to each other. In the crystal, mol­ecules are linked by weak N—H⋯O hydrogen bonds, forming chains parallel to [100].

1-Methyl-3,3-bis(phenylsulfanyl)piperidin-2-one

The piperidone ring in the title compound, C18H19NOS2, is in a distorted half-chair conformation, distorted towards a twisted boat, with the central methyl­ene C atom of the propyl backbone lying 0.606 (2) Å out of the plane defined by the other five atoms (r.m.s. deviation = 0.1197 Å). One of the S-bound phenyl rings is almost perpendicular to the least-squares plane through the piperidone ring, whereas the other is splayed [dihedral angles = 75.97 (6) and 44.21 (7)°, respectively]. The most prominent feature of the crystal packing is the formation of helical supra­molecular chains along the b axis sustained by C—H⋯O inter­actions. The chains are consolidated into a three-dimensional architecture via C—H⋯π inter­actions whereby one S-bound phenyl ring accepts two C—H⋯π contacts.

2,4-Bis(4-ethoxyphenyl)-7-methyl-3-azabicyclo[3.3.1]nonan-9-one

The mol­ecule of the title compound, C25H31NO3, exists in a twin-chair conformation with an equatorial orientation of the 4-eth­oxy­phenyl groups, as observed for its ortho isomer [Parthiban, Ramkumar, Park & Jeong (2011b ▶), Acta Cryst. E67, o1475–o1476]. The methyl and 4-eth­oxy­phenyl groups are also equatorially oriented on the bicycle, as in the ortho analogue. In particular, although the cyclo­hexa­none ring deviates from an ideal chair, the piperidone ring is closer to an ideal chair, whereas in the ortho isomer both rings are significantly puckered and deviate from ideal chairs. The 4-eth­oxy­phenyl groups on both sides of the secondary amine group are oriented at an angle of 26.11 (3)° with respect to each other, but the 2-eth­oxy­phenyl groups in the ortho isomer are oriented by less than half this [12.41 (4)°]. In contrast to the absence of any significant inter­actions in the crystal packing of the ortho isomer, the title compound features N—H⋯O inter­actions, linking the mol­ecules along the b axis.

Structural characterization of cis-2,6-(E,E)-bis(ferrocenylidene)-N-methyl-4-piperidone and DFT evaluation of alternative polymorphic modifications via ferrocene rotation

The molecular structure of cis-2,6-(E,E)-bis(ferrocenylidene)-N-methyl-4-piperidone (1) has been determined by X-ray crystallography. Compound 1 crystallizes in the monoclinic chiral space group P2(1), a=6.0055(17)Å, b=12.802(4)Å, c=14.465(4)Å, β=95.438(4)°, V=1107.1(5)Å3, Z=2, and Dcalc=1.516Mg/m3; R=0.0335, Rw=0.0682 for 4230 reflections with I>2σ(I). The substituents at the vinyl group of each chalcone moiety exhibit a trans (entgegen) disposition, and the two ferrocene moieties adopt a syn orientation and are located on the side of the piperidone ring opposite of the nitrogen lone electron pair. Molecules of 1 pack in chains along the a axis and exhibit weak intermolecular C-H⋯O hydrogen bonds involving the ferrocene and carbonyl moieties of adjacent molecules. The energy difference between the ferrocene rotational isomers in 1 has been evaluated by DFT, and the lowest energy structure is represented by the solid-state structure. The barriers for the rotational isomerization of the ferrocene groups have been evaluated and are discussed in the context of polymorphic modifications available to 1.

1-Methyl-3,3-bis[(4-methylphenyl)sulfanyl]piperidin-2-one

The piperidone ring in the title compound, C20H23NOS2, has a half-chair distorted to a twisted-boat conformation [Q T = 0.5200 (17) Å]. One of the S-bound benzene rings is almost perpendicular to the least-squares plane through the piperidone ring, whereas the other is not [dihedral angles = 75.28 (5) and 46.41 (5) Å, respectively]. In the crystal, the presence of C—H⋯O and C—H⋯π inter­actions leads to the formation of supra­molecular layers in the ab plane.

Photophysical Properties of Novel Picrate Derivatives – Solvent Effect

H and (13)C NMR spectra were recorded for some novel picrate derivatives derived from 3,3-dimethyl-2,6-diarylpiperidin-4-ones and 3-benzyl-2,6-diarylpiperidin-4-one. The photophysical properties of the picrate derivatives were studied in several solvents, which include a wide range of apolar, polar and protic media. The observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed due to the presence of increased electrostatic interaction between N-protonated piperidone ring and picryl anion ring so that the picryl anion ring lies perpendicular to the plane of the N-protonated piperidone ring i.e., non co-planarity. Such a geometrical change in the excited state leads to an important Stokes shift, reducing the reabsorption and reemission effects in the detected emission in highly concentrated solutions. The higher fluorescence quantum yield of the picrate derivatives are observed in polar media.

5-[(E)-2-Fluorobenzylidene]-8-(2-fluorophenyl)-2-hydroxy-10-methyl-3,10-diazahexacyclo[10.7.1.13,7.02,11.07,11.016,20]henicosa-1(20),12,14,16,18-pentaen-6-one

In the title compound, C33H26F2N2O2, the piperidone ring adopts a half-chair conformation and the pyrrolidine rings adopt half-chair and envelope conformations. The two benzene rings make dihedral angles of 29.58 (5) and 76.33 (5)° with the mean plane of the 1,2-dihydro­acenaphthyl­ene unit. An intra­molecular O—H⋯N hydrogen bond helps to stabilize the mol­ecular structure. In the crystal, inter­molecular C—H⋯F hydrogen bonds link the mol­ecules into [010] chains. Weak C—H⋯π inter­actions are also observed.

11-[(E)-4-Bromobenzylidene]-8-(4-bromophenyl)-14-hydroxy-3,13-diazaheptacyclo[13.7.1.19,13.02,9.02,14.03,7.019,23]tetracosa-1(22),15,17,19(23),20-pentaen-10-one

In the title compound, C35H28Br2N2O2, the piperidone ring adopts a chair conformation and the five-membered ring of the pyrrolidine ring adopts an envelope conformation. The naphthalene ring system makes dihedral angles of 37.12 (8) and 50.62 (9)° with the terminal bromo-substituted benzene rings. The dihedral angle between the two bromo-substituted benzene rings is 72.54 (10)°. In the crystal, adjacent mol­ecules are connected by a pair of inter­molecular C—H⋯O hydrogen bonds, forming an inversion dimer. An intra­molecular O—H⋯N hydrogen bond is also present.

5-[(E)-Benzylidene]-2-hydroxy-10-methyl-8-phenyl-3,10-diazahexacyclo[10.7.1.13,7.02,11.07,11.016,20]henicosa-1(19),12(20),13,15,17-pentaen-6-one ethanol 0.25-solvate 0.6-hydrate

In the title compound, C33H28N2O2·0.25C2H6O·0.6H2O, the piperidone ring adopts a chair conformation and the pyrrolidine ring adopts an envelope conformation. The dihedral angle between the two phenyl rings is 70.83 (16)°. One of the N atoms of the organic mol­ecule is disordered over two positions in a 0.52 (4):0.48 (4) ratio and the two solvent mol­ecules are partially occupied and show high displacement parameters. In the crystal, mol­ecules are connected by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network.

16-[(E)-Benzylidene]-2-hydroxy-12,13-diphenyl-1,11-diazapentacyclo[12.3.1.02,10.03,8.010,14]octadeca-3(8),4,6-triene-9,15-dione

In the title compound, C35H28N2O3, an intra­molecular O—H⋯N hydrogen bonds generates a five-membered ring, producing an S(5) ring motif. The piperidone ring adopts a half-chair conformation and the two pyrrolidine rings adopt an envelope conformation. The dihedral angles formed between adjacent benzene rings are 74.39 (5) and 37.70 (6)°. In the crystal crystal, inter­molecular C—H⋯O hydrogen bonds link mol­ecules into dimers, which are further inter­connected into two-dimensional networks parallel to the ac plane by inter­molecular C—H⋯O hydrogen bonds. The crystal structure is consolidated by weak C—H⋯π inter­actions.

2-Hydroxy-16-[(E)-4-methylbenzylidene]-13-(4-methylphenyl)-12-phenyl-1,11-diazapentacyclo[12.3.1.02,10.03,8.010,14]octadeca-3(8),4,6-triene-9,15-dione

In the title compound, C37H32N2O3, an intra­molecular O—H⋯N hydrogen bond generates a five-membered ring, producing an S(5) motif. The piperidone ring adopts a half-chair conformation. The two fused pyrrolidine rings have similar envelope conformations. The interplanar angles between the benzene rings A/B and C/D are 75.68 (7) and 30.22 (6)°, respectively. In the crystal structure, adjacent mol­ecules are inter­connected into chains propagating along the [010] direction via inter­molecular C—H⋯O hydrogen bonds. Further stabilization is provided by weak C—H⋯π inter­actions.

3,3-Bis[(4-chlorophenyl)sulfanyl]-1-methylpiperidin-2-one

The piperidone ring in the title compound, C18H17Cl2NOS2, has a distorted half-chair conformation. The S-bound benzene rings are approximately perpendicular to and splayed out of the mean plane through the piperidone ring [dihedral angles = 71.86 (13) and 46.94 (11)°]. In the crystal, C—H⋯O inter­actions link the mol­ecules into [010] supra­molecular chains with a helical topology. C—H⋯Cl and C—H⋯π inter­actions are also present.

ChemInform Abstract: Remote Chiral Induction in the Thio-Claisen Rearrangement of Bicyclic Thiolactams.

Abstract A remote steric effect in the bicyclic lactam oxazolidine ring has been shown to affect the stereochemical outcome in the thio-Claisen rearrangement taking place in the piperidone ring.

1-(2-Bromoacetyl)-3-methyl-2,6-diphenylpiperidin-4-one

In the title compound, C20H20BrNO2, the piperidone ring adopts a boat conformation. The phenyl rings are oriented at dihedral angles of 97.8 (2) and 96.0 (1)° with respect to the best plane through the piperidine ring. The dihedral angle between the two phenyl rings is 49.7 (1)°. In the crystal, bifurcated C—H⋯O hydrogen bonds form a R 2 1(7) ring motif, linking the mol­ecules into centrosymmetric dimers.

19-[(E)-4-Chlorobenzylidene]-16-(4-chlorophenyl)-2-hydroxy-1,11-diazahexacyclo[15.3.1.02,10.03,8.010,17.011,15]henicosa-3(8),4,6-triene-9,18-dione

In the title compound, C32H26Cl2N2O3, the piperidone ring adopts a chair conformation and the proline and pyrrolidine rings adopt envelope conformations. The indane ring system is essentially planar with an r.m.s. deviation of 0.011 Å for the non-H atoms. The dihedral angle between the two chloro-substituted benzene rings is 63.69 (10)°. Intra­molecular C—H⋯O and N—H⋯O hydrogen bonds may influence the mol­ecular conformation. In the crystal structure, mol­ecules are connected into layers by weak inter­molecular C—H⋯O hydrogen bonds.

R-2,c-6-Bis(2-methoxyphenyl)-t-3,t-5-dimethylpiperidin-4-one acetic acid solvate

In the title compound, C21H25NO3·C2H4O2, the piperidone ring adopts a chair conformation. The two meth­oxy groups are nearly coplanar with the aromatic rings to which they are attached. The dihedral angle between the two aromatic rings is 60.9 (2)°. There are two short intra­molecular N—H⋯O contacts. The crystal packing is stabilized by inter­molecular O—H⋯N and C—H⋯O inter­actions.

2-Hydroxy-16-[(E)-4-hydroxy-3-methoxybenzylidene]-13-(4-hydroxy-3-methoxyphenyl)-11-methyl-1,11-diazapentacyclo[12.3.1.02,10.03,8.010,14]octadeca-3(8),4,6-triene-9,15-dione

In the title compound, C32H30N2O7, the piperidone ring adopts a chair conformation and the five-membered ring of the dihydro­indenone ring system adopts an envelope conformation. Intra­molecular O—H⋯N and C—H⋯O hydrogen bonds occur. The dihedral angle between the two hydr­oxy-subsituted methoxy­phenyl rings is 71.12 (5)°. In the crystal structure, mol­ecules are connected by inter­molecular O—H⋯O hydrogen bonds, forming layers parallel to (001). These layers are further connected by C—H⋯O hydrogen bonds, forming a three-dimensional network.

Enantioselective Synthesis of (+)-l-733,060 and (+)-CP-99,994: Application of an Ireland-Claisen Rearrangement/Michael Addition Domino Sequence

An efficient asymmetric synthesis of (+)-l-733,060, (-)-(2S,3R)-1 and (+)-CP-99,994, starting from a Baylis-Hillman adduct, is described. The key steps include a novel domino reaction: stereoselective Ireland-Claisen rearrangement, asymmetric Michael addition, and piperidone ring formation through a one-pot reaction hydrogenolysis/lactamization and a stereoselective inversion of a hydroxy group.

(5′′E)-1′′-Benzyl-1′-methyl-5′′-[4-(methylsulfanyl)benzylidene]-4′-[4-(methylsulfanyl)phenyl]dispiro[indoline-3,2′-pyrrolidine-3′,3′′-piperidine]-2,4′′-dione dichloromethane solvate

In the title compound, C38H36N3O2S2·CH2Cl2, the 2-oxindole ring is almost planar (r.m.s. deviation = 0.032 Å), the pyrrolidine ring adopts a twist conformation and the piperidone ring exists as a chair. Three short C—H⋯O intra­molecular contacts occur. In the crystal, mol­ecules are linked by C—H⋯O and C—H⋯N inter­actions. The dichloro­methane solvent mol­ecule is disordered over two orientations in a 0.765 (11):0.235 (11) ratio.

1-Benzyl-3,5-bis(2-thienylmethylene)-4-piperidone

In the title compound, C22H19NOS2, the thio­phene rings form angles of 69.74 (18) and 65.56 (16)° with the benzene ring. The piperidone ring adopts a half-chair conformation due to the presence of the conjugated ketone systems. Both thio­phene rings are disordered over two orientations [occupancies of 0.758 (2)/0.242 (2) and 0.588 (2)/0.412 (2)] at 180° from one another. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds, C—H⋯π and aromatic π–π stacking inter­actions [shortest centroid–centroid separation = 3.865 (3) Å] help to stabilize the packing.