One-pot Synthesis of 2-Hydroxy-1,4-Naphthoquinone (Lawsone).

Aims and Scope: The 2-hydroxy-1,4-naphthoquinone (lawsone) and 2,5-dihydroxy-1, 4-naphthoquninone (5-hydroxylawsone) are synthesized by one step process. The process involves an inexpensive catalyst urea hydrogen peroxide and a base (t-BuOK) in alcohol for the transformation of 1-naphthol or 2,5-dihydroxynaphthalene to lawsone or its derivatives in the presences of oxygen. The process is further directed to produce lawsone or its derivatives, with no extraneous heating to make it energetically efficient. The synthesized compounds are analyzed by FT-IR, 1H and 13C NMR spectral studies. MATERIALS AND METHODS: All the raw materials were purchased from commercial suppliers and used as such without further purification. The infrared spectra were recorded on a Thermo Nicolet-Avatar-330 FT-IR spectrophotometer using KBr (pellets) and noteworthy absorption values (cm-1) are obtained. 1H and 13C NMR spectra are recorded at 293K on BRUKER AMX-400 Spectrometer operating with the frequencies of 300 MHz and 75, 125 MHz respectively using DMSO-d6 as solvent. RESULTS: The 2-hydroxy-1,4-naphthoquinone (lawsone) and 2,5-dihydroxy-1,4-naphthoquninone (5- hydroxylawsone) are synthesised from 1-naphthol and 1,5-dihydorxynaphalene with urea-hydrogen peroxide as the catalyst in basic medium and oxygen as the oxidizing agent. After purification, the formed products are analysed by IR and NMR spectroscopy. The yield is 82% and the purity of the products is > 95%. CONCLUSION: The present study highlights the process for the manufacturing of lawsone and its derivatives which is efficient in terms of energy needed for the activation of products from reactants. The advantages include its cost-effective nature in terms of simple inexpensive catalyst required for the process and high yield. The mild reaction conditions employed and the harmless by product obtained further confirm the usefulness of this synthetic process.

3-[(E)-2-(2-Meth-oxy-phen-yl)vin-yl]-5,5-di-methyl-cyclo-hex-2-enone.

The title compound, C17H20O2, has an E conformation about the bridging C=C bond. The cyclo-hexene ring adopts an envelope conformation with the dimethyl-substituted C atom as the flap. Its mean plane makes a dihedral angle of 7.20 (12)° with the benzene ring. In the crystal, neighbouring mol-ecules are connected via C-H⋯O hydrogen bonds, forming chains running along the a-axis direction.

3-[(E)-2-(4-Chloro-phen-yl)ethen-yl]-5,5-di-methyl-cyclo-hex-2-en-1-one.

In the title compound, C16H17ClO, the cyclo-hexene ring adopts a half-chair conformation and the best plane through the six ring atoms makes a dihedral angle of 6.69 (7)° with the chlorophenyl ring. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol-ecules into centrosymmetric R 2 (2)(20) dimers. The dimers are linked into an infinite chains along the b-axis direction by further C-H⋯O hydrogen bonds.

(E)-3-[4-(Di-fluoro-meth-oxy)-3-hy-droxy-phen-yl]-1-phenyl-prop-2-en-1-one.

In the title compound, C16H12F2O3, the plane of the phenyl ring makes a dihedral angle of 3.22 (8)° with that of the benzene ring. The mol-ecule has an E conformation about the C=C bond. In the crystal, mol-ecules are linked via pairs of O-H⋯O hydrogen bonds, forming inversion dimers which are further consolidated by a pair of C-H⋯O hydrogen bonds. The dimers are linked via C-H⋯O hydrogen bonds, forming columns along the b-axis direction.

3-(4-Chloro-phen-yl)-1-cyclo-propyl-2-(2-fluoro-phen-yl)-5-phenyl-pentane-1,5-dione.

In the title compound, C26H22ClFO2, the cyclo-propane ring is disordered over two orientations, with site-occupancy factors of 0.64 (2) and 0.36 (2). The major occupancy component of the cyclo-propane ring makes dihedral angles of 47.6 (7), 50.4 (7) and 65.4 (7)° with the fluoro-, chloro- and unsubstituted benzene rings, respectively [the corresponding values for the minor occupancy component are 47.6 (12), 51.0 (12) and 60.9 (12)°]. An intra-molecular C-H⋯O hydrogen bond occurs. The F and Cl atoms deviate by 0.0508 (12) and 0.0592 (7) Šfrom the planes of their attached benzene rings. In the crystal, C-H⋯F hydrogen bonds link the mol-ecules into chains along the b-axis direction.

1-Cyclo-propyl-2-(2-fluoro-phen-yl)-5-(4-fluoro-phen-yl)-3-phenyl-pentane-1,5-dione.

In the title compound, C(26)H(22)F(2)O(2), the cyclo-propane ring makes dihedral angles of 47.6 (2), 51.3 (2) and 63.9 (2)° with the 2-fluoro-substituted phenyl ring, the unsubstituted phenyl ring and the 4-fluoro-substituted phenyl ring, respectively. There is a short C-H⋯F contact in the molecule. In the crystal, weak C-H⋯F hydrogen bonds lead to chains of mol-ecules extending along the b-axis direction.

5-(4-Chloro-phen-yl)-1-cyclo-propyl-2-(2-fluoro-phen-yl)-3-phenyl-pentane-1,5-dione.

In the title compound, C(26)H(22)ClFO(2), the cyclo-propane ring makes dihedral angles of 45.7 (2), 49.0 (2) and 65.2 (2)° with the fluoro-substituted phenyl ring, the benzene ring and the chloro-substituted phenyl ring, respectively. The F and Cl atoms deviate by 0.0307 (11) and 0.0652 (6) Å, respectively, from the planes of the phenyl rings to which they are attached. In the crystal, mol-ecules are linked by C-H⋯F hydrogen bonds, forming chains along the b axis.