Debromination of Aurone Dibromide with Sodium Hydrogen Sulphide

Introduction

Debromination of Vicinal-dihaloakanes and dibromoketones have been studied by earlier workers using the debrominating agents like potassium iodide in acetone¹, stannous chloride in different solvent², sodium hydrogen selenide³, thiourea in ethanol^4,5 and also by some workers using hydrated sodium sulphide under phase transfer condition^6,7 Photochemical and chemical reduction of vicinal dihalides via phase transfer of 4,4¹ bipyridinium radical⁸ for solar energy conversion, use of cobalt octacarbonyl on alumina have been reported for selective dehalogenation of <-bromo sulphoxides⁹. Chromium (II) acetate also brings reductive debromination in vicinal dihaloalkanes¹⁰and chalcone dibromide¹¹. Sodium sulphide with vicinal dibromo derivative of certain oximes is reported to give sulphoxide derivatives.¹² Chalcone with anhydrous sodium sulphide   in acetyl acetone at room temperature is reported to give (Ph-CO -CH₂-CO -Ph) Thiourea with  _2-hydroxy Chalcones gives 1,3 thiamine derivatives in alkaline ethanol on refluxing for 3 hours while in 10 min in DMSO.¹⁴ Sodium polysulphide with chalcone is reported to form 2,4-dibenzoyl -3,5-diphenyl thiolanes¹⁵.

Recently sodium hydrogen sulphide reacts with chalcone dibromide and stibene dibromide in methanol to give chalcone and stibene respectively¹⁶.

It was thought interesting to use sodium hydrogen sulphide for debromination of aurone dibromide in methanol.

Aurone dibromide (0.01 mole) was treated with freshly prepared sodium hydrogen sulphide (0.02 mole) in dry methanol (30 ml.). The reaction mixture was heated for 20 mins, diluted with water and the product was crystallized form ethanol. The product was found to be identical with aurone on the basis of m.p., m.m.p. (mixed melting point) and co-TLC and spectral data of uv-vis, IR and NMR 2,α (4’ methoxy benzyl)coumaran -3- one mp 158 ⁰C.It is white powdery solid  compound having MP-158⁰C. It  does not give any colouration with nautral ferric chloride solution. From the analytical data, the molecular formula was found to be C₁₇ H₁₄ Br₂ 03. The molecular wt is 426

TLC

Rf value was found to be 0.36 for benzene as a solvent on silica gel  G plate with a layer thickness of 0.3 mm. elemental Analysis.

C : found 47.627         C :  Calculated 47.88%

H : found 3.10%         H : Calculated  3.28%

Br   found  38.15%               Br  :   Calculated  37.55%

UV Spectra :UV spectrum was  recorded in methanol and is reproduced on plate no 4 (0) . λ max value are recorded 203.8 nm, 252.2 nm, 363.2 nm and 395.4 nm

corres ponding II – II*           and n – II*  in aurone dibromide

IR spectrum :  IR spectrum was recorded in nujol and reproduced on plate No 4b

Region                        Frequency                               Co-rotation

1750-1725                   1730 (s)                       C = o stretching in 5-membered ring

1300-1200                   1280 (s)                       Ar-o stretching in aromatic ether

1350-1100                   1180 (s)                       C-O stretching

1050-1010                   1010(s)                        -OCH₃ stretching in aromatic ether

750-500                       750 (s)                         C-Br stretching

NMR spectrum

PM R spectrum who recorded in CDCL3  with TMS as an internal standard and in reproduced  on  plate No 4c

The observed chemical shift can be correlated as follows.

1.6 ♪                s           1H                   C-H

2.44 ♪              s           3H                   Ar-CH₃

3.94 ♪              s           3H                   – OCH₃

6.92 – 8.1♪      m         7H                   Ar-H

The white powder having mp=112. It gave blood red colouration with conH₂So₄ from analytical data, the molecular formula was found to br C₁₇ H₁₄ O₃ and molecular mass being 266( by mass spectra.)

Elemental Analysis:

C: found 75.82%                    Calculated 76.13%

H: found 5.324%                    Calculated 5.66%

TLC studies. The RF values  was found to br 0.64 – 0.67 for CCL4 as a solvent on silica gel .G plate with layer thickness of 0.3mm. The UV spectrum it is reproduced on plate No.3a.  It shows λ max value 403.2, 342.8, 254.0 nm corresponding π– π* and n-π* in the compound.

IR Spectrum

IR Spectrum recorded in nujol and is reproduced on flate No.3b. The imp correlation  are as follows.

Region                         Frequency                               Co-rotation

1750-1550                   1700 (s)                       C = o stretching in cydic ketone

1700-1550                   1210 (s)                       C=C Stretching

1310-1210                   1210 (s)                       Ar-o strtching in aromatic rung

1280-1200                   1200(s)                  C-O-Cstretching in 5-membered cyclic ring 1050-1010               1020 (s)                        -OCH₃ stretching in aromatic ether

In addition to after mentioned peaks spectrum also consist peaks coversponding to other common bending, stretching vibration .

PMR spectrum

The PMR spectrum was recorded in CDCL3 in TMS a internal standard and is reproduced on plate No 36.

The observed chemical shift can be correlated as follows.

1.6  ♪               S          1H                   = CH

2.35  ♪             S          3H                   Ar – CH₃

3.8  ♪               S          3H                   Ar – OCH₃

6.87 TO 8♪      m         7H                   Ar – H

6.67  ♪              S         1H                   = CH

Scheme 1 Click here to View scheme

Table 1

Sr No	Aurone dibromide	Aurone	M.P.0C
1	2 ,<Xj-dibromo-2-(4′ methoxy benzylA–5-methyl-coumaran-3-one	2-(4′-methoxy benzylidene) -5-methyl coumaran-3-one	154
2	2, <-dibromoe-2- benzyl 5-methyl-coumaran-3-one	2-benzylidene-5-methyl coumaran-3-one	112
3	2,<-dibromo-2 (4′ methoxy-benzyl) coumaran-3-one	2-(4’methoxy benzylidene)-4-methoxy-coumaran-3-one	140
4	2 ,o-dibromo-2-(4′ methoxy benzyl) 4-tnethoxy coumaran-3-one	2-(4′-methoxy benzylidene-3-nitro-5-methyl coumaran-3-one	180
5	2 ,o<-dibromo-2{4′ methoxy benzyl )-3-nitro-5-methyl coumaran-3-one	2-(4′-methoxy benzylidene) -3-nitro-5-methyl coumaran -3-one	230
6	2,°(-dibromo-2- benzyl -3-nitro-5-methyl coumaran-3-one	2-(41-methoxy benzylidene)-3-bromo-5-methylcoumaran-3-one	226
7	2X-di.bromo-2(4l methoxy-benzyl)-3-bromo-5-methyl coumaran-3-one	2-(4′-methoxy benzylidene) coumaran-3-one	176
8	2,o(-dibromo-2– benzyl —3-bromo-5-methyl coumaran-3-one	2- benzylidene -3-bromo-5-methyl coumaran-3-one	160

References

1. T.S. Wheeley and M.P. Dodwadna-lh, Proc. Ind. Acad, Sci. India, Sect. A            2,1955,            438.
2. P.A.   Soni and  B.J.   Ghiya,   Cury.   Sci 41, 1972,137.
3. T.K. Raja, Indian  J.   Chem, ,   Sect¹³⁷ B, 1976,   812
4. T.C. Sharma and M.M. Bokadia, Indiain J.Chem. Sect. B,14., 1976, 65.
5. R .5. Raghavan,     M.     Govindrajan    and    K.G.    Sanjeev ‘      Babu,   Current             Sci,48, 1979, 1072.
6. D. Landini, L.    Mi lest,    M.L.    Quadri  and   F.  Rolla, J.   Org.   Chem.49,        1984, 152.
7. J. Nakayama, H. Machida and’ M. Hoshino, Tetrahedron Let.24, 1983, 3001.
8.  Z. Goren and I , WMiner, J. Am. Chem. Soc., 165, 1983, 7764. ‘ .
9. H. Alper    and    M,     Copal, J.  Org.  Chem. .48, 1983, 4390.
10. K, Fukunaga and M. YamagucM, Synthesis, 1981, 879.
11. S,W. Sat he  and  B.J . Ghiya,   unpub I shed   work.
12. V.P. Tashchi, A.F. Rukasov, T.I. Orlova, Yu. G. Putsykin and Yu. A. Baskakov,   Khim, Geterotsikl. Soediri,61982, 75. (Chemabst ,S7, , 1982, 109794)
13. R.T.    Lalonde   J, Chem.   Soc.   Chem.   Commun  7,    1982, 401.
14. V.S.   Jamode, Indian J.   Chem.   Sect   B   17,    1979,629.
15. R.T. Lalonde, B.A. Horenstein, K. Schwandler, R.C. Fritz and R.A. Florence,- J. Org. Chem 48, 1983,             4049.
16. A.G. Doshi and B.J. Ghiya J. Indian Chem. Soc.LX III 1986, 404-405.
17. A.G. Doshi, Ph.D. thesis, Amravat i University, Amravati.

---

This work is licensed under a Creative Commons Attribution 4.0 International License.