Synthesis of α-Diazoketones by The Action of Diazo-N-Octane on 3-Methoxy Cinnamoyl Chloride

Introduction

A number of methods for synthesis of a-diazo ketones by the reaction of higher diazoalkanes with carboxylic acid chlorides or acid anhydrides^1-4. The field of synthesis of new a-diazoketones is too wide^5-7. The study of literature shows that a very little work has been done with higher diazo alkanes^8-10. By using different amount of diazoalkane, it is possible to attack one or both the sites present in it. By doing so, it is possible to compare the reactivity of these sites¹¹. In most cases the acid chloride¹² group is attacked first and the other side afterwards. Thus starting from 3-methoxy cinnamoyl chloride (1 mol) and diazo-n-octane (2 mol and 3 mol) 1-diazo-1-n- heptyl-4-(3-methoxy) phenyl 3-ene-2-one and 4-(3-methoxy) phenyl-3-n-heptyl 1-diazoacetyl-5-n-heptyl pyrazoline were synthesized following the method of Arndt-Eistert.

Above diazoketones were light yellow viscous liquids. The easily removal diazo group present in them, prevented their purification by distillation even under vaccum.

Experimental

Synthesis of 1-diazo-1-n- heptyl-4-(3-methoxy) phenyl 3-ene-2-one 

It was prepared by using 3-methoxy cinnamoyl chloride (2.8 g, 1 mol) on pre-estimated diazo-n-octane (4.32 g, 2 mol) at 0⁰C. The reaction mixture was then kept at 0⁰C overnight. On removal of ether at low temperature the diazoketone was obtained as yellow mobile liquid which contained nitrogen.

 

Synthesis of 4-(3-methoxy) phenyl-3-n-heptyl 1-diazoacetyl-5-n-heptyl pyrazoline

 The diazoketone so obtained was characterised by elemental analyses and its reactions with 2,4-dinitrophenyl hydrazine, benzoic acid, phenol and dry hydrochloric acid. It was prepared by using 3-methoxy cinnamoyl chloride (2.8 g, 1 mol) on pre-estimated diazo-n-octane (6.48 g, 3 mol) at 0⁰C. The reaction mixture was then kept at 0⁰C overnight. On removal of ether at low temperature the diazoketone was obtained as yellow mobile liquid which contained nitrogen.

Results and Discussion

The diazoketone so obtained was characterised by elemental analyses and its reactions with 2,4-dinitrophenyl hydrazine, benzoic acid, phenol and dry hydrochloric acid. The elemental analyses and IR spectral studies were carried out at CDRI Lucknow.

Characterisation of 1-diazo-1-n- heptyl-4-(3-methoxy) phenyl 3-ene-2-one

The diazoketone with an aqueous alcoholic sulphuric acid solution of 2, 4- dinitrophenyl hydrazine gave a 2,4-dinitrophenyl osazone as an orange solid, which after crystallisation from ethanol, melted at 158⁰C (Found C= 55.78%, H = 4.55%, N=17.32%, C₃₀H₃₂O₉N₈, required C= 55.55%, H = 4.93%, N=17.28%) absorbed frequencies IR(KBr) : 3435 (-NH), 1632(C=N), 1620 (-C₆H₅), 1355(C-NO₂), 970(-CH=CH-), 724 Cm^-1 (CH₂ rock in-C₇H₁₅). With dry HCl formed chloroketone afforded 2, 4- dinitrophenyl hydrazone. With benzoic acid gave an ester, afforded 2,4 nitro phenyl hydrazone. (Found C= 63.12%, H = 5.32%, N=9.25%, C₃₁H₃₄O₇N₄, required C= 64.80%, H = 5.92%, N=9.75%) absorbed frequencies IR(KBr) : 3350

(-NH), 1720 (C=O), 1615 (C=N), 1580 (-C₆H₅), 1320(C-NO₂), 965(-CH=CH-), 724 Cm^-1 (CH₂ rock in-C₇H₁₅). With phenol gave an ether, afforded 2,4 nitro phenyl hydrazone.

Scheme 1 Click here to View Scheme

 

Characterisation of 4-(3-methoxy) phenyl-3-n-heptyl 1-diazoacetyl-5-n-heptyl pyrazoline

The diazoketone with an aqueous alcoholic sulphuric acid solution of 2, 4- dinitrophenyl hydrazine gave a 2,4-dinitrophenyl osazone as an orange solid, which after crystallisation from ethanol melted at 132⁰C (Found C= 57.76%, H = 6.20%, N=17.33%, C₃₈H₄₈O₉N₁₀, required C= 57.86%, H = 6.09%, N=17.56%) absorbed frequencies IR(KBr) : 3440 (-NH), 1632(C=N), 1620 (-C₆H₅), 1332(C-NO₂), 725  Cm^-1 (CH₂ rock in-C₇H₁₅). With dry HCl formed chloroketone afforded 2, 4- dinitrophenyl hydrazone. With benzoic acid gave an ester, afforded 2,4 nitro phenyl hydrazone. (Found C= 65.14%, H = 7.25%, N=11.12%, C₃₉H₅₀O₇N₆, required C= 65.54%, H = 7.00%, N=11.76%) absorbed frequencies IR(KBr) : 3350 (-NH), 1720 (C=O), 1625 (C=N), 1590 (-C₆H₅), 1320(C-NO₂), 724 Cm^-1 (CH₂ rock in-C₇H₁₅). With phenol gave an ether, afforded 2,4 nitro phenyl hydrazone.

Scheme 2 Click here to View Scheme

Acknowledgement

The authors are thankful to the principal, Bareilly College, Bareilly and Head, Department of Chemistry for providing necessary facilities and also CD.R.I, Lucknow for various infra red spectra and nitrogen estimation.

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