“GLYCEROLYSIS OF UREA AS AMMONIA SOURCE FOR MULTI-COMPONENT REACTIONS”

The reaction of glycerol with urea to form glycerol carbonate GC (glycerine carbonate or 4-hydroxymethyl-2-oxo-1,3-dioxolane) is mostly reported in the literature since glycerol carbonate has excellent properties such as low toxicity, biodegradability and a high boiling point which make it a very attractive for a variety chemical of applications.1 One of the most validate reaction mechanism of glycerolysis of urea involves a direct attack by urea to glycerol to form GC and ammonia as by-product obtained by decomposition of urea.2 The aim of this study is the exploitation of the glycerolysis process as an ammonia source to promote a domino reaction on the same plant, consuming ammonia obtained from glycerolysis. The process choosed for the ammonia exploitation was the Hantzsch reaction, one of the main way to obtain dihydropyridines (DHPs), a class of heterocyclic systems with a remarkable pharmacological activity.3 Benzaldehyde and ethyl acetoacetatewere was selected as the most representative reactants for optimizing Hantzsch reaction conditions. A possible reaction mechanism of the domino multi-component reaction is proposed in the Scheme 1.In this work we present the proof-of-principle that our approach, namely dealing with a sealed vessel MW-assisted reaction, and removing ammonia from reaction equilibrium, can give rice to GC and, in turn, DHP in solventless conditions. Actually we’re focusing on the optimization of glycerolisysis of urea overtaking operative difficulties caused by gaseous ammonia. The progress of domino reactions was monitored by GC/MS using the method of standard addition and Hantzsch product was purified by LC chromatography. The yield of the Hantzsch pyridine is referred to isolated compounds and it appears to be quite comparable to the data obtained by method of standard addition. Once confirmed a definitive set of experimental conditions producing the best profile reactions, the yield optimization for urea glycerolisys of and Hantzsch reaction using eco-friendly heterogeneous catalysts, compatible with both reactions, is actually under study.