Push-pull systems: A very useful building blocks for the preparation of biological active heterocycles

INTRODUCTION: Push-pull olefins are compounds containing electrondonating groups (RS) and electron-withdrawing groups (CN) at the opposite ends of a double bond, have attracted considerable attention due to their unusual physicochemical properties, such as high stability, easy E/Zisomerization, and significant charge transfer, that make them suitable for nucleophilic attack. Such compounds are very useful build ing blocks and widely used in organic synthesis. (Scheme 1 ). DISCUSSION: Heterocycles form two thirds of all organic compounds in Nature. There are many heterocycles that are part of our body and many drugs have some type of heterocycles. Our research group has developed nearly 100 patents in recent years, in the field of Synthesis of Heterocycles, starting from push-pull systems. ln reaction scheme 2, it is possible to observe that the primary nucleophilic attack of hydrazine hydrate occurs at the carbon atom of the double bond that is bound to electron donor groups, as can be seen in the resonant structures of scheme 1. The push-pul/ route has already been used to obtain drugs of recognized biological importance, such as 4-hydroxypyrazolo [3,4-d]pyrimidine, or allopurinol1. lmportant antiarthritic drug, which has antitumor and antileukemic activity.The following is a reaction scheme 3 in which some of the heterocycles obtained by us can be appreciated in a few steps of synthesis2-3. ln reviewing the Heterocycles books on the market, we find that there is no book on this subject and none of them contains the experimental procedures for synthesizing the starting materiais of the various types of heterocycles, monocyclics and condensates. For this reason, our group decided to publish a book about the Synthesis of Heterocycles starting from push-pul/ systems this year. This book will also explain the reaction mechanisms and its theoretical basis for the synthesis of the most diverse types of heterocycles and the reaction conditions for the realization of experiments in this field. CONCLUSION: Due to the higher reactivity of the compounds that present push-pull characteristics, the use of this pathway stands out, because the derivative is obtained with fewer reaction steps and higher yields.