Synthesis and Chemistry of Agrochemicals PDF
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Synthesis and Chemistry of Agrochemical In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. ACS SYMPOSIUM SERIES 355 Synthesis and Chemistry of Agrochemicals Don R. Baker, EDITOR ICI Americas Inc. Joseph G. Fenyes, EDITOR Buckman Laboratories, Inc. William K. Moberg, EDITOR E. I. du Pont de Nemours & Co. Barrington Cross, EDITOR American Cyanamid Company American Chemical Society, Washington, DC 1987 In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. Library of Congress Cataloging-in-Publication Data Synthesis and chemistry of agrochemicals/Don R. Baker, editor...[et al.]. p. cm.—(ACS symposium series, ISSN 0097-6156; 355) "Developed from a series of symposia sponsored by the Division of Agrochemicals at the 189th-192nd Meetings of the American Chemical Society." Bibliography: p. Includes indexes. ISBN 0-8412-1434-4 1. Pesticides—Synthesis—Congresses Testing—Congresses. I. Baker, Don R., 1933- . II. American Chemical Society. Division of Agrochemicals. III. American Chemical Society. Meeting. IV. Series. TP248.P47S96 1987 668'.65—dc19 87-22304 ISBN 0-8412-1434-4 CIP Copyright © 1987 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, MA 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. ACS Symposium Series M. Joan Comstock, Series Editor 1987 Harvey W. Blanch Vincent D. McGinniss University of California—Berkeley Battelle Columbus Laboratories Alan Elzerman W. H. Norton Clemson University J. T. Baker Chemical Company John W. Finley James C. Randall Nabisco Brands, Inc. Exxon Chemical Company Marye Anne Fox E. Reichmanis The University of Texas—Austin AT&T Bell Laboratories Martin L. Gorbaty C. M. Roland Exxon Research and Engineering Co. U.S. Naval Research Laboratory Roland F. Hirsch W. D. Shults U.S. Department of Energy Oak Ridge National Laboratory G. Wayne Ivie Geoffrey K. Smith USDA, Agricultural Research Service Rohm & Haas Co. Rudolph J. Marcus Douglas B. Walters Consultant, Computers & National Institute of Chemistry Research Environmental Health In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. Foreword The ACS SYMPOSIU medium for publishing symposia quickly in book form. The format of the Series parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that, in order to save time, the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously pub lished papers are not accepted. Both reviews and reports of research are acceptable, because symposia may embrace both types of presentation. In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. Preface ^REVOLUTIONARY CHANGES have linked chemistry with agriculture during this century. Agricultural chemicals, properly chosen and applied, offer great benefit to food and fiber producers and consumers alike. The need for new agrochemicals has not abated. Indeed, the growing demand for safe and effective agricultural chemicals has spurred major research effort for new products. The prime goal of researchers is discovering materials that will economically control plant pathogens insect pests and weeds and at the same time be of minima general. The challenge for scientists who seek to discover and develop new crop protection chemicals has escalated dramatically. It is becoming increasingly more difficult to satisfy the many safety requirements of the various regulatory agencies. The costs associated with development of a new agrochemical are escalating. Until recently, the challenge has been compounded by the lack of regular scientific interchange among those chemists involved in the discovery process. With the ever-increasing world population, the assistance that these new compounds bring to food production is critical. We hope that the work reported here will be useful to those who accept this challenge. We have organized a series of symposia at each national meeting of the American Chemical Society, beginning with the St. Louis meeting in 1984. The aim of these symposia has been to provide a forum for presenting the synthesis and chemistry of new agrochemical agents. In addition, chemists have seized their opportunity to discuss the biological properties of the new materials. These symposia are providing a focus for agricultural chemists. In a similar vein, we hope that this book will provide a view of the current synthetic effort in the agrochemical field. In this volume, a variety of topics has been assembled, ranging from that first symposium to the recent one held in Anaheim in 1986. The chapters in this collection show varied approaches to the discovery process in the agrochemical field, and they represent the current status of these synthetic efforts. The information has been updated to convey the current state of the endeavor. In the past, publication of new synthetic chemistry and the structures of novel agrochemicals has been largely in the patent literature because most of the major advances come from the agrochemical industry. Many xi In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. interesting discoveries have not been made accessible because the compounds lacked commercial potential. The agrochemical synthesis symposia have provided at least a parallel avenue for synthesis chemists to make their discoveries public. Furthermore, these symposia provide a unique forum for this assemblage of pesticide chemistry. Because most of the synthetic effort in the U.S. agrochemical industry is devoted to the development of new herbicides and insecticides, much of the information found in this book is devoted to these two major fields. An effort was also made to give representation to the other important areas of agrochemical synthesis. We particularly appreciate the efforts of those who provided these extraordinary chapters. We express appreciation to the authors for sharing this large amount of useful chemistry and, most importantly, for sharing their practical insight into the workings of biologically active molecules. We thank the companies and organizations that hav hope that by providing a available for agrochemical discovery and by sharing viewpoints of many scientists, this volume can contribute to continuing the successful partner ship of chemistry and agriculture. DON R. BAKER ICI Americas Inc. Richmond, CA 94804 JOSEPH G. FENYES Buckman Laboratories, Inc. Memphis, TN 38108 WILLIAM K. MOBERG Agricultural Products Department E. I. du Pont de Nemours & Co. Wilmington, DE 19898 BARRINGTON CROSS Agricultural Research Division American Cyanamid Company Princeton, NJ 08540 June 9, 1987 xii In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. Chapter 1 Overview of Agrochemical Development Don R. Baker 1, Joseph G. Fenyes 2, William K. Moberg3, and Barrington Cross4 1ICI Americas Inc., 1200 South 47th Street, Richmond, CA 94804 2Buckman Laboratories, 1256 North McLean Boulevard, Memphis, TN 38108 3Agricultural Products Department, E. I. du Pont de Nemours & Co., Experimental Station, Building 402, Wilmington, DE 19898 4Agricultural Research Division American Cyanamid Company P.O Box 400 Since the earliest of recorded time, man has fought with the environment in tilling his fields. At first largely by hand, then with the hoe, and later the plow. First with the aid of animals, later with machinery. Chemicals too, gradually found a place in providing a suitable environment. The Romans used salt to remove unwanted vegetation, and sulfur was used to control a variety of pests. The dawn of the twentieth century saw many inorganic compounds being used as agrochemicals. Then, the 1940's saw the coming of the first generation of synthetic organic agrochemicals including DDT (1), 2,4-D (2), and parathion (3). As technology advances, each step brings certain blessings and often unexpected problems. Such was the case with the first generation of organic agrochemicals. The farmer's yields were greater and costs were lower. But the first generation compounds did not solve all of the problems. DDT was too persistent and had an adverse effect on some species of wildlife (4-5). There was accumulation in the food chain, thin eggshells, and genetic effects in some species. Because of these various health and environ mental concerns, DDT became embroiled in controversy (6- 7). Parathion was too toxic for the average home gardener, indeed, it was too toxic for the average farmer. Even a fine herbicide like 2,4-D had its limitations. It is primarily active on broadleaf plants. This makes it fine for some weeds in small grains and grasses, but useless for broadleaf crops. Here was a need for later generations of herbicides. As 2,4-D controlled the broadleaf weeds, the resistant weeds such as wild oats (Avena fatua), Johnsongrass (Sorghum halepense), and 0097-6156/87/0355-0001$06.00/0 © 1987 American Chemical Society In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. 2 SYNTHESIS AND CHEMISTRY OF AGROCHEMICALS foxtails (Setaria sp.) became problems in the United States. In Europe the problem weeds were the cleavers (Galium sp .) , chickweed (Ste11 aria sp,), blackgrass (Alopecurus myosuroides), and wild oats. Wild oats became such a problem in Europe that control of this single weed was incentive enough to develop herbicides solely for i t s control. Compounds such as diclofop- methyl (ji ) , difenzoquat (90 » and flamprop (10.) were developed to meet this need. The metallic fungicides used in the first half of the twentieth century were largely replaced by the protective fungicides such as captan (11-12) and later the new systemics such as benomyl (13). Gradually the unwanted side effects of these first generation agrochemicals made i t apparent that a successful agrochemical t hav th environ mental, toxicological addition to i t s basi general requirements has several criteria that must be satisfied before a particular compound is commercialized (]A_) . Tens of thousands of compounds must be prepared and tested before one is found that has a suitable combination of properties that will warrant commercial development. Since the cost of generating any new product is stagger ing, only products targeted toward markets which have a high potential for profit are developed. A negative side effect of this process is that chemicals for minor crop markets are often ignored. Therefore, any process that can lessen the number of compounds prepared and tested before a commercial product is found is of major importance. The question is often asked, "How do you discover a new agrochemical?" The random synthesis and screening method gave us the first generation of agrochemicals. As we have seen, however, these compounds were not without their problems. The next successful approach is exemplified by the organophosphate insecticides. Here the dimethyl or diethyl dithiophosphate group was attached to just about any type of available building block. This approach was later extended to include the phosphonate analogs. Through a comparison of the insecticidal and toxicological data, structure-activity theories were developed which provided a means for the synthesis of safer compounds. A similar approach was used in the 2,4-D area. A l l manner of substituted phenoxy and benzoic acids and their derivatives were prepared. As a result, much was learned about the structural relationships for the auxin type action. This analog synthesis procedure has often been called "me too chemistry". The patent literature abounds with examples of such a strategy tried on almost every thing that has shown a modicum of biological activity. Just as 2,4-D i s a mimic of natural auxin, most critical natural products peculiarly associated with plants, insects or microorganisms have been studiea with a wide variety of mimics, and analogs. Now i t is a common In Synthesis and Chemistry of Agrochemicals; Baker, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
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