Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1988 Preparation and utilization of organopalladium intermediates Hanchul Song Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Song, Hanchul, "Preparation and utilization of organopalladium intermediates " (1988). Retrospective Theses and Dissertations. 9729. https://lib.dr.iastate.edu/rtd/9729 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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For the Graduate College Iowa State University Ames, Iowa 1988 ii TABLE OF CONTENTS Page GENERAL INTRODUCTION 1 PART I. TT-ALLYLPALLADIUM FORMATION VIA PALLADIUM-PROMOTED RING-OPENING OF ALKENYLCYCLOALKANES 2 INTRODUCTION 3 RESULTS AND DISCUSSION 7 CONCLUSION 50 EXPERIMENTAL SECTION 51 REFERENCES 81 PART II. PREPARATION OF HETEROCYCLES VIA tc-ALLYLPALLADIUM FORMATION AND INTRAMOLECULAR NUCLEOPHILIC ATTACK ON n-ALLYLPALLADIUM COMPOUNDS 86 INTRODUCTION 87 RESULTS AND DISCUSSION 92 CONCLUSION 107 EXPERIMENTAL SECTION 108 REFERENCES 120 PART III. PREPARATION OF CARBOCYCLES VIA PALLADIUM-PROMOTED INTRAMOLECULAR CYCLIZATION 123 INTRODUCTION 124 RESULTS AND DISCUSSION 129 CONCLUSION 144 EXPERIMENTAL SECTION 145 REFERENCES 163 SUMMARY 165 ACKNOWLEDGEMENTS 166 Preparation and utilization of organopalladium intermediates Hanchul Song Under the supervision of Dr. Richard C. Larock From the Department of Chemistry Iowa State University Ti-Allylpalladium compounds have been prepared from alkenylcycloalkanes bearing 3- and 4-membered rings by reaction with organomercurials and dilithium tetrachloropalladate through à novel palladium-promoted ring- opening process. In the second part of the thesis, re­ ally Ipalladium compounds prepared in situ from various acetoxy-substituted dienes and functionally substituted organomercurials react with base to provide a new route to dihydrobenzofurans and lactones. In the part three of the thesis, cyclic alkenes bearing vinylic halides have been shown to undergo facile, palladium catalyzed cyclization to afford a wide variety of bicyclic cycloalkenes. This methodology allows one to close a 5- or 6-membered ring onto 5-, 6-, and 7-membered ring cyclic alkenes. 1 GENERAL INTRODUCTION Organopalladlum compounds have been known for many years and there exist a large number of procedures available for their preparation. They possess a wide variety of characteristic features which make them suitable intermediates for many synthetic transformations. Aryl- or alkenyl-palladium intermediates usually add across a carbon-carbon double bond. The o-bonded organopalladlum intermediate generated in this manner undergoes syn-p-elimination of Pd-H, Pd-O, or Pd-C (strained 0-0 or 0-0 bond cleavage). The work that is described in this thesis involves this key reaction and is divided into three parts. The first part deals with the preparation of TC- allylpalladium compounds via palladium-promoted ring-opening of alkenylcycloalkanes. The second part involves the synthesis of heterocycles via rc-allylpalladium formation and subsequent intramolecular nucleophilic attack on the resulting n-allylpalladium compounds. The third part deals with the synthesis of carbocycles via palladium-catalyzed intramolecular cyclization. 2 PART I. tc-ALLYLPALLADIUM FORMATION VIA PALLADIUM-PROMOTED RING-OPENING OF ALKENYLCYCLOALKANES 3 INTRODUCTION rc-Allylpalladium compounds were first reported in 1957^. Since that time, a number of procedures have been reported for the synthesis of these compounds^'®. n-Allylpalladium compounds have recently become valuable intermediates in 6 7 organic synthesis ' , particularly for the synthesis of Q naturally occurring organic compounds such as terpenes , pheromones^, macrolide antibiotics*^, and alkaloids**. Two of the more useful methods of preparing these compounds involve the direct allylic hydrogen substitution of alkenes by palladium salts*^"** and the insertion of palladium(O) reagents into the carbon-halogen or carbon-oxygen bond of allylic halides or acetates*®"*®. Besides the methods of synthesis of n-allylpalladium compounds discussed above, there are several important 19 organomercurial routes to these compounds. Heck , and 20 21 Stakem and Heck , and Larock and Mitchell observed that organopalladium compounds prepared by the transmetallation of organomercurials react with conjugated or non-conjugated dienes to afford Ti-allylpalladium compounds (eg. 1). H LlgPdCI^ c RHgCI + H2C=CH(CH2)nCHsaCHa R(GH2)n+i—^) H I H PdCI/2 4 Similarly, vinylmercurials readily react with dilithium tetrachloropalladate (LigRdCl^) and simple acyclic^^'^^ or cyclic alkenes^G to afford good to excellent yields of ir­ ai lylpalladium compounds via palladium hydride rearrangement (eg. 2). H UgPdCI^ I R'OH= CHHgCI + HgC-GHR" R-C<^ • V c— CHZR" (2) H I H PdCI/2 Recently, Larock and Varaprath^* observed that n-allylpalladium compounds can also be prepared by addition of organopalladium compounds to vinylcyclopropanes and vinylcyclobutanes (eg. 3). This reaction apparently involves cHg y /\ Li^PdCU ' RHgCI + H2C=CH-CH ;(CH2)n ^ RCHg——(CH2)nCH3 \/ I I I (3) ^CHZ H I H n.0.1 a cyclopropylcarbinyl to homoallyl ring-opening and subsequent palladium hydride rearrangement. While the palladium chloride ring-opening^®""®® of methylene cyclopropanes®^ has been studied by several groups, those 5 reactions apparently proceed by entirely different mechanisms from the reaction of Larock and Varaprath. More recently, Flschettl and Heck has studied extensively the mechanism of the ring opening of cyclopropylcarblnyl palladium compounds generated either by adding cyclopropylpalladium compounds to alkenes (eq. 4) or adding "phenylpalladlum" to 36 vlnylcyclopropanes . (4) ^ LiPdClg + Ph'^ PdCI/2 The reaction of "cyclopropylpalladium chloride" with styrene gave a n-allylpalladium compound (eq. 4). The reaction of "phenylpalladlum chloride" with vinylcyclopropane gave the same n-allylpalladium compound (eq. 5). These results and the mechanism suggested (eq. 6) are consistent with those of Larock and Varaprath^*. D D PhPdCI (5) D PdCI/g PdCI CIPd Ph (6) HPdCI PdCI h PdCI/2 6 Prior to the initiation of our work on this reaction, little information was available on the generality of this approach to n-allylpalladium compounds and the direction of ring-opening of unsymmetrically substituted cyclopropanes and 24 cyclobutanes. Larock and Varaprath