KETENES II KETENES II Thomas T. Tidwell A JOHN WILEY & SONS, INC., PUBLICATION Copyright#2006byJohnWiley&Sons,Inc.Allrightsreserved. PublishedbyJohnWiley&Sons,Inc.,Hoboken,NewJersey. PublishedsimultaneouslyinCanada. Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformor byanymeans,electronic,mechanical,photocopying,recording,scanning,orotherwise,exceptas permittedunderSection107or108ofthe1976UnitedStatesCopyrightAct,withouteithertheprior writtenpermissionofthePublisher,orauthorizationthroughpaymentoftheappropriateper-copyfeeto theCopyrightClearanceCenter,Inc.,222RosewoodDrive,Danvers,MA01923,(978)750-8400, fax(978)750-4470,oronthewebatwww.copyright.com.RequeststothePublisherforpermission shouldbeaddressedtothePermissionsDepartment,JohnWiley&Sons,Inc.,111RiverStreet, Hoboken,NJ07030,(201)748-6011,fax(201)748-6008,oronlineathttp://www.wiley.com/go/ permission. 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LibraryofCongressCataloging-in-PublicationData: Tidwell,ThomasT.,1939- Ketenes/byThomasT.Tidwell.–2nded. p.cm. Includesbibliographicalreferencesandindex. ISBN-13:978-0-471-69282-9 ISBN-10:0-471-69282-4 1. Ketenes. I. Title. QD305.K2T532006 5470.436–dc22 2005013965 PrintedintheUnitedStatesofAmerica 10987654321 Dedicated to Sarah, for her inspiration and support Contents Preface xiii Introduction 1 References 3 1 Structure, Bonding, and Thermochemistry of Ketenes 5 1.1 Theoretical and Computational Studies of Ketenes 5 1.1.1 Molecular and Electronic Structure and Energy 5 References 8 1.1.2 Theoretical and Computational Studies of Ketene Reactions 9 References 12 1.1.3 Substituent Effects on Ketenes 13 References 17 1.2 Molecular Structure Determinations 18 References 21 1.3 Thermochemistry of Ketenes 22 References 25 2 Spectroscopy and Physical Properties of Ketenes 27 2.1 Nuclear Magnetic Resonance Spectroscopy 27 References 33 2.2 Ultraviolet Spectra, Photoelectron Spectra, and Chiroptical Properties 35 References 38 2.3 Infrared Spectra and Raman Spectra 39 References 46 2.4 Dipole Moments 48 References 49 2.5 Mass Spectrometry and Gas Phase Ion Chemistry 49 References 52 3 Preparation of Ketenes 55 3.1 Ketenes from Ketene Dimers 55 References 57 vii viii CONTENTS 3.2 Ketenes from Carboxylic Acids and their Derivatives 57 3.2.1 Ketenes from Carboxylic Acids and Anhydrides 57 3.2.1.1 Ketenes from Carboxylic Acids 57 References 60 3.2.1.2 Ketenes from Acid Anhydrides 61 References 64 3.2.2 Ketenes from Acyl Halides and Activated Acids 65 References 74 3.2.3 Ketenes from Esters 76 3.2.3.1 Ketenes from Ester Enolates 76 3.2.3.2 Ketenes by Ester Pyrolysis 81 References 84 3.2.4 Ketenes by Dehalogenation of a-Halo Carboxylic Acid Derivatives 86 References 89 3.3 Ketenes from Diazo Ketones (Wolff Rearrangements) 90 3.3.1 Thermal Wolff Rearrangement 93 3.3.2 Catalyzed Wolff Rearrangement 97 3.3.3 Photochemical Wolff Rearrangement 104 3.3.4 Other Routes to Ketocarbene Rearrangements 110 References 111 3.4 Ketenes by Photochemical and Thermolytic Methods 114 3.4.1 Ketenes from Cyclobutanones and Cyclobutenones 114 References 129 3.4.2 Ketenes from Photolysis of Cycloalkanones and Enones 132 References 141 3.4.3 Ketenes from Cyclohexadienones and other Cycloalkenones 142 References 151 3.4.4 Ketenes from Dioxinones 153 References 155 3.4.5 Ketenes by Thermolysis of Alkynyl Ethers 156 References 159 3.4.6 Ketenes from other Thermolytic and Photochemical Routes 160 References 169 3.5 Ketenes from Metal Carbene Complexes 171 References 179 3.6 Ketene Formation from Cations and Free Radicals 181 References 182 3.7 Ketenes from Oxidation of Alkynes 183 References 185 3.8 Other Routes to Ketenes 186 References 191 CONTENTS ix 4 Types of Ketenes 193 4.1 Carbon-Substituted Ketenes 193 4.1.1 Alkylketenes 193 References 203 4.1.2 Alkenylketenes 206 References 213 4.1.3 Alkynyl- and Cyanoketenes 214 References 220 4.1.4 Aryl- and Heteroarylketenes 221 References 234 4.1.5 Cyclopropyl-, Cyclopropenyl-, and Oxiranylketenes 237 References 243 4.1.6 Acylketenes 244 References 259 4.1.7 Imidoylketenes 263 References 267 4.1.8 Cumulene-Substituted Ketenes 268 References 273 4.1.9 Ketenes with Charged, Radical, or Carbenic Side Chains 273 References 283 4.1.10 Fulvenones and Cumulenones 284 4.1.10.1 Triafulvenones 285 4.1.10.2 Pentafulvenones 285 References 292 4.1.11 Oxoquinone Methides, Oxoxylylenes, and Related Species 294 References 303 4.2 Nitrogen-Substituted Ketenes 305 References 311 4.3 Oxygen-Substituted Ketenes 313 References 320 4.4 Halogen-Substituted Ketenes 321 4.4.1 Fluoroketenes and Fluoroalkylketenes 321 References 329 4.4.2 Chloro- and Bromoketenes 331 References 340 4.5 Silyl-, Germyl- and Stannylketenes 342 References 358 4.6 Phosphorus-Substituted Ketenes 361 References 369 4.7 Sulfur-Substituted Ketenes 371 References 376 x CONTENTS 4.8 Metal-Substituted Ketenes 377 4.8.1 Ynols and Ynolates 377 References 382 4.8.2 Boron-Substituted Ketenes 384 References 386 4.8.3 Other Metal-Substituted Ketenes and Metal Ketenides 387 References 389 4.8.4 Metal-Complexed Ketenes 389 References 398 4.9 Bisketenes 400 References 422 4.10 Ketenyl Radicals, Anions, and Cations 425 References 427 4.11 Cumulenones 428 References 433 5 Reactions of Ketenes 437 5.1 Oxidation and Reduction of Ketenes 437 References 440 5.2 Photochemical Reactions 441 References 445 5.3 Thermolysis Reactions 446 References 449 5.4 Cycloaddition Reactions of Ketenes 449 References 452 5.4.1 Intermolecular [2þ2] Cycloaddition 453 5.4.1.1 Dimerization of Ketenes 453 References 462 5.4.1.2 Cycloadditions with Alkenes and Dienes 464 References 472 5.4.1.3 Mechanism of Ketene [2þ2] Cycloadditions with Alkenes 474 References 485 5.4.1.4 Cycloaddition of Ketenes with Nucleophilic Alkenes 487 References 492 5.4.1.5 Cycloaddition of Ketenes with Allenes 492 References 494 5.4.1.6 Cycloaddition of Ketenes with Alkynes 495 References 499 5.4.1.7 Cycloaddition of Ketenes with Imines 500 References 510 5.4.2 [3þ2] Cycloadditions of Ketenes 513 References 515 CONTENTS xi 5.4.3 [4þ2] Cycloadditions 516 References 520 5.4.4 Intramolecular Cycloadditions of Ketenes 520 References 525 5.4.5 Cycloaddition of Ketenes with Carbonyl Groups 525 References 531 5.5 Nucleophilic Addition to Ketenes 533 5.5.1 Mechanisms of Hydration of Ketenes 533 References 541 5.5.2 Mechanisms of Amination of Ketenes 543 References 551 5.5.3 Nucleophilic Addition to Ketenes: Preparative Aspects 552 5.5.3.1 Hydride Reduction 552 References 553 5.5.3.2 Reaction of Oxygen Nucleophiles with Ketenes 554 References 559 5.5.3.3 Reaction of Nitrogen Nucleophiles and Electrophiles with Ketenes 560 References 567 5.5.3.4 Carbon and Silicon Nucleophiles 568 References 575 5.5.4 Wittig-Type Reactions 576 References 579 5.6 Electrophilic Addition to Ketones 580 5.6.1 Protonation of Ketenes 580 References 585 5.6.2 Oxygenation of Ketenes 587 References 591 5.7 Radical Reactions of Ketenes 592 References 598 5.8 Polymerization of Ketenes 600 References 602 5.9 Stereoselectivity in Ketene Reactions 603 References 615 5.10 Other Additions to Ketenes 618 5.10.1 Reaction with Diazomethanes 618 5.10.2 Reaction with Sulfur Dioxide 621 5.10.3 Hydrogenation of Ketenes 621 References 621 5.11 Ketene Reactions Using Polymer Supports 622 References 625 Index 627 Preface ItwasacenturyagothatHermannStaudingerintroducedketenestotheworld,and almost50yearsagothatIfirstencounteredthesebeguilingreactiveintermediatesin my first course in organic chemistry, using a textbook written by the inimitable Louis Fieser. Ketenes are remarkable for the variety of ways in which they can be prepared, for their high chemical reactivity, and for the diverse range of useful productsfromtheirreactions.Keteneshavelongbeenrenownfortheiruniquereac- tivityin[2+2]cycloadditionreactionsgivingareadysourceoffourmemberedring compounds, their distinctive characteristic of undergoing facile dimerization, and the high stereoselectivity shown in many of their reactions. The first edition of this book appeared 10 years ago, and even though ketene chemistry seemed at a high point at that time it was predicted ‘‘...in 2005, the opportunitiesforresearchwillbeevengreaterthantheyaretoday.’’Asbettermeth- odology has been devised for ketene preparation and new applications have been found for this family the interest in their chemistry has steadily increased, and the developments over the past decade have exceeded my greatest expectations. This new edition incorporates 1,000 new references, some published in 2005, and to keep the text to a reasonable size just as many have had been dropped. The format of the previous work has proven to be useful and is retained, with 5 principal sections ‘‘Structure, Bonding, and Thermochemistry’’, Spectroscopy and Physical Properties’’, Preparation’’, Types of Ketenes’’, and ‘‘Reactions’’. The text has been completely rewritten with incorporation of new material, and all of the chemical equations and structural formulae have been redrawn in a uni- form style. The extensive lists of known ketenes have not been continued because ofspacerestraints,andbecauseofthepresentcapabilityofsearchingtheseonline. Muchhasbeenlearned,butthereisevenagreateramountstilltobediscovered. Advancesinexperimentaltechniqueshavemademanyclassesofketenesintocon- venientlyobservableintermediates,butotherchallengesremain,particularlyinthe observationofhighlyreactiveketenesbymethodssuchasNMR.Severalclassesof ketenescalculatedtobestablearestillunknownexperimentally,andprovideacon- tinuing challenge. Many surprising new developments may be confidently awaited in the next decade. Thanks are due to the many enterprising chemists around the world who have provided the fascinating results which are reported here. I am particularly grateful toPeterLillya,whograciouslyreadtheentiremanuscript,andtoPatWoodcockfor herinvaluablehelpwiththewritingovermanyyears.Iapologizeforallerrorsand omissions, for which I am solely responsible, and am grateful to those including xiii