· ORGANIC REACTION MECHANISMS 2007 Organic Reaction M echanisms · 2007 An Annual Survey Covering the Literature Dated January to December 2007 Edited by A. C. Knipe © 2011 John Wiley & Sons, Ltd. ISBN: 978-0-470-71238-2 ORGANIC REACTION · MECHANISMS 2007 An annual survey covering the literature dated January to December 2007 Editedby A. C. Knipe University of Ulster Northern Ireland ® AnInterscience Publication A John Wiley and Sons, Ltd., Publication Thiseditionfirstpublished2011 ©2011JohnWiley&Sons,Ltd Registeredoffice JohnWiley&SonsLtd,TheAtrium,SouthernGate,Chichester,WestSussex,PO198SQ, UnitedKingdom Fordetailsofourglobaleditorialoffices,forcustomerservicesandforinformationabouthowtoapply forpermissiontoreusethecopyrightmaterialinthisbookpleaseseeourwebsiteatwww.wiley.com. Therightoftheauthortobeidentifiedastheauthorofthisworkhasbeenassertedinaccordancewiththe Copyright,DesignsandPatentsAct1988. 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LibraryofCongressCatalogCardNumber66-23143 BritishLibraryCataloguinginPublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN978-0-470-71238-2 Typesetin10/12TimesbyLaserwordsPrivateLimited,Chennai,India PrintedandboundinGreatBritainbyTJInternational,Padstow,Cornwall Contributors S.K. ARMSTRONG Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK C.T. BEDFORD Department of Chemistry, University College London, 20GordonStreet,London, WC1H 0AJ,UK M.L. BIRSA Department of Chemistry, Al I Cuza University of Iasi, Bd. Carol I, 11, Iasi 700506, Romania R.G. COOMBES Department of Chemistry, University College London, 20GordonStreet,London, WC1H 0AJ,UK J.M. COXON Department of Chemistry, University of Canterbury, Christchurch, New Zealand M.R. CRAMPTON Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE, UK N. DENNIS 3 Camphorlaurel Court, Stretton, Brisbane, Queensland, 4116, Australia E. GRAS CNRS, LSPCMIB Universite Paul Sabatier, 31062 Toulouse Cedex 9, France A. C. KNIPE Faculty of Life and Health Sciences, University of Ulster, Coleraine, Northern Ireland P. KOˇCOVSKY´ Department of Chemistry, The Joseph Black Building, The University of Glasgow, Glasgow G12 8QQ, UK R.A. McCLELLAND Department of Chemistry, University of Toronto, 80 StGeorgeStreet,Toronto,Ontario,M5S1A1,Canada R.N. MEHROTRA Department of Chemistry, JNV University, Jodhpur, India K.C. WESTAWAY Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario P3E 2C6, Canada v Preface The presentvolume,the forty-third intheseries,surveysresearchonorganic reaction mechanismsdescribedintheavailableliteraturedated2007.Inordertolimitthesizeof thevolume,itisnecessarytoexcludeorrestrictoverlapwithotherpublicationswhich review specialist areas (e.g. photochemical reactions, biosynthesis, electrochemistry, organometallic chemistry, surface chemistry and heterogeneous catalysis). In order to minimize duplication, while ensuring a comprehensive coverage, the editor conducts a survey of all relevant literature and allocates publications to appropriate chapters. While a particularreference maybe allocatedto more thanone chapter,it is assumed that readers will be aware of the alternative chapters to which a borderline topic of interest may have been preferentially assigned. In view of the considerable interest in application of stereoselective reactions to organicsynthesis,wenowprovideindication,inthemargin,ofreactionswhichoccur with significant diastereomeric or enantiomeric excess (de or ee). Please note that following unfortunate slippage in dates of publication of recent volumes it is hoped that the next will be published within nine months. This is a consequenceofstepsalreadytakentoreduceprogressivelythedelaybetweentitleyear and publication date andthereby eventually regainour optimum production schedule. I wish to thank the production staff of John Wiley and Sons and the team of experienced contributors for their efforts to ensure that the review standards of this series are sustained. A.C.K. vii CONTENTS 1. Reactions of Aldehydes and Ketones and their Derivatives by A. C. Knipe....................................................... 1 2. Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and their Derivatives by C. T. Bedford ............................... 47 3. Oxidation and Reduction by R. N. Mehrotra.......................... 69 4. Carbenes and Nitrenes by E. Gras.................................... 133 5. Nucleophilic Aromatic Substitution by M. R. Crampton............... 155 6. Electrophilic Aromatic Substitution by R. G. Coombes................ 167 7. Carbocations by R. A. McClelland.................................... 181 8. Nucleophilic Aliphatic Substitution by K. C. Westaway................ 201 9. Carbanions and Electrophilic Aliphatic Substitution by M. L. Birsa....................................................... 239 10. Elimination Reactions by M. L. Birsa................................. 265 11. Addition Reactions: Polar Addition by P. Kocˇovsky´ .................. 275 12. Addition Reactions: Cycloaddition by N. Dennis...................... 339 13. Molecular Rearrangements: Part 1. Pericyclic Reactions by S. K. Armstrong................................................... 373 14. Molecular Rearrangements: Part 2. Other Reactions by J. M. Coxon...................................................... 397 Author Index........................................................ 457 Subject Index....................................................... 487 ix CHAPTER 1 Reactions of Aldehydes and Ketones and their Derivatives A.C.Knipe Faculty ofLife andHealth Sciences,University of Ulster, Coleraine Formation and Reactions of Acetals and Related Species . . . . . . . . . . . 2 Reactions of Glucosides and Nucleosides . . . . . . . . . . . . . . . . . . . . 6 Reactions of Ketenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Formation and Reactions of Nitrogen Derivatives . . . . . . . . . . . . . . . 7 Imines: Synthesis, Tautomerism, Catalysis . . . . . . . . . . . . . . . . 7 The Mannich and Nitro-MannichReactions . . . . . . . . . . . . . . . . 7 Addition of Organometallics . . . . . . . . . . . . . . . . . . . . . . . . 11 Other Alkylations,Arylations,and Allylationsof Imines . . . . . . . . . 12 Reduction of Imines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Iminium Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Other Reactions of Imines . . . . . . . . . . . . . . . . . . . . . . . . . 14 Oximes, Hydrazones, and Related Species . . . . . . . . . . . . . . . . 16 C–C Bond Formation and Fission:Aldol and Related Reactions. . . . . . . 16 Regio-, Enantio-, and Diastereo-selectiveAldol Reactions . . . . . . . . 16 Mukaiyama and VinylogousAldols . . . . . . . . . . . . . . . . . . . . 21 The Aldol–TishchenkoReaction . . . . . . . . . . . . . . . . . . . . . . 22 Nitrile/Nitro/NitrosoAldols . . . . . . . . . . . . . . . . . . . . . . . . 22 Other Aldol-typeReactions . . . . . . . . . . . . . . . . . . . . . . . . 24 Pinacol-type Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 The Baylis–Hillman Reaction and its Aza and MoritaVariants . . . . . . 25 Allylation and Related Reactions . . . . . . . . . . . . . . . . . . . . . 26 Alkynations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Michael Additions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Other Addition Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 General and Theoretical . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Addition of Organozincs . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Addition of Other Organometallics . . . . . . . . . . . . . . . . . . . . 30 Grignard-type Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . 31 The Wittig Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Hydrocyanation and Cyanosilylation. . . . . . . . . . . . . . . . . . . . 32 Hydrosilylationand Hydrophosphonylation . . . . . . . . . . . . . . . . 33 Miscellaneous Additions . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Enolization and Related Reactions . . . . . . . . . . . . . . . . . . . . . . . 34 Oxidation and Reduction of Carbonyl Compounds . . . . . . . . . . . . . . 34 Regio-, Enantio-, and Diastereo-selectiveReduction Reactions . . . . . . 34 Oxidation Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Other Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Organic Reaction M echanisms · 2007 An Annual Survey Covering the Literature Dated January to December 2007 Edited by A. C. Knipe © 2011 John Wiley & Sons, Ltd. ISBN: 978-0-470-71238-2 1 2 OrganicReactionMechanisms2007 Formation and Reactions of Acetals and Related Species An acid-catalysed 1,5-hydride shift via a tight six-membered ring transition state, of similar overall conformation to the starting structure, has been proposed to account for the deuterium exchange of eight out of twelve methylene hydrogen atoms of 5-hydroxycyclooctanone under acidic (Scheme 1) and basic conditions in D O, as 2 revealed by 1H NMR measurements.1 The reaction has been analysed by quantum chemical calculations and activation barriers have been determined for the catalysed and uncatalysed reactions. D D D D D D O D OD D D OD D D OD D DCl + H H H H D O 2 OD OD +OD D O D D D Scheme1 Conformational,stereoelectronic,andresonanceeffectsontheA1mechanismhave been invoked to explain the effects of ring size and substituents on rates of acid- catalysedhydrolysisoffive-andsix-memberedringcyclicdiol-derivedketoneacetals in mixtures of THF-d and H O with DCl. The results for (1)–(4) reveal resonance 8 2 effects for (2) and (4) and substantial stereoelectronic effects on ring conformation wherebyalignmentoftheequatorialorpseudo-equatoriallonepairwiththeσ∗ orbital of the breaking C−O bond can explain why a five-membered ring ethanediol-derived acetalstronglyresemblesasix-memberedring2,2-dimethylpropanediol-derivedacetal and why the corresponding cyclic propanediol-derived acetals hydrolyse faster than both of these.2 O O +H+ O O+H r.d.s. +O OH −H+ R1 R2 R1 R2 R1 R2 R1 = Me (1) = CH CH R2 = MeCHCl 2 2 (2) = CH2CH2 R2 = CH2=CH (3) = CH CR CH a; R = H, b; R = Me R2 = MeCHCl 2 2 2 (4) = CH2CR2CH2 a; R = H, b; R = Me R2 = CH2=CH Scheme2 Chemoselective, quantitative transacetalization of aldehyde O,O- and O,S-cyclic acetals into the corresponding S,S-acetals in the presence of ketones or their acetals 1ReactionsofAldehydesandKetonesandtheirDerivatives 3 and oxathioacetals has been reported.3 The reactions were promoted using RSH or HSCH CH SH in DMF at room temperature, with cyanuric acid as the catalyst. 2 2 Ketene diethyl acetal (5) has been found to undergo Michael–Dieckmann-type reactionswith2-acylaminoacrylates(6a)and(6b)togiveformal2+2-and2+2+2- cycloaddition products, respectively (Scheme 3).4 The results have been interpreted theoretically in terms of a polar stepwise mechanism. OEt OEt R = Me OEt OEt MeO C formal 2 NHCOMe (5) 2 + 2 + O R = CF CO Me 3 2 formal 2 + 2 + 2 OEt NHCOR MeO C 2 NHCOCF 3 (6) a; R = M b; R = CF 3 Scheme3 A study of the Lewis acid-mediated reactions of cyclopropanone acetals (7) with alkylazides has established that the product(s) obtained are markedly dependent on ring substituents R(cid:3), R(cid:3)(cid:3), giving (8) and (9) [from azide addition to the carbonyl, followedbyringexpansionorrearrangement,respectively],whereR(cid:3),R(cid:3)(cid:3) =H,H,(10) [fromC(2)–C(3)bondcleavageofthecorrespondingcyclopropanone,givingoxyallyl cations that are captured by azides], where R(cid:3),R(cid:3)(cid:3) =Me,Me, (11) [also the result of EtO OTMS O R O N R–N 3 R′ BF3•OEt2 EtO NHR R″ (7) (8) (9) O N F F Me N B + O N R Me NHR R′ (10) (11) 4 OrganicReactionMechanisms2007 C(2)–C(3) bond rupture, azide capture, and loss of nitrogen] where R(cid:3),R(cid:3)(cid:3) =Ar,H, and (8) and (11), where R(cid:3),R(cid:3)(cid:3) =n-C H ,H. Reasons for the contrasting behaviour 6 13 have been discussed.5 The Brønsted acid-catalysed formal insertion of an isocyanide into a C−O bond of a diverse array of acyclic and cyclic acetals (Scheme 4) can be achieved in the presenceofnitro,cyano,halogen,ester,andalkoxygroups,butthecourseofthereac- tion is highly dependent on the structure of the isocyanide; an electron-deficient aryl isocyanide is required to obtain the monoinsertion product, otherwise double inser- tion of two aryl isocyanide molecules may occur.6 The reaction of t-octyl isocyanide also induces a double incorporation, but the subsequent acid-mediated fragmentation leadstothe2-alkoxyimidoyl cyanide.The monoinsertionproducts,α-alkoxyimidates, can readily be hydrolysed to α-alkoxy esters, realizing the formyl carbonylation of an acetal. NAr R OMe 10 mol% R + Ar N C: TfOH OMe Toluene OMe 30 °C, h OMe Ar = 2,6-ClCH 2 6 3 Scheme4 A detailed kinetic study of the pH dependence of the multistate reaction of 6- (cid:3) hydroxy-4-(dimethylamino)flavylium hexafluorophosphate in aqueous solutions has revealed relatively slow hydrative formation of intermediate hemiketal species, from whichcis-andtrans-chalconesare obtained.7 Comparison withother flavylium com- pounds shows that the hydration process is affected by the amino group and that the hydroxyl group is implicated in tautomerization and isomerization reactions. An experimental and computational (quantum chemical and FMO) study of ring- chaintautomerismofsimplifiedanaloguesofoxidizedandreducedisoniazid–NAD(P) adducts has identified when cyclic hemiamidal and keto-amide chain forms will pre- dominate, respectively; the dependence on the aryl ring and on solvent polarity has been discussed.8 Pyrrolidine(20 mol%)-catalysedaldolreactionoftrifluoroacetaldehydeethylhemi- acetal with ketones or aldehydes at room temperature has been shown to afford the aldolproductsingoodtoexcellentyields(upto95%)andwithmuchhighercatalytic activity than piperidine. It is suggestedthat the reaction proceeds by rate-determining formation of intermediate enamine which is present in extremely low concentration (cid:4)ee during the reaction; the asymmetric aldol reaction with cyclohexanone catalysed by l-proline derivatives was also discussed.9 Scheme 5 depicts the generally accepted cycle (via the ‘outer route’ depicted by the dashedarrows) of proline-catalysed reactions of aldehydes andketones with elec- trophiles,inwhichoxazolidinones(15)and(18)appeartoplayaroleonlyas‘parasitic’ species not involved in any steps for formation of product or reactive intermedi- ates. A detailed study of oxazolidinones has now revealed direct evidence of the two