Organic Reaction Mechanisms·2000: An Annual Survey Covering the Literature Dated December 1999 to December 2000

666 Pages·2004·5.17 MB·English

OrganicReactionMechanisms(cid:127)2000:AnAnnualSurveyCoveringtheLiteratureDatedDecember
1999toNovember2000.EditedbyA.C.Knipe
Copyright2004JohnWiley&Sons,Ltd.ISBN:0-470-85439-1
·
ORGANIC REACTION MECHANISMS 2000
ORGANIC REACTION
·
MECHANISMS 2000
An annual survey covering the literature
dated December 1999 to December 2000
Editedby
A. C. Knipe
University of Ulster
Northern Ireland

AnInterscience Publication
Copyright2004 JohnWiley&SonsLtd,TheAtrium,SouthernGate,Chichester,
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Contributors
C. T. BEDFORD Department of Chemistry, University College, London,
W1M 8JS
D. C. BRADDOCK Department of Chemistry, Imperial College London,
South Kensington, London, SW7 2AZ
M. CHRISTLIEB Inorganic Chemistry Laboratory, University of Oxford,
South Parks Road, Oxford, OX1 3QY
A. J. CLARK Department of Chemistry, University of Warwick,
Coventry, CV4 7AL
R. G. COOMBES Department of Biological Sciences, Brunel University,
Uxbridge, Middlesex, UB8 3PH
M. R. CRAMPTON Chemistry Department, The University, Durham,
DH1 3LE
N. DENNIS University of Queensland, PO Box 6382, St Lucia,
Queensland 4067, Australia
A. DOBBS School of Chemistry, University of Exeter, Stocker
Road, Exeter, EX4 4QD
J. V. GEDEN Department of Chemistry, University of Warwick,
Coventry, CV4 7AL
E. GRAS Laboratoire de Synthese et Physico-Chimie des
Molecules d’Interet Biologique, Universite Toulouse,
III-Paul Sabatier, Toulouse, France
T. C. T. HO GlaxoSmithKline,OldPowderMills,Leigh,Tonbridge,
Kent TN11 9AN
D. M. HODGSON Dyson Perrins Laboratory, University of Oxford, South
Parks Road, Oxford, OX1 3QY
A. C. KNIPE SchoolofBMS,TheUniversityofUlster,Coleraine,Co.
Londonderry, BT52 1SA
P. KOCˇOVSKY´ Department of Chemistry, The Joseph Black Building,
The University of Glasgow, Glasgow, G12 8QQ
R. A. McCLELLAND Department of Chemistry, University of Toronto, 80 St
George Street, Toronto, Ontario M5S 1A1, Canada
N. P. MURPHY Department of Chemistry, University of Warwick,
Coventry, CV4 7AL
A. W. MURRAY Chemistry Department, The University, Perth Road,
Dundee, DD1 4HN
B. MURRAY Department of Applied Science, IT Tallaght, Dublin
24, Ireland
J. SHORTER 29 Esk Terrace, Whitby, North Yorkshire, Y021 1 PA
v
Preface
Thepresentvolume,thethirty-sixthintheseries,surveysresearchonorganicreaction
mechanisms described in the literature dated December 1999 to December 2000. In
order to limit the size of the volume, it is necessary to exclude or restrict overlap
with other publications which review specialist areas (e.g. photochemical reactions,
biosynthesis, electrochemistry, organometallic chemistry, surface chemistry and het-
erogeneous catalysis). In order to minimize duplication, while ensuring a compre-
hensive coverage, the editor conducts a survey of all relevant literature and allocates
publications to appropriate chapters. While a particular reference may be allocated
to more than one chapter, it is assumed that readers will be aware of the alternative
chapterstowhichaborderlinetopicofinterestmayhavebeenpreferentially assigned.
There have been several changes of authorship since last year, with the welcome
addition of co-authors (Drs J. V. Geden, A. W. Murphy, and T. C. T. Ho) and the
replacement of two authors who have made a major contribution to the series: Drs
R. A. McClelland and D. C. Braddock take over from R. A. Cox and B. Davis as
authors of ‘Carbocations’ and ‘Oxidation and Reduction’, respectively.
However, the most notable change to the team is the departure of my erstwhile
co-editor Prof W. E. Watts. We assumed joint editorship of the series in 1977, from
Tony Butler and John Perkins, and as colleagues at the University of Ulster were
well placed to share the editorial demands. Throughout this period it was a pleasure
to work with Bill, who displayed his characteristic prompt, thorough, and exacting
approach combined with sociable good humour at all times. Bill first contributed to
ORM in 1974 and his departure marks a 25 year period of unrivalled dedication to
the series.
Once again 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 publication are sustained.
A.C.K.
vii
CONTENTS
1. Reactions of Aldehydes and Ketones and their Derivatives by
B. A. Murray........................................................ 1
2. Reactions of Carboxylic, Phosphoric, and Sulfonic Acids and their
Derivatives by C. T. Bedford......................................... 45
3. Radical Reactions: Part 1 by A. J. Clark, J. V. Geden, and N. P. Murphy 115
4. Radical Reactions: Part 2 by A. P. Dobbs and T. C. T. Ho............. 149
5. Oxidation and Reduction by D. C. Braddock.......................... 179
6. Carbenes and Nitrenes by D. M. Hodgson, M. Christlieb and E. Gras... 209
7. Nucleophilic Aromatic Substitution by M. R. Crampton............... 229
8. Electrophilic Aromatic Substitution by R. G. Coombes................ 239
9. Carbocations by R. A. McClelland.................................... 249
10. Nucleophilic Aliphatic Substitution by J. Shorter...................... 277
11. Carbanions and Electrophilic Aliphatic Substitution by A. C. Knipe... 307
12. Elimination Reactions by A. C. Knipe................................ 351
13. Addition Reactions: Polar Addition by P. Kocˇovsky´................... 375
14. Addition Reactions: Cycloaddition by N. Dennis...................... 427
15. Molecular Rearrangements by A. W. Murray......................... 475
Author index........................................................ 601
Subject index........................................................ 643
ix
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OrganicReactionMechanisms(cid:127)2000:AnAnnualSurveyCoveringtheLiteratureDatedDecember
1999toNovember2000.EditedbyA.C.Knipe
Copyright2004JohnWiley&Sons,Ltd.ISBN:0-470-85439-1
CHAPTER 1
Reactions of Aldehydes and Ketones and their Derivatives
B. A. MURRAY
DepartmentofAppliedSciences,Institute ofTechnologyTallaght,Dublin,Ireland
FormationandReactionsofAcetalsandRelatedSpecies ............... 1
ReactionsofGlucosidesandNucleosides........................... 3
ReactionsofKetenes......................................... 4
FormationandReactionsofNitrogenDerivatives .................... 5
Imines ................................................. 5
IminiumIonsand RelatedSpecies............................... 8
Oximes,Hydrazones,andRelated Species ......................... 8
C−CBondFormationandFission:AldolandRelatedReactions ......... 10
Regio-,Enantio-,and Diastereo-selectiveAldolReactions ............... 10
TheMukaiyamaAldol....................................... 11
OtherAldol-typeReactions ................................... 12
Allylations............................................... 14
Other AdditionReactions ..................................... 15
Generaland Theoretical...................................... 15
Protonation .............................................. 16
Hydration ............................................... 16
AdditionofZincReagents .................................... 17
AdditionofOtherOrganometallics .............................. 18
TheWittigReaction,and Variants ............................... 19
AdditionofOtherCarbonNucleophiles ........................... 22
MiscellaneousAdditions ..................................... 24
EnolizationandRelatedReactions ............................... 25
Enolates ................................................ 27
OxidationandReductionofCarbonylCompounds ................... 27
OxidationReactions ........................................ 27
Regio-,Enantio-,and Diastereo-selectiveReductions .................. 28
OtherReductionReactions.................................... 31
Atmospheric Chemistry....................................... 32
Other Reactions ............................................ 33
References ................................................ 35
Formation and Reactions of Acetals and Related Species
A simple hemiacetal has been stabilized by pressure.1 Acetone and propanol react to
give 2,2-dimethoxypropane: if the reaction is carried out with 1:1 dilute reactants
in THF, the hemiacetal is formed quantitatively at pressures above 2 GPa (20 atm).
1
2 OrganicReactionMechanisms2000
All thermodynamic functions have been reported for the reaction, as functions of
temperature and pressure.
3-(Hydroxymethyl)-5-methylsalicylaldehyde(1,oritsacetonide)undergoesastereo-
selectivecyclotetramerizationtoyield the S -symmetric (R,S,R,S)-tetraacetal(2), the
4
most thermodynamically stable of the four possible diastereomers.2 (cid:1)
de
Me
Me
O
OH OH O
O
H
H O H
O O
H O
H
O
Me
O
(1) Me
Me
(2)
9-Phenyl-1-thia-5-oxaspiro[5.5]undecane, a spiro-1,3-oxathiane prepared from 4-
phenylcyclohexanoneand3-mercaptopropan-1-ol,existsasamixtureofdiastereomers,
(3-cis) and (3-trans), with the phenyl acting as a ‘holding group’ on the cyclohexane
ring.3 Rate and equilibrium data have been reported for the isomerization in CDCl
3
solution via an open-chain form, i.e. a ring–chain tautomeric equilibrium.
S O
(3-cis) (3-trans)
Ph O Ph S
Formaldehyde acetals, R1OCH OR2, are increasingly employed as fuel additives.
2
Their fate in the atmosphere has been investigated in studies of the rate of reaction
withhydroxyl radicals.4 They showhigher reactivitythanethers or alcohols,withthe
main degradation pathway being initiated by OH attack at the α-carbon of one or
other R group.
The relative rates of hydrolysis of a range of aldehyde-and ketone-derived acetals,
orthoesters, and orthocarbonates have been compared with each other and with the
related six-membered cyclic and six, six-membered spiro analogues, with a view to
separating out steric, inductive, and stereoelectronic effects.5
The roles of solvent, catalyst, and sonication have been studied in the acetalization
of D-gluconolactones with long-chain aldehydes.6
For selective hydrolysis of hydrazones without affecting acetals, see Hydrazones
below.
1 ReactionsofAldehydesandKetonesandtheirDerivatives 3
Reactions of Glucosides and Nucleosides
Manyalcoholswhichcanbechemicallyglycosylateddonotreactintheβ-glucosidase-
mediated enzymatic reaction. A computation approach correlates the reactivity of the
alcohol (in the enzymatic case) with its nucleophilicity: the charge on the reacting
atom is an excellent predictor.7a Using a simplified model of the enzyme active site,
transition-state energies have been calculated in two cases. Cyclohexanol, a typi-
cal ‘reacting’ alcohol, was found to have an activation energy of 1.3 kcalmol−1,
whereas that of phenol (‘non-reacting’) is calculated to be 15.8 kcalmol−1. In terms
of charge, the reacting alcohol with the lowest calculated charge (benzyl alcohol)
is ca 0.1 electrons more charged than the non-reacting case with the highest charge
(p-methoxyphenol). In substantiation of this predictive method, three alcohols which
were calculated to be reactive were found to be so, contrary to results of a previous
study.7b
N-Acetylxylosamidoxime (4) has been synthesized: it is intended to use it and
derivatives thereof as transition-state analogues for glycosyltransferases specific to
N-acetylglucosamines.8
OBn
HN
O
H N OBn
NHAc
(4)
A range of glycosyl transfer reactions designed to favour intramolecular (1,x)-
shifts (x =3,4,5,9) proceed via intermolecular pathways only.9 Stereocontrolled gly-
cosyl transfer reactions, using unprotected glycosyl donors, have been reviewed (87
references).10
The kinetics and mechanism of reaction of bromo- and chloro-malonaldehydes
withadenosineinaqueoussolutionhavebeenstudied.11 Suchaldehydesareknownto
arise intracellularly from mutagenic bifunctional halo compounds. The etheno prod-
ucts that they yield with nucleobases are also useful tools in nucleic acid chemistry,
owing to their fluorescence and, in some cases, the survival of the formyl function
for further derivatization. The reactions proceed through the attack of the exo-amino
group of adenine on the carbonyl carbon, and there are relatively small differences
between the chloro and bromo reactants, or between the malonaldehydes and the
more-studiedacetaldehydes.Themostefficientconditionsforformationoftheetheno
product (formed via a deformylation) and of the formyletheno product are described.
Ina theoreticalstudyofproton transferinthe mutarotationof sugars,2-tetrahydro-
pyranolwaschosenasamodelsugar.The rate-limitingstepofringopeninghasbeen
studied for two mechanisms: a high-energy intramolecular proton transfer and a low-
energy route using formic acid as catalyst.12 The latter process is a double proton
transfer reaction, concerted but asynchronous.
4 OrganicReactionMechanisms2000
Thekineticsandmechanismofspontaneousβ-glycosidehydrolysishasbeeninves-
tigated for a series of deoxy- and deoxyfluoro-2,4-dinitrophenyl-β-D-glycopyrano-
sides.13 Within this series, field effects on the O(5) substituent (i.e. the site of charge
development in the transition state) dominate: Hammett ρ values vary from −2.2
I
to −8.3 in the glucoside series, for example. Inter-series comparisons also involve
variations in steric and solvation effects.
Thekineticsoftheacetolysisofmethyl2,3,4,6-tetra-O-acetyl-D-mannopyranosides
catalysed by sulfuric acid have been reported for acetic anhydride/acid solution.14
Other reports describe a regioselective α-phosphorylation of aldoses in aqueous
solution,15 phosphorylation of D-aldo-hexoses and -pentoses with inorganic cyclotri-
phosphate,16anda1,2-trans stereoselectiveallylationof1,2-O-isopropylidene-protec- (cid:1)
de
tedglycofuranosides.17IntramolecularO-glycosidebondformationhasbeenreviewed
(95 references).18
Reactions of Ketenes
An ab initio study of the gas-phase reaction of hydroxyl radical with ketene indi-
cates three distinct mechanisms: (i) direct hydrogen abstraction to give water and
ketenyl(HCCO),achannelwhichdominatesathightemperatures;(ii) olefiniccarbon
addition; and (iii) carbonyl carbon addition.19 The results compare well with such
experimental data as are available, and the implications for atmospheric combustion
processes are discussed.
Preparation of ketene (5), by Wolff rearrangement from 4-diazo-3-isochromanone,
shows direct kinetic evidence for a non-carbene route.20
O
C
O
(5)
Atheoreticalstudyof keteneandits thioandselenoanaloguessuggeststhatallare
bestrepresentedbyneutralcumulenestructures,thatthelattertwoaremorereactive,and
thatthethioketeneiscloserinbehaviourtotheselenocompoundthantheoxocase.21
Carbon suboxide (O=C=C=C=O) is calculated to hydrate at the C=C bond,22
in contrast to hydration of ketene, where addition to C=O to give the 1,1-enediol
is favoured.
Methyltrimethylsilylketene acetalshave beenoxidizedwithurea–hydrogenperox-
ide to yield α-siloxy esters, using catalytic methyltrioxorhenium; treatment with KF
then gives the corresponding α-hydroxy esters.23
Mechanisms of 2+2-cycloaddition of ketenimine (H C=C=NH) and imine
2
(H C=NH) have been studied theoretically,24 and the chemistry of α-oxoketene
2
thioacetals has been reviewed (28 references).25