Organic Reaction Mechanisms · 2002: An annual survey covering the literature dated January to December 2002

653 Pages·2006·5.17 MB·English

·
ORGANIC REACTION MECHANISMS 2002
Organic R eaction Mechanisms · 2002: An annual survey covering the literature dated January to December 2002
Edited by A. C. Knipe  2006 John Wiley & Sons, L td. ISBN: 0-470-02203-5
ORGANIC REACTION
·
MECHANISMS 2002
An annual survey covering the literature
dated January to December 2002
Editedby
A. C. Knipe
University of Ulster
Northern Ireland

AnInterscience Publication
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Contributors
S. K. ARMSTRONG Department of Chemistry, University of Glasgow,
Glasgow, G12 8QQ
C. T. BEDFORD Department of Chemistry, University College Lon-
don, Gordon Street, London, WC1H 0AJ
A. BRANDI Department of Organic Chemistry Ugo Schiff, Univer-
sity of Florence, Sesto Fiorentino (FI), Italy
M. CHRISTLIEB Chemistry ResearchLaboratory, University of Oxford,
South Parks Road, Oxford, OX1 3QY
R. G. COOMBES Department of Biosciences, School of Health Sciences
andSocialCare,BrunelUniversity,Uxbridge,Middle-
sex, UB8 3PH
M. R. CRAMPTON Chemistry Department, The University of Durham,
Durham, DH1 3LE
N. DENNIS University of Queensland, PO Box 6382, St Lucia,
Brisbane, Queensland 4067, Australia
M. GENSINI Department of Organic Chemistry Ugo Schiff, Univer-
sity of Florence, Sesto Fiorentino (FI), Italy
E. GRAS Laboratoire de Synthe´se et Physico-Chimie des
Molecules d’Inte´re´t Biologique, Universite´ Toulouse,
III-Paul Sabatier, Toulouse, France
D. M. HODGSON Chemistry ResearchLaboratory, University of Oxford,
South Parks Road, Oxford, OX1 3QY
A. C. KNIPE School of Biomedical Sciences The University of
Ulster, Coleraine, Co. Londonderry, BT52 1SA
P. KOCˇOVSKY´ Department of Chemistry, The Joseph Black Building,
The University of Glasgow, Glasgow, G12 8QQ
R. A. McCLELLAND DepartmentofChemistry,UniversityofToronto,80St
George Street, Toronto, Ontario, M5S 1A1, Canada
R. N. MEHROTRA Department of Chemistry, JNV University, Jodhpur
342005, India
B. A. MURRAY Department of Applied Science, Institute of Technol-
ogy Tallaght, Dublin 24, Ireland
F. PISANESCHI Department of Organic Chemistry Ugo Schiff, Univer-
sity of Florence, Sesto Fiorentino (FI), Italy
J. SHORTER 29A Meadowfields, Whitby, North Yorkshire,
Y021 1QF
Preface
Thepresentvolume,thethirty-eighthintheseries,surveysresearchonorganicreac-
tion mechanisms described in the available literature dated 2002. In order to limit
the size of the volume, it is necessary to exclude or restrict overlap with other pub-
lications which review specialist areas (e.g. photochemical reactions, biosynthesis,
electrochemistry, organometallic chemistry, surface chemistry and heterogeneous
catalysis). Inorderto minimize duplication, while ensuringa comprehensive cover-
age, the editor conducts a surveyof all relevant literature and allocatespublications
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 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
organic synthesis, we now provide indication, in the margin, of reactions which
occur with significant diastereomeric or enantiomeric excess (de or ee).
Therehavebeentwochangesofauthorshipsincelastyear.DrR.N.Mehrotrahas
agreedtoalternatewithProf.K.K.Banerjiinreviewing‘OxidationandReduction’,
and the chapter on ‘Molecular Rearrangements’ has been divided into two parts,
written by Dr S. K. Armstrong and Prof. A. Brandi (with Drs M. Gensini and F.
Pisaneschi), respectively.
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
B. A Murray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. Reactions of Carboxylic, Phosphoric and Sulfonic Acids and their
Derivatives by C. T. Bedford . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3. Oxidation and Reduction by R. N. Mehrotra . . . . . . . . . . . . . . . . 105
4. Carbenes and Nitrenes by D. M. Hodgson, M. Christlieb and E. Gras 169
5. Nucleophilic Aromatic Substitution by M. Crampton . . . . . . . . . . . 195
6. Electrophilic Aromatic Substitution by R. G. Coombes . . . . . . . . . 209
7. Carbocations by R. A. McClelland . . . . . . . . . . . . . . . . . . . . . . . 223
8. Nucleophilic Aliphatic Substitution by J. Shorter . . . . . . . . . . . . . 261
9. Carbanions and Electrophilic Aliphatic Substitution by A. C. Knipe 297
10. Elimination Reactions by A. C. Knipe. . . . . . . . . . . . . . . . . . . . . 347
11. Addition Reactions: Polar Addition by P. Kocˇovsky´ . . . . . . . . . . . 373
12. Addition Reactions: Cycloaddition by N. Dennis . . . . . . . . . . . . . 411
13. Molecular Rearrangements: Part 1 (Pericyclic Molecular
Rearrangements) by S. K. Armstrong . . . . . . . . . . . . . . . . . . . . . 459
14. Molecular Rearrangements: Part 2 by A. Brandi, M. Gensini and
F. Pisaneschi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
Author index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581
Subject index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625
ix
CHAPTER 1
Reactions of Aldehydes and Ketones and their Derivatives
B. A. MURRAY
Department ofApplied Sciences,Institute ofTechnology Tallaght, Dublin, Ireland
Formation and Reactions of Acetals and Related Species . . . . . . . . . . . . . . 1
Reactions of Glucosides and Nucleosides . . . . . . . . . . . . . . . . . . . . . . . . . 4
Reactions of Ketenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Formation and Reactions of Nitrogen Derivatives . . . . . . . . . . . . . . . . . . . 7
Imines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Iminium Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Oximes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Hydrazones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
C−C Bond Formation and Fission:Aldol and Related Reactions . . . . . . . . 12
Regio-, Enantio-, and Diastereo-selectiveAldol and Related Reactions . . 12
The Mukaiyama Aldol and Related Reactions. . . . . . . . . . . . . . . . . . . 16
The Baylis–HillmanReaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Allylations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Other Addition Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
General and Theoretical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Additionof Organozincs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Additionof Other Organometallics . . . . . . . . . . . . . . . . . . . . . . . . . . 23
The WittigReaction and Variants. . . . . . . . . . . . . . . . . . . . . . . . . . . 24
MiscellaneousAdditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Enolization and Related Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
QuinoneMethides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Oxidation and Reduction of Carbonyl Compounds . . . . . . . . . . . . . . . . . . 30
Regio-, Enantio-, Diastereo-selective, and Other Reductions . . . . . . . . . 30
OxidationReactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
AtmosphericReactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Other Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Formation and Reactions of Acetals and Related Species
2,4,4,6-Tetrabromo-2,5-cyclohexadienone (1, TABCO) is an efficient and chemose-
lective catalyst for the acetalization (and transacetalization) of carbonyl compounds
and for the preparation of acetonides from epoxides and acylals from aldehydes.1
TABCO,formedinthebrominationofphenol,appearstoactthroughitsequilibrium
with the corresponding bromonium phenolate, a ‘non-traditional’ Lewis acid.
Organic R eaction Mechanisms · 2002: An annual survey covering the literature dated January to December 2002
Edited by A. C. Knipe  2006 John Wiley & Sons, L td. ISBN: 0-470-02203-5
1
2 Organic ReactionMechanisms 2002
O
Br Br
Si O
X
Br Br
(1) (2)
Results for diastereoselective nucleophilic substitution reactions of oxasilacy-
clopentane acetals (2, X=OMe, OAc, NR ) have been explained in terms of the
2
‘inside attack’ model for reactions of five-membered ring oxocarbenium ions.2 (cid:1)
de
Both α- and β-aminoacetals (e.g. 3) form dicationic electrophiles (4, cis–trans
mixture) in superacids, as observed by low-temperature NMR. These electrophiles
can react with benzene to give gem-diphenylamines (5).3
OMe H
N OMe N+ +OMe
H
(3) (4)
Ph
N Ph
(5)
α-Propargyl ethers have been prepared by two related methods: (i) reaction of
acetalswithallenylsilanesand(ii) athree-componentreactionofanaldehyde,alko-
xylsilane, and an allenylsilane.4 Both reactions are catalysed by Lewis acids.
Two mixtures, 1:2 Me SiNEt –MeI and 1:1 Et SiH–MeI, act as iodosilane
3 2 3
equivalents and can bring about ring-opening reactions on cyclic acetals and 1,3-
oxazolidines.5 For aromatic ketone ethylene acetals, they act as mild deprotection
agents.
Hydrogenation and alkylation of cyclic acetals have been reviewed, examining
variations in acetal structure and the influence of catalyst type on the rate and
direction of the process.6
Compound (6) is a symmetrical formaldehyde acetal of 4-hydroxybenzofuran-3-
carboxylic acid.7 Hydrolysis gives two molecules of 4-hydroxybenzofuran-3-carbo-
xylic acid, but this occurs in two steps. Initially, one acid product is formed, plus
cyclic acylal (7). The latter is then hydrolysed to give the second mole of product
1 Reactionsof Aldehydesand Ketonesandtheir Derivatives 3
(plus formaldehyde). pH–rate profiles for the two steps indicate that the most reac-
tiveformof(6)isitsmonanion,andthatthecarboxylateanionactsasanucleophile
to assist the generalacid-catalysedcleavageof the C−O bond to the leaving group,
inaconcertedfashion.Theneighbouringnucleophileparticipationenhancestherate
100-fold, out of a total enhancement of 105 over the rate expected for specific acid
catalysis. The implications for the mechanisms of lysozymes are discussed.
OH HO O
O O O O O O
O O O
(6) (7)
In a stereoselective investigation of ring opening of oxazolidines, the role of
n(N)→σ∗(C−O)electrondelocalization(i.e.anendo-anomericeffect)inthecleav-
age of the intramolecular C−O bond has been explored, as has the reduction in
reactivity – both hydrolytic and reductive ring opening – in N-acyloxazolidines.8
Bicyclo[4.1.0]heptan-7-one N,O-hemiacetals (8) undergo substitution by Wittig
reagents, Ph P=CHR3, to give 7-exo-amino-7-endo-substituted bicyclo[4.1.0]hep-
3
tanes (9) stereoselectively.9 An iminium cation intermediate is proposed.
HO R3H C
2
NR1R2 NR1R2
(8) (9)
Ratesofhydrolysisof1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine(10)inaque-
oussolutionarefirstorderinhydroniumion,withapH-independenttermcompeting
above pH 11.10 Reaction with hydrogen sulfide has also been characterized.
OH
R1 O
N N C
R2 S
HO N
OH
(10) (11)
4 Organic ReactionMechanisms 2002
Ketones and aldehydes can be protected as their 1,3-oxathiolane derivatives (11;
R1 =H, alkyl, aryl, R2 =alkyl, aryl).11 A new deprotection method, V O –H O -
2 5 2 2
◦
catalysed oxidation of NH Br in CH Cl –H O at 0–5 C, regenerates the carbonyl
4 2 2 2
very selectively. In particular, sensitive unsaturation in the R groups is not bromi-
nated. The mechanism presumably involves oxidation of bromide to Br+, which
reacts with sulfur, then subsequent hydrolysis.
Indium(III) triflate catalyses thio- and transthio-acetalization at ambient tempe-
rature.12
Lithium triflate catalyses dithioacetal formation from carbonyl derivatives in the
absence of solvent, typically in minutes.13 Using thiols or dithiols, acyclic or cyclic
productscanbeprepared,andthecarbonylreactantcanbefreeketonesoraldehydes,
or cyclic or acyclic acetals, or acylals. Significantly useful chemoselectivities are
reported.
N-Bromosuccinimide catalyses oxathio-, thio-, and transthio-acetalization of car-
bonyl compounds,14 while molten Bu N+Br− catalyses transthioacetalization of
4
O,O-acetals to S,S-acetals.15
Titanocenes have been used to promote conversion of thioacetals to terminal
alkenes with either a one- or two-carbon homologation, using ethylene as carbon
source in both cases.16 The reaction mode, metathesis versus β-elimination, can be
selected by adjusting the titanocene ligands.
Homoallylic thioethers have been prepared diastereoselectively via Lewis acid-
(cid:1)
promoted addition of chiral crotylsilanes to thioacetals of aldehydes, via thionium
de
ions.17
Reactions of Glucosides and Nucleosides
α-Thiogalactoside derivatives have been prepared by rearrangement of 1-O-(thio-
p-nitrobenzoyl) thiocarbonyl galactoside (12).18
OBn OBn
OBn
O R4
BnO NO2 R3 OR2 R5
OBn
O S BnO
R1
S O
(12) (13)
Stereoselective syntheses and reactivities of a range of (Z)-exo-glycals (13) have
(cid:1)
been reported.19 de
AstereocontrolledsynthesisofC-glycosideshasbeencarriedoutusingsamarium
diiodide mediation of a reductive coupling of epoxides of 1,2-anhydro sugars with
(cid:1)
carbonyl compounds; the stereoselectivity can be altered significantly by adding a
de
source of protons.20