Organic Reaction Mechanisms 1974

658 Pages·1976·24.413 MB·English

ORGANIC REACTION MECHANISMS
* 1974
ORGANIC REACTION
.
MECHANISMS 1974
An annual survey covering the literature
dated December 1973 through November 1974
Edited by
A. R. BUTLER, University of St. Andrews
M. J. PERKINS, Chelsea College, University of London
An Interscience" Publzcarion
JOHN WILEY & SONS
- - -
London New York Sydney Toronto
An Interscience@P ublication
Copyright 0 1976b y John Wiley & Lrd.
Sons
All rights reserved. No part of this publication may be reproduced, stored
in a retrieval system, or transmitted, in any form or by any means, elec-
tronic, mechanical, photocopying, recording or otherwise, without the
prior written permission of the Copyright owner.
Library of Congress Catalog Card Number
66-23143
ISBN o
471 126934
Printed in Great Britain by
William Clowes & Sons Limited
London, Colchester and Beccles
Contributors
M. S. BARD Department of Organic Chemistry, University of
Newcastle-upon-Tyne
R. BAKER Department of Chemistry, The University, South-
ampton
T. W. BENTLEY Department of Chemistry, University College of
Swansea
R. B. BOAR Department of Chemistry, Chelsea College, University
of London
A. R. BUTLER Department of Chemistry, The University, St.
Andrews
B. CAPON Department of Chemistry, Glasgow University
M. R. CRAMPTON Department of Chemistry, Durham University
A. C. KNIPE Department of Chemistry, The New University of
Ulster
G. V. MEEHAN Department of Chemistry and Biochemistry, James
Cook University of North Queensland, Australia
D. C. NONHEBEL Department of Pure and Applied Chemistry,
University of Strathclyde
M. I. PAGE Department of Chemistry, The Polytechnic, Hudders-
field
M. J. PERKINS Department of Chemistry, Chelsea College, University
of London
B. V. SMITH Department of Chemistry, Chelsea College, Uni-
versity of London
I. D. R. STEVENS Department of Chemistry, The University, South-
ampton
J. C. WALTON Department of Chemistry, St. Salvator’s College,
University of St. Andrews
W. E. WATTS School of Physical Sciences, The New University of
Ulster
Preface
This volume, continuing the general pattern now established for the series, covers
literature actually dated December 1973 to November 1974. The principal aim is a
general summary of the progress of work on organic reaction mechanism, rather than a
detailed evaluation of selected topics ; therefore, some sections are inevitably somewhat
fragmentary, but all are concise, although our contributors are encouraged to emphasise
results which appear at the time to represent major advances.
Since this is the tenth volume in the series, we have incorporated a second quinquennial
subject index and would like to thank Terry Jenkins and Elizabeth Leitch
(1970-74),
for their major contributions to the demanding task of preparing this.
Unfortunately, owing to circumstances beyond his control, Dr. Meehan was unable to
complete the Chapter on Molecular Rearrangements by our normal deadline ; however,
with his help we have been able to compile a survey which we hope affords adequate
coverage of this important topic. In doing this we have been fortunate to have the
sympathetic and expert co-operation of the British office of John Wiley and Sons, who
also have once again done everything possible to expedite the rapid publication of this
book.
August 1975 A.R.B.
M.J.P.
Con tents
1. Reactions of Aldehydes and Ketones and their Derivatives by B. CAPON 1
2. Reactions of Acids and their Derivatives by M. I. PAGE . . 23
Radical Reactions by D. C. NONHEBEaLnd J. C. WALTON . . 69
3.
4. Oxidation and Reduction by T. W. BENTLEY . . 187
5. Carbenes and Nitrenes by M. S. BAIRD . . 223
. .
6. Nucleophilic Aromatic Substitution by M. R. CRAMPTON 249
7. Electrophilic Aromatic Substitution by B. V. SMITH . . 269
8. Carbonium Ions by R. BAKER . . 293
9. Nucleophilic Aliphatic Substitution by I. D. R. STEVENS . . 327
.
10. Carbanions and Electrophilic Aliphatic Substitution by R. B. BOAR 377
. .
11. Elimination Reactions by A. C. KNIPE 399
12.1. Addition Reactions I. Polar Addition by A. C. KNIPE . . 421
12.11. Addition Reactions II. Cycloaddition by W. E. WATTS. . 441
13. Molecular Rearrangements by A. R. BUTLERG, . V. MEEHAN and M. J.
PERKINS . . 455
Author Index, 1974 . . 509
Subject Index, 1970-74 . . 566
Errata . . 660
Errata for Organic Reaction Mechanisms 1969
P. 346, 9 lines from the bottom : Fur MnIII read Mn".
Errata for Organic Reaction Mechanisms 1970
P. 150: The solvent for the reaction should be triglyme, not THF.
Errata for Organic Reaction Mechanisms 1973
P. 345: In formula (37)t he bond from phosphorus should be to C-2 of thiophen, and not C-3 as
to
shown.
660
Organic Reaction Mechanisms 1974
Edited by A. R. Butler, M. J. Perkins
Copyright © 1976 by John Wiley & Sons, Ltd.
CHAPTER I
Reactions of Aldehydes and Ketones and their
Derivatives
B. CAPON
Chemistry Department, Glasgow University
.
Formation and Reactions of Acetals and Ketals - 1
.
Hydrolysis and Formation of Glycosides . 4
.
Non-enzymic Reactions - 4
Enzymic Reactions . . . - 5
.
(a) Glucoeidasea . 5
.
(b) Lysozymes
(c) Galactoeidmes . . . * . -- 65
. . . .
(d) Amylases. - 6
. . .
(e) Other Glycosidases - 6
.
Hydration of Aldehydes and Ketones and Related Reactions * 7
. . .
Reactions with Nitrogen Bases
SchiEBmes . . . . 8
Enamines . . . . . . . . .- 89
. . . , . .
Nucleosides and Glycosylaminea 10
.
Hydrazones, Oximes, Semicarbazones and Related Compounds 10
. . . .
Hydrolysis of Enol Ethers 10
. . . .
Enolization and Related Reactions 11
. . . . .
Homoenolization 14
Aldol and Related Reactions . . . . 14
. * . . .
Other Reactions 15
References . . , . . . . 16
Formation and Reactions of Acetals and Ketalsl-3
Craze and Kirby4 have studied the hydrolysis of a series of 4- and 5-substituted
acids and analysed the results by Jafft5’s method to
2-(methoxymethoxy)benzoic (1)
yield values of pphenol= 0.89 and pcarboxy = 0.02 for the spontaneous hydrolysis of the
H
1
2 Organic Reaction Mechanisms 1974
un-ionized form. The small value of pearboxy suggests that there is little proton transfer
in the transition state which is not consistent with a mechanism (2) in which the ionized
form undergoes a rapid specific acid-catalysed hydrolysis owing to an electrostatic
effects as here the proton should be completely transferred in the transition state. A
mechanism involving intramolecular general-acid catalysis with a small amount of
proton transfer seems more reasonable.5
It has been suggested that the hydrolysis of o-hydroxybenzaldehyde diethyl acetal
involves intramolecular catalysis.6 Unfortunately, the rate constant was not compared
with that for the corresponding para-compound and so it is difficult to judge this claim.
The corresponding were studied in 1963 by Bender and
2-(hydroxyphenyl)-l,3-dioxans
Silver7 who concluded that there was no intramolecular catalysis in the hydrolysis of
the ortho-compound as it and the para-analogue reacted at very similar rates. The
anion of o-hydroxybenzaldehyde diethyl acetal also undergoes measurable hydrolysis
with kn/kH = 0.469; spontaneous ionization with a transition state (3) is a reasonable
mechanism.6
It has been shown that hydrolysis of the four-membered cyclic acetal(4), like that of
similar three-membered ones,8 is general-acid catalysed.9 Presumably ring opening is
such an easy process that it starts on only partial transfer of a proton. The hydronium-
ion-catalysed hydrolysis of the three-membered compound (5) is about ten times faster
than that of (4), and the solvent isotope effects are k(D30+)/k(H30+)= 2.02 and
1.8(+0.9), respectively. At high pH, dehydration of the hemiacetal is the rate-limiting
step (see p. 8).
General-acid catalysis has been detected in the conversion of the spiro-Meisenheimer
complex (6) into (7).10 This reaction stands in a logical sequence since it has been shown
that increasing the stability of the intermediate carbonium ion formed from an acetal
causes the reaction to become general-acidc atalysed.11 Since (6) is negatively charged
the fragment which corresponds to a carbonium ion is uncharged and so the detection
of general-acid catalysis in the conversion of (6) into (7) is not unexpected. It is
interesting that decomposition of the 1,l-diethoxy-complex (8) is not general-acid
catalysed.
Reactions of Aldehydes and Ketones and their Derivatives 3
The hydrolysis of tetrahydro-2-( p-toly1thio)pyran is not general-acid catalysed. The
plot of logk,b, against Ho is a straight line with slope -1.10 in hydrochloric acid and
-1.19 in perchloric acid. The solvent isotope effect is k(D30+)/k(H30+)= 1.3, the
entropy of activation +7.4 cal mol-1 K-1, and the p-value for hydrolysis of a series of
tetrahydro-2-(p -substituted pheny1thio)pyrans is -0.96. An A-I mechanism which
involves rate-limiting carbon-sulphur bond fission was proposed. The mercuric-ion-
promoted reaction was also studied.'%
Acid hydrolysis of is about 50 times slower
2,2-diphenyl-4-(2-piperidyl)-l,3-dioxolan
than that of presumably because of the electrostatic effect
2,2-diphenyl-l,3-dioxolan,
of the protonated piperidyl residue.12b The hydrolyses of 4,4-dimethyl-l,3-dioxan in
aqueous dioxan,12c of diethyl acetal catalysed by ferric i0ns,13* and of the acetals
formed from substituted diphenylacetaldehydes and ethylene glycol13b have been
studied.
It has been shown that the hydronium-catalysed hydrolyses of substituted aceto-
phenone dimethyl acetals do not yield a linear Hammett plot when u+ constants are
used.13c This behaviour is similar to that reported for the hydrolysis of substituted
benzaldehyde diethyl acetals in 50% aqueous dioxan14 but differs from that reported
for their hydrolysis in water15 (see also p. 10).
If the group R of dioxolans (9) is changed from H to Ph there is only a four-fold
increase in the rate of hydrolysis. The rate constants for the hydrolysis of (9) with
R = substituted phenyl are not correlated by the U+ or u constants. Application of the
(9) (10) (11)
Yukawa-Tsuno equation leads to a p-value of -2.9 which is only slightly less than that
for the hydrolysis of benzaldehyde diethyl acetals (p = -3.35). This suggests that the
small effect of introducing a phenyl group does not arise mainly because there is steric
inhibition to conjugation of this group with the developing carbonium ion in the transi-
tion state, but from some other effect. It was suggested that this was steric interaction
of the 2-methyl group with the dioxolan ring.16
General-acid catalysis has been detected in the hydrolysis of the orthoesters and
(10)
The catalytic constants for hydrolysis of are about forty times greater than
(11). (11)
for This contrasts with the results obtained with the acyclic orthoesters where the
(10).
phenyl-substituted compound reacts more slowly than the unsubstituted one. It was
suggested that the latter result arose from steric inhibition of resonance because of
steric interaction, absent in compound between the methoxyl and the phenyl
(ll),
groups.17 It would be interesting if the p-value for hydrolysis of were compared
(11)
with that for the hydrolysis of trimethyl orthobenzoate.
The heats of hydrolysis of some orthoesters have been measured and their heats of
formation calculated. There is a stabilizing interaction of 6-7 kcal mol-1 when three
alkoxy-groups are attached to a single carbon atom.la
The hydrolysis of ortho-thio-esters has been studied.10
Hydrolysis of the acylals and has been studied. The reactions are
(12), (13) (14)
specific-acid and general-base catalysed and also show a pH-independent reaction. The
entropy of activation and the variation of rate-constant with acid concentration suggest
that the mechanism of the acid-catalysed hydrolysis of is A2, presumably with
(12)