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Fluorosulfuric Acid as a Reaction Medium and Fluorinating Agent in Inorganic Chemistry.

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The nitrosyl fluoride adducts of pentafluorides (or the
nitrosyl salts of the hexafluoro acids) are formed by
elements whose maximum valence is five. If nitrosyl
fluoride-hydrogen fluoride contains some nitrogen dioxide (formed by hydrolysis), nitrosyl salts of oxyfluoro
acids, such as NOTeOFS and NOMoOFs, can also be
formed. Many interesting compounds are to be found
among the reaction products with various elements,
for example: CrF3.3 NOF.3 HF, which decomposes
stepwise into (N0)zCrFs and CrF3 1111, or nitrosyl hexafluorouranate(V) NOUF6, prepared by treating metallic
uranium, as well as UF4, UOZFZ,and UO3 with the
94 "C, 68 OC, or 52 "C products [9]. Nitrosyl hexafluorouranate(V) can be converted into UF6 or UF7NO
with fluorine or chlorine trifluoride, respectively.
Mercury(l1) fluoride, which is a particularly effective
reagent in chlorine-fluorine exchange reactions, is now
readily available through its preparation from NOF.
3 H F and mercury(1) fluoride, which can be precipitated
from aqueous solutions. A purely chemical route leads
from hydrogen fluoride to fluorine via nitrosyl fluoridehydrogen fluoride, meicury(I1) fluoride, and potassium
fluoroplatinate(IV), which can be decomposed pyrolytically above 500°C [31]:
+ NOCI
+
+ Hg2Fz +
3 HgF2 + KzPtCl6 +
HF
NOF+HCL
2 NOF
2 HgF2
K2PtFg
3HgC12
+ 2 NO
+ K2PtF6
Table 3. Reactions of NOF.3 HF in the liquid phase with various
elements
very fast;
fast;
slow; (+) surface reaction;
- no reaction up to 94 "C; [+I reaction above 94 "C)
++
(+++
+
I
Products
~
Products
~~
++
Be
Mg
(+)
[+I
B
A1
(+)
Ga
CGraphite Si, Ge, Sn
+
++
Pb
P4.Pred
As, Sb
Bi
S
Se, Te
(+)
CI, Br, I
-
+++
+++
++
++
Ti, Zr
BeFy2 NOF
MgFz
BFj.NOF
AIF3
GaF3
++
+
++
+
++
Ti(Zr)F4+
Ti(ZrlFa.2NOF
VF4.2NOF
Nb(Ta)F,.NOF
MoFs.NOF
CrF3.3NOF.3HF
WF6.NOF
UFsNOF
MnF3
FeFsNOF
+
+
AgFF
+
Zn(Cd)FZ
V
[+1
Nb, Ta [+I
Mo
[+I
Cr
W
++
+
Si(Ge, Sn)F4
Ge(Sn)F4.2 NOF
PbFz
PFsNOF
As(Sb)FS.NOF
BiF3
Se(Te)Fq.NOF
U
Mn
Fe
Co,Ni Pt
cu
Ag
Au
Zn, Cd
Hg
cuz
+++ HgzFz. HgFz
Nitrosyl fluoride dissolved in hydrogen fluoride can
also be decomposed electrolytically into fluorine and
nitric oxide.
The author wishes to thank the following organizations for
their support: Deutsche Forschungsgemeinschaft, Verband der Chemischen Industrie, Farbenfabriken Bayer,
and Badische Anilin- & Soda-Fabrik. Special thanks are
due to his coworkers for conscientiously carrying out
ofren difficult experiments.
+ 2KFtPtf2F2
~~
[31] M . Brill, Doctorate Dissertation, Universitat Saarbriicken,
1965.
Received: February 22nd 1965 IA 4591233 IE]
German version: Angew. Chem. 77, 689 (1965)
Translated by Express Translation Service, London
Fluorosulfuric Acid as a Reaction Medium and Fluorinating Agent
in Inorganic Chemistry
BY PROF. DR. A. ENGELBRECHT
INSTITUT FUR ANORGANISCHE UND ANALYTISCHE CHEMIE
DER UNIVERSITAT INNSBRUCK (AUSTRIA)
Fluorosulfuric acid is known both in aqueous solution and as the anhydrous compound. The
anhydrous acid exhibits electrical conductivity which indicates its autodissociation. Even
strong acids such as H2S04 or H a 0 4 behave as proton acceptors, i. e. as bases, in puorosulfuric acid. Volatile inorganic acid fluorides can be readily prepared using fluorosulfuric
acid as fluorinating agent.
1. Fluorosulfuric Acid in Aqueous Solution
Fluorosulfuric acid was first prepared in I892 by Thorpe
and Kirman [l] from sulfur trioxide and anhydrous hydrogen fluoride:
S03+HF
__
+
HS03F
.-
[I] T. E. Thorpe and W. Kirman, J. chem. SOC.(London) 1892,
921.
Angew. Chem. internat. Edit. 1 Vol. 4(1965)
No. 8
Since it reacts very vigorously with water, the compound was at first assumed to be hydrolysed instantaneously and completely in this medium:
HS03F
+ H20 +
H2SO4
+ HF
Many years elapsed before Traube [2] found salts of
fluorosulfuric acid to be fairly stable in aqueous solution
and the acid to be incompletely hydrolysed on slow
addition to water accompanied by cooling.
I21 W. Traube, Ber. dtsch. chem. Ges. 46, 2513 (1913).
64 1
Woolf [3] subsequently prepared pure aqueous solutions
of fluorosulfuric acid from its salts with the aid of a
strongly acidic ion exchanger. Hayek and Czaloun [4]
succeeded in preparing pure dilute aqueous solutioiis of
the acid from its anhydride, pyrosulfuryl fluoride S 2 O 5 F 2 .
The stability of the aqueous acid is comparable to that
of aqueous tetrafluoroboric acid, but is greater than that
of the complex fluoro acids of Group Va elements [3].
Conductivity measurements in very dilute solutions
indicate the dissociation
H S 03 F
+ H20 +
SO3F-
+ H3O+
When only limited amounts of water are present, it is
found that fluorosulfuric acid and water are in equilibrium with sulfuric acid and hydrogen fluoride.
The similarities between perchlorates and fluorosulfates
in respect to solubility and crystallographic properties
suggest that the ionic radii of the anions are comparable
and that solvation is analogous in both cases. This is
supported by a comparison of their ionic mobiiities
which can be derived from the equivalent conductivities.
The latter are 69 cm2,ohn-1 for ClO, and 71 cm2.ohm-1
for S O 3 F - , both at 25 "C.
The conductometric titration curve [3] of aqueous fluorosulfuric acid is practically identical with the neutralization curve for sulfuric acid, i.e. the two acids have
approximately the same strength in water.
The special properties of anhydrous fluorosulfuric acid
are best shown by a comparison with sulfuric acid. The
relatively low viscosity and low freezing point of anhydrous H S 0 3 F are particularly conspicuous. These properties are undoubtedly due to the presence of a smaller
number of hydrogen bonds.
290-317
10.37
1.8267
24.54
100
194
1 . 0 3 10-2
~
+
+ SO3F-
H2S03FC
(a)
Woo/f [3] has also considered the following dissociations:
+ H S O ; + F2 H S 0 3 F + H2F++ S2O6FHSO3F
(b)
(C)
[3] A . A . Woolf, J. chem. SOC.(London) 1954, 2840.
[4] E. Hayek and A . Czaloun, Mh. Chem. 87, 790 (1956).
[ 5 ] J. Bnrr, R. .
I
Gillespie,
.
and R . C . Thompson, Inorg. Chem. 3 ,
1149 (1964).
642
In order to avoid reduction of the peroxopyrosulfuryl
difluoride by the cathodic gases, the experiment was
carried out in vacuum diaphragm cells. This reaction
can be regarded as analogous to the formation of peroxodisulfates during the anodic oxidation of sulfuric
acid.
NH4+
< R b + = K+ < N a b =
Lik
< Ba2+ < Sr2+
This series is more or less the one expected from the size
and charge of the cations and agrees with their solvation
in sulfuric acid [7].
3. Acid-Base Reactions i n Fluorosulfuric Acid
Auto-dissociation of the fluorosulfuric acid must be
assumed to explain its conductivity which cannot be
further decreased by repeated purification [S,81 :
2 HS03F
This postulate has recently been confirmed by Dudley [6],
who succeeded in preparing peroxopyrosulfuryl difluoride by electrolysis of solutions of alkali metal fluorosulfates in fluorosulfuric acid:
The abnormally high mobility of the SO3F- ion is probably due to a proton transfer mechanism of the Grotthus
type, as postulated for water and sulfuric acid. The
H 2 S 0 3 F + ion likewise seems to obey this mechanism [ 5 ] .
Table 1. Comparison of fluorosulfuric and sulfuric acids.
162.7
-89.0
1.7264
1.56
ca. 120
184
1.085~
10-4
Hydrogen is the only gas evolved at the cathode during
electrolysis of fluorosulfuric acid, and the amount given
off is in agreement with that expected from Equation (a)
or (c). The observed fluorine migration towards the
anode can be reconciled only with Equation (a) or (b),
since for dissociation (c), the relative ionic mobilities
would lead to a movement of fluorine towards the
cathode. In addition, the electrolyte acts as an oxidizing
agent at the anode, in virtue, presumably, of the formation of peroxodifluorosulfate ions:
The equivalent conductivities of alkali metal and alkaline earth metal fluorosulfates [ 5 ] are very similar. This
observation shows that the current is carried mainly by
the fluorosulfate ions. The values indicate that solvation
increases in the sequence:
2. Anhydrous Fluorosulfuric Acid
Boiling point [ "Cl
Freezing point [ " C ]
Density at 25 "C [g/ml3]
Viscosity at 25 'C [cpl
Dielectric constant at 25 "C
Heat of formation (liq.), [kcal/molel
Specific conductivity at 25 O C
[ohm-' cm-11
but, on the evidence of electrolysis experiments, concludes
that they are at most of minor importance.
According to Equation (a), acids and bases in the fluorosulfuric acid system can be defined as substances which
increase the r e l a t i v e concentration of the fluorosulfate
acidium ion H2S03F+ or of the fluorosulfate ion, respectively.
The relative concentration of the fluorosulfate ion can
be increased by adding either a dissociating alkali metal
fluorosulfate or substances which act as proton acceptors
and therefore decrease the concentration of the fluorosulfate acidium ion.
Since even substances which are strong acids in water,
e.g. H 2 S O 4 or HC104, act as proton acceptors in fluorosulfuric acid, it must be assumed that true acids do not
[6] F. B. Dudley, J. chem. SOC.(London) 1963, 3407.
Angew. Chem. internat. Edit. Val. 4 (1965)I No. 8
exist in this medium. Acid behavior is to be expected
only from substances such as SbF5 which combine with
the SO3F- anion and therefore increase the relative concentration of the fluorosulfate acidium ion (see Table 2).
Table 2. Acids and bases in fluorosulfuric acid.
I Acids
Bases
Alkali and alkaline earth fluorosulfates
AsF~
SbF3
IFs
HC104
HzSO4
HF
while t h e conductivity expected from Equation (d) would be
substantially higher t h an t h e observed value.
On dissolution of AsF3 in fluorosulfuric acid, the conductivity increases gradually to reach a constant value in
about four days [5]. Titration of such solutions with
SbF5 in HS03F has shown that A s F 3 dissolves as a weak
base in accordance with equilibrium (f) proposed by
Barr et al. The increase in conductivity can then be explained by the secondary reactions (g) and (h) leading to
a fluorosulfate capable of dissociating.
AsFj
+ HSO3F +
+
+
A s F ~ HS03F
AsFz(SO3F)
Conductometric titrations with potassium fluorosulfate o r
antimony pentafluoride m ak e it possible to determine whether
a c om pound acts a s a n acid o r a s a base in fluorosulfuric acid.
Potassium fluorosulfate (in H S 0 3 F ) is added t o a solution
of the c ompound ! o be investigated (in HSO3F) and the
change in conductivity is recorded. If th e substance acts
a s a n acid, the latter is neutralized by th e fluorosulfate an d
the conductivity falls to a minimum. Neutralization, naturally,
represents the reverse of autoprotolysis:
H2SO3F+
+ SO3F- +
+ 2 HS 03F +
2 K+
+ HSO3F +
+ HS03F +
H3SO;
+ S03F
H2F'
+ SO3F-
The interpretation of th e behavior of perchloi-ic acid o r
potassium perchlorate in fluorosulfuric acid involves so me
difficulty. Woo!f[8]titrated a s3lution of perchloric acid i n
H S 0 3 F with antimony pentafluoride an d with potassium
fluorosulfate, a nd obtained a minimum in the first but not
in the second case. Nevertheless, he assumed equilibrium (d),
corresponding t o t h e well-known reaction of KCI04 with
HSO3F which leads t o perchloryl fluoride [9].
2 HSO3F
+ HCf04
ClO;
:5
+ H 3 0 + + 2 SO3F-
fd 1
O n the other hand, Barr et a / . [ S ] concluded from measurcments of the conductivity o f potassium perchlorate in fluorosulfuric acid tha t perchloric acid must be a very weak basic
electrolyte in accordance with Equation (e):
HC104
[7]
39,
[8]
[9]
+ H S 03F +
+SO3F
(h)
H2C10;
+ S03F-
(e)
J . Barr, R . 1. Gillespie, and E. A. Robinron, Canad. J. Chem.
1266 (1961).
A . A. Wool/, J. chem. SOC.(London) 1955,433.
G. Barth- Wehrenolp, J. inorg. nucl. Chem. 2, 266 (1956).
Angew. Chem. internat.
4. Fluorosulfuric Acid as a Fluorinating Agent
Fluorosulfuric acid is an excellent fluorinating agent for
the preparation of volatile inorganic acid fluorides and
fluorosulfates. Some acid fluorides prepared in this
manner are listed in Table 3.
Table 3. Preparation of acid fluorides with HSO3F.
During electrolysis of a solution of hydrogen fluoride in
fluorosulfuric acid, Woolf [8] observed a migration of
fluorine towards the cathode. This result and quantitative conductivity measurements are best explained by the
formation of H2Ff ions, even if only to a very small
extent, according to the following basic dissociation:
HF
AsFz+
(f)
(6)
Solutions of antimony trifluoride in HS03F have considerably higher conductivities and are even less stable
than solutions of AsF3 [ 5 ] . Antimony trifluoride also
behaves as a base, but forms secondary products relatively quickly even at room temperature. These secondary products then dissociate, probably in the same way
as postulated for A s F 3 .
+ 2 SO,F- + H2S04
Conductometric investigations point to a weakly basic
behavior of sulfuric acid in fluorosulfuric acid, characterized by a base constant Kb = 10-4, i.e. the following
equilibrium can be postulated:
H2S04
+
A s F ~ ( S O ~ F )H F
2 HS03F
The behavior of HzS04, HF, HClO4, and their salts in
fluorosulfuric acid gives a n indication of the strength of
the latter. On dissolution of potassium sulfate in fluorosulfuric acid, the conductivity observed is almost exactly
twice that of an equimolar solution of potassium fluorosulfate [ 5 ] . It follows that potassium sulfate is completely solvolysed in this medium:
K2S04
+
HA SF^+ + S03F-
Edit. Vol.4(1965)
1 No. 8
Starting material
Fluoride
KMn04
KzCr04 (CrO,, KzCrzOl)
P4010
Base04
AszOs (BaHAsO,)
As203
BaTe04
KC104
FMnO3
F2CrOz
F3PO
I-*SeO2
AsFs, (OAsF3)
AsF,
FsTeOH
FClOi
B.p. [ " C ]
60
30
-39
- 8
-53 (+24)
63
60
-46
When an alkali metal or alkaline earth metal salt of the
acid, or the acid anhydride, is introduced into fluorosulfuric acid, the fluoride is formed either instantaneously in the cold or gradually on heating or boiling. For
example, no perchloryl fluoride can be detected by NMR
spectroscopy in a cold solution of potassium perchlorate
in fluorosulfuric acid [16]. However, between 50 and
85 "C the product distils over in very good yield [9].
KC104
+ 2 HSOjF
-'
CIO3F
+ H2S04
I-
KSO,F
[lo] A . Engelbrecht and A . v. Grosse, J. Amer. chem. SOC. 76,
2042 (1954).
/ I 11 H . Afzwanger, Dissertation, Universitiit Innsbruck, 1953.
[I21 E. Hayek, A. Aignesberger, and A . Engelbrecht, Mh. Chem.
86, 735 (1955).
[13] A . Engclbrecht and B. Stoll, 2. anorg. allg. Chem. 292, 20
(1957).
1141 A. Engelbrecht, .A. Aignesbergei, and E. Hayek, Mh. Chem.
86, 470 (1955).
[15] A . Engelbrecht and F. Sladky, a) Angew. Chem. 76, 379,
(1964); Angew. Chern. internat. Edit. 3, 383 (1964); b) M h . Chem.
96, 159 (1965).
[I61 J. Bacon, R . J. Gillespie, and J. W. Quail, Canad. J . Chem.
41, 3063 (1963).
643
Woolf [8] has postulated the following reactions :
3 HS03F
ClO;
+ KC104 +
+ SO3F- +
+ 3 SO3F- + H3O + K+
+ SO3
ClO;
C103F
according to which perchloryl fluoride is formed by the
thermal decomposition of the ion pair ClO: S03F-.
fluorosulfuric acid, which leads not only to varying
amounts of AsF5 and probably AsOF3, but also toamixture of AsFz(S03F)3 and AsF3(S03F)2 [12]. The
reaction of H4BaTeO6 with HS03F shows that the fluor
rosulfates of metals in high oxidation states can be
relatively stable: the compound FsTeOS02F is obtained
in very good yield [15b].
The analogous reactions which lead to Mn03F and
Cr02F2 [lo, 111are instantaneous, and formation of the
oxide fluorides is accompanied by the evolution of a
considerable amount of heat.
It is worth noting that all the compounds prepared in this
manner are highly volatile, and complete conversion is
generally obtained only by removal of the acid fluorides
already formed. This indicates equilibria which may be
intrinsically unfavorable for the formation of acid fluorides,
but which can be displaced by the volatility and the relatively
low solubility of the reaction products in fluorosulfuric acid.
The preparation of SeOzFz from barium selenate and fluorosulfuric acid involves complete solvolysis (i) as the primary
stage, followed by the protolysis (k) of the selenic acid, which
probably behaves as a base towards to fluorosulfuric acid:
5. Salts of Fluorosulfuric Acid
Alkali, alkaline earth, and ammonium fluorosulfates
have been known for a long time [2]. A much used
general method of preparation is the reaction between
metal fluorides and sulfur trioxide [3,17-201:
MF+SO3
+
MOS02F
An alternative procedure is based on the reaction of
fluorides [21] or chlorides [19,22,23] with fluorosulfuric
acid, and is accompanied by liberation of H F or HCI.
However, chloride-, fluoride- and oxide fluorosulfates
are sometimes formed during these reactions [19,23].
Elimination of water from the selenate acidium ion may represent the rate-determining reaction which is strongly temperature-dependent.
The last step is then probably the decomposition of the
resulting ion pair HSeO; S03F-, leading to formation of SO3,
which combines with the water formed in Eq. (I) to give
sulfuric acid:
HSeO; SO3F-
+
HSe03F
MClx
+ x H S O ~ F -+
MFx-y(S03F)y
+ (x-Y)HCI + yHSO3C1
M = Th4+, Zr4+
+ SO3
An analogous repetition of this reaction sequence then leads
to the formation of selenium dioxide difluoride:
+ HS03F + HzSeO3Ff + SO3F+ H20 + SeOzF+
SeOzF+.SO3F- + Se02F2 + SO3
HSeO3F
6. Thermal Decomposition of Fluorosulfates
Unlike the thermally stable fluorosulfuric acid, many
fluorosulfates decompose at relatively low temperatures,
via the following types of reactions [12,19,20,24-261:
HzSeO3F+
All reactions listed in Table 3 formally represent the replacement of a hydroxy group by fluorine. A thermally
unstable fluorosulfate is indeed formed as an intermediate in addition to the acidium ion:
OnX-OH
+ HSOsF +
On-lX(OH)2+
+
+
+
OnX+ SO3F-
Hz0
On-1X(OH)z+
+ OnX+
OnXOS02F
+ SO3F-
(m)
(n)
(0)
Its thermal decomposition then leads to formation of the
acid fluoride. Evidently the elimination of water from
the acidium ion in accordance with Eq. (n) determines
the rate of formation of the acid fluoride, since Mn03F
and CrOZF2 are formed by very fast reactions. It is
well known that the acids H2Cr04 and HMn04 likewise form anhydrides relatively easily.
In some cases, the fluorosulfate itself is volatile and
thermally sufficiently stable to distil without decomposition. One example is the reaction of As205 with
644
__
-.
[17] W. Lunge, Ber. dtsch. chem. Ges. 60, 962 (1927).
1181 R. K . Iler, US.-Pat. 2 312 413 (March 2nd, 1943).
[191 E. Hayek, A . Czaloun, and B. Krismer, Mh. Chem. 87, 741
(1956).
[20] E. L . Muetterties and D. D . Coffman, J. Amer. chem. SOC.
80, 5914 (1958).
1211 A. Engelbrecht, unpublished work.
[221 0. Ruff, Ber. dtsch. chem. Ges. 47, 656 (1914).
[23] E. Hayek, J. Puschmann, and A. Czaloun, Mh. Chem. 85,
359 (1954).
[24] H. Jonas, Leverkusen (Germany), personal communication.
[25] H . A. Lehmann and L . Kolditz, Z . anorg. allg. Chem. 272,69
(1953).
[26] G. C. Kleinkopf and J. M. Schreeve, Inorg. Chem. 3, 607
(1964).
Angew. Chem. internat. Edit.
Yol.4 (I965) I No. 8
Pyrosulfuryl fluoride SzO5F2 [27], the anhydride of fluorosulfuric acid, is formed at low temperatures. Sulfuryl
fluoride is obtained by decomposition of S2O5F2 above
350 " C :
Sz05F2
f
Decomposition of fluorosulfates into SO3 and metal
fluorides occurs when fluoride formation is favored by a
particularly stable crystal lattice.
Received: April lst, 1965
SO3+S02F2
[A 4601236 IE]
German version: Angew. Chem. 77,695 (1965)
[27] E. Hayek u. W. Koller, Mh. Chem. 82, 940 (1951).
Translated by Express Translation Service, London
New Methods in Preparative Organic Chemistry IV [*]
New Reactions of Alkylidenephosphoranes and their Preparative Uses
Part 11. Alkylidenephosphoranes and Halogen Compounds [**]
BY PROF. DR. H. J. BESTMANN
INSTITUT FUR ORGANISCHE CHEMIE DER UNIVERSITAT ERLANGEN-NURNBERG (GERMANY)
The reactions of afkylidenephosphoranes with compounds containing ha(ogens can be used
to prepare ylides, which can be converted into usefulproducts, e.g. by hydrolysis, by thermal
decomposition, or by other reactions. Examples of such products are ketones (including
cyclic, unsaturated, and branched-chain ketones), carboxyiic esters (including those of
unsaturated, branched-chain, polyenecarboxylic, acetylenecarboxylic, and allenecarboxylic
acids), and aldehydes.
Contents :
Part 1. The Acid-Base Character of Phosphonium Sa!ts and
Alkylidenephosphoranes
A. Introduction
B. Phosphonium Salts and Alkylidenephosphoranes as
Conjugate Acid-Base Pairs
C. Transylidation
D. The Preparation of Phosphonium Salts and
A1kylidenephosphoranes
1. Phosphonium Salts
2. Alkylidenephosphoranes
Part I f . Alkylidenephosphoranes and Halogen Compounds
A. Introduction
B. Reactions Involving Transylidation
1. C-Acylation of Alkylidenephosphoranes
2. Reaction of Alkylidenephosphoranes with Esters of
Chloroformic Acid. Synthesis of Carboxylic Acids
3. Reaction with Organic Halides and Carbonium Salts
4. Reaction of Alkylidenephosphoranes with Halogens
C. Reactions Involving $-Elimination
1. The Mechanism of the Hofmann Degradation of
Quaternary Phosphonium Salts
2. Synthesis of Esters of P-Acylacrylic Acids
3. Synthesis of Esters of ct,$Unsaturated Carboxylic
Acids
D. Reactions Involving -{-Elimination
1. Reactio? of Allylidenetriphenylphosphoranes with
Esters of Chloroformic Acid. Preparation of Esters of
Polyenecarboxylic Acids
2. Synthesis of Esters of Allenecarboxylic Acid
E. Reactions of Alkylidenephosphoranes and Halogen
Compounds at a Molar Ratio of 1 :I
1. Synthesis of Esters of x-Branched-$Keto Acids
Angew. Chem. internat. Edit. 1 VoI. 4(1965) f No. 8
2. Reactions with Diazonium, Nitrilium, and Oxonium
Salts
F. Intramolecular Ring Closure
1. Monocyclic Compounds
2. Polycyclic Compounds
Part 1". Alkylidenephosphoranes and Reactants Containing
Multiple Bonds
A. Reaction with the Carbonyl Group (The Wittig Reaction)
B. Reaction with the C-C Double Bond
1. General
2. Formation of Cyclopropane Derivatives
3. Michael Addition
4. Synthesis of Pyran Derivatives
C. Reaction with the C-N Double Bond
1. Wittig-Typz Olefin Syntheses
2. Synthesis of Allenes
3. Reaction of Alkylidenephosphoranes with Phenyl
Isocyanate
D. Reaction with Esters of Acetylenedicarboxylic 4cid
E. Autoxidation of Alkylidenephosphoranes
I . Olefins from Primary Alkyl Halides o r Alcohols
2. Olefins and Ketones from Secondary Alkyl Halides or
Alcohols
3. Cyclization by Autoxidation of Bis-Ylides. Synthesis
of Monocyclic and Polycycilc Compounds
F. Oxidation with Peracids
G. Cleavage with Ozone
H . Other Reactions of Alkylidenephosphoranes
1. Reaction with Aliphatic Diazo Compounds
2. Reaction with Phenyl Azide
3. Reaction with Carbenes
4. Reaction of Ethoxycarbonylmethylidenetriphenylphosphorane with Epoxides
645
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